I just looked and apparently you're not supposed to take the pillow or blanket either lol 💀💀 • Also I should clarify, this doesn't mean every headset using this double plug has noise cancellation. Delta just used the extra plug to make them both stereo to get extra channels to use for that. Other airlines might literally just use 2 mono plugs. • Also I didn't state this explicitly but the microphones are inside the headphones next to the speakers. That's why there are channels for it on the plug, so the noise signal can be sent to the computer to be processed. (By the way I did not actually take the pillow and blanket home. I just assumed you could because the blanket felt so remarkably crappy and cheap that I assumed it was disposable, then extrapolated for the rest of the items ¯\_(ツ)_/¯ . And the only reason I took the headphones was because I wanted to make a video about the plug lol. )
@@chiroyce If you mean those no-branded one you get in coach/economy class, they are so mass produced that most airlines won’t care if you take them. Now, for branded ones made by Bose or Sony you get in Business/first class, that’s a different story altogether.
I got some noise cancelling ars technica headphones like 10 years ago that came with this adapter... and I never even thought to look up what it's for.
The noise cancelling version is very recent. The old design was two mono plugs for the L and R channels, and all the adapters you can buy are dual mono. As to the reasons? It really was to prevent headphone theft and provide a revenue stream for headphone rentals. It was also an adaptation of the much older dual-prong tube headphones where the speakers were in the seats, and the sound transmitted via rubber tubes.
I used to work as a technician for Bose, many years ago, on their military noise cancelling headphones. The noise cancellation doesn't work well in these airline headphones because the microphones, being mounted away from the headphones, aren't picking up the ambient noise anywhere near your ears. Noise cancellation works by picking up the ambient noise entering your ears from outside of the headphones. Then it inverts the signal and mixes it with the headphone audio, thus, cancelling out the noise, but not the audio you want to hear. The amplitude, frequency, and phasing must be accurate for effective noise cancellation, and the best way to do that is to have the microphones as close to the ear as possible. Hard to explain, but I hope you get the jist of it.
@@masterman1502 why would you have noise cancelling headphones that aren't closed to begin with? First cancel as much as you can acoustically, then add active noise cancelling.
@@phaelox never doubted that. Though their probably still closed headphones. The only reason you'd want open headphones anyway is specifically so you'll hear something from outside.
Maybe in newer or updated planes these might be for noise cancelling, but when I use to fly between 2000-2012 it was so you'd buy the headphones airlines had for $5. They most certainly didn't have noise cancelling features as they were the most basic headphones with no padding much less over the ear design. Instead I bought a pair of 3.5mm adapters to convert the 2-prong plug to a single 3.5mm jack which allowed personal headphones to get both audio channels.
Yep, they wanted a way to grab more money from you with cheap, mass-produced off-the-shelf products. 2 mono 3.5mm jacks was the perfect solution. Now it's just the airline standard.
@@frostbite1991 it’s more that they started charging for something they used to give away, those plugs and headphones go back way farther than 2000. I remember listening to the ATC feed and bad music on these in the 90s.
@@AchieScottGraham I was just thinking when watching this, couldn’t be as simple as a way for them to send announcements to all the headphones regardless of what they are watching or listening to.
@@Olbaidon It's not. Since the audio you're listening to in this scenario is also controlled by the plane, they can absolutely just mix it in over the regular audio on the same channels, and/or pause the media. No need to run multiple source lines and do relatively expensive analog audio mixing on-device. They used to just be dual mono jacks (and still are, in other planes), which is why these headphones are broken out with one speaker and one mic on each side, rather than one input side and one output side, or, as was suggested, two separate audio sources.
They also could turn off the noise cancelling whilst announcements are being made (though they could pipe this over the audio circuit anyway). Or in the event of an incident, where cabin crew may be shouting instructions.
That's how they do it already, they interrupt what you're hearing through the headphones with their announcements. Pisses me off when I'm trying to watch a movie and they're busy thanking frequent fliers.
I am on the team that design those airplane headphone sockets. You are correct on almost all counts! The design of the plug is to minimise "pilfering" (theft) of the headphones. The connector format on the headphone and socket is described in the ARINC 628 standard. The plug you have there is a ARINC 628 - D2 plug. The noise cancellation actually happens in a small circuit inside the socket. So the microphone signal does not travel all the way to the IFE unit. When audio works on normal headphones this is a feature on some of the sockets. They they can detect that a normal headphone is plugged in and put an audio signal on the socket rather than use the signal for the noise cancelling. In the case of that socket you used on the plane I'm almost certain it is an IFPL brand socket which can have the sockets changed when they wear out too. Interesting to see you cover a topic I know very well.
So can one use a "normal" headphone (or a wireless bluetooth with noise cancellation one with a wireless adaptor) by plugging it into ONLY ONE of the 3,5 jacks?
@@ExarchNZ in that case i use the old trick of not inserting the whole thing but leave it halfway. Sure its mono, but at least you get both speakers and not one...
@@freeculture That works because you are connecting the R driver of your headset to the connector sleeve, which is normally a common GND inside the socket. The audio is referenced to this GND. So its like having the two drivers in series with each other sort of, which is also why it sounds quieter than normal when you do that. I guess in a pinch its better than nothing!
This design removes the need for more logic in the headphones, and probably also the need for a battery to drive the logic! Not sure an audio signal has enough power to supply logic circuits..
I got an airline adaptor for free with my Bose QuietComforts years ago, so I was aware that this was a thing. I've never used it though - the only time I've ever flown in a plane with in-flight entertainment (British Airways A380) they'd already transitioned to standard single-jack arrangements! I did bring it just in case though.
Interesting, I was on a British Airways flight to boston in a A380 in April. They still had the two-pronged plugs there. That was Economy+ tho, maybe they haven't phased it out for the masses or it depends on the individual planes.
@@arachn01d Ive occasionally used my adaptor on my old QuietComfort 15's. I've never had decent noise cancelling headphones in business class. I have in first but my own are still superior even to these. Always use your own high quality headphones for superior audio and hygiene.
Riding an airplane to Hawaii in the early '80s, the headphones did not use wires. Instead, the sound would travel through the air in rubber tubes to your ears.
@@nolongeramused8135 I don’t think it was that short lived. I’m 61 years old and I’ve flown several times a year since I was little kid and those tube style headphones were around until sometime in the 80s, or even later.
I really think the noise cancelling aspect has been a more recent development that has just taken advantage of the existing hardware. Sometime around the year 2000, Qantas switched from the pneumatic headphones to the 3.5mm jack with the dual pins. There's no way they were running an active noise cancelling computer for all the passengers 24 years ago. The idea of making them incompatible with most people's personal electronics makes a lot of sense. Especially 20-25 years ago, it would be silly not to pinch a pair of headphones at the end of your flight if it worked with your walkman/discman/Personal computer
I agree. These double connectors were around long before there were affordable noise cancelling headsets. Airlines wouldn’t spend the extra money if they didn’t have to. They might have added noise cancelling later (for first class passengers) but they didn’t start that way.
I have no idea IF, but noise cancellation is actually much simpler than you might imagine It does not need computers or other high-tech What it needs is a simple audio amplifier with all required attenuation to invert the phase of the incoming signal. Airlines could easily afford it since at least the 70s if they wanted, the device itself was affordable as soon as transistor amplifiers became commercially viable (although perhaps at not enough quality), but the idea of active noise cancellation itself didn't pick up until much later.
@@jwhite5008 with that in mind, it would make sense that they had a centralised noise cancelling feature that worked to remove engine noise. They can get loud, and the only way to give people a somewhat decent audio experience in that case is to try to minimize the engine noise. Also, by focusing on specific noises of the plane it probably makes the process a lot easier.
Seems plausible to me, that's the only way the pinout makes any sense to me. If you were designing this today and somehow thought two 3.5mm Jacks where the way to go, you would absolutely make one of the jacks use the normal TRS Left - Right - Ground pinout, and the other one Left Mic - Right Mic - Mic Ground. Then the headphone socket would be compatible with any old pair of headphones that the passengers bring on board. It probably wouldn't even need any extra consideration in the noise canceling module, since no mic signal should mean no cancellation signal is generated to mess with the audio. But if this was originally meant specifically to be incompatible, then this current iteration would just use the existing pinout, to be compatible with that old variant on existing planes, even if they don't use the noise canceling.
There is no additional processing. If you open a 3.5mm jack you will likely find switches. It is very easy to wire them in an arrangement making the mic line an actual output. Also some driver chips can probe impedance and/or voltage on line (mic is typically biased) so switching can be done just by toggling two MOSFETs.
@@Liggliluff apparently there is a bit more than that going on in active from what i've heard - a bit of digital delay or some other kind of DSP to account for the distance between drivers and your eardrums, among other things. "How Noise-Canceling Headphones Create Silence in Microseconds | WSJ Tech Behind " is a decent video explainer.
@@Liggliluff It's not that easy because the microphone signal is extremely weak. At a minimum you would need to amplify that signal by an amount dictated by the speakers that were connected. There is absolutely audio processing going on in ANC.
There’s no computer it goes to. Each chair has a tiny headphone amplifier/signal inverter. You have to think as cheap as possible. The microphone signal is inverted and combined with the incoming audio before being amplified. It’s not the best ANC because there’s no computing. But having individual amps allows the headphones to have better individual volume control, and you don’t have to hear every time someone jacks in, or low volume issues is too many people are jacked in.
My guess is that the seat checks for continuity between the two ground sleeves. If the grounds are connected, then it's the airline headset and it can operate in the two-pin noise cancelling mode. If they're not, then it'll operate in standard stereo-out for each port independently. Really quite clever, I think.
@@1337GameDev The "modes" can be very simple. Possibly even implemented in hardware right in the seat itself. We know it's not just "always mono" because they're stereo if you plug in normal headphones. Detecting the common ground could be as simple as a tiny detection circuit which drives solid-state relays to swap the audio paths around. And feeding mic audio back into the speaker (inverted) is easy enough to do too... if you don't care too much about the quality. Whole thing could be on a nickel-sized board that costs all of $0.25 per seat and needs no active logic components whatsoever.
more likely that both pins are wired stereo which is why his normal headphones worked and why the special headphones didn't seem to noise cancel very well
The old pneumatic headphones were wild. I was on a few flights that had them as a kid in the '80s, and it was funny how you could cut off the sound just by kinking the "cord" like a hose (because it essentially was a hose). Also, one of those flights with those weird headphones was my introduction to "Don't Buy the Liverwurst" by Allan Sherman, so that was cool lol.
I actually used those once as well, way back when I was a kid. The plane I was on was definitely an older model at the time too. But finding out that I could hear the sound by turning up the volume and putting my ear near the hole where the tube plugged in was wild.
They used to charge $2.50 for the use of those pneumatic headphones in the 1970's, which was a fair amount of money. It did occur to me that if I made away with one on one occasion, I could use them again and thus watch the movie for free thereafter. I don't remember if I ever did, though.
Another "advantage" to off-board cancellation is that the airplane staff can shut it off on their end when they make announcements or need your full attention in an emergency
Yeah, pretty much every airline has been using them for decades, it's an industry-wide de facto standard that dates back from the early days of stereo headphones. Noise cancelling is a recent development, and so is the inclusion of regular TRS jacks by some airlines to allow people to use their own headphones.
I'm very doubtful. If the noise cancelling happens externally, Every chair would have to be wired separately. In a 737 with 100 passengers, the receiving computer would have to have 400 connectors. Just the mechanics of it sounds implausible.
@@rasmis They are already wired separately. The in-flight entertainment system for each seat is independent from the other seats - each passenger can choose what they want to watch separately. The noise cancellation circuitry will be part of the IFE computer for each seat.
@@rasmis Is it really so hard to believe? (fyi just chiming in friendly here, not trying to fight over it I promise). Hardware accelerated audio/video encoding is not expensive in the slightest with todays standards and technology. Planes fly with multiple redundant computers, and they also off-load a lot of the entertainment to DirecTV depending on the airline. Satellite TV gets picked up by the plane and each chair has its own little equivalent satellite TV receiver (think the little DirecTV boxes each household member gets for themselves that talks to the master receiver, same thing) with the remaining local entertainment functionality managed by an entertainment system/computer specially designed for such purpose. You can get incredible noise cancellation packaged in tiny little earbuds honestly, so having each chair wired up to a master entertainment system really isn't that crazy. I work in IT for an MSP500 company. You'd be surprised how many people you can cram into a piece of shit server from 10 years ago with the right configuration hehe I would like to point out though that a few decades ago you would've been correct. Inflight entertainment systems used to be shared, you watched the same movie as everyone else and were lucky to have a dedicated screen for it infront of you at that. Now-a-days however this is very trivial (by relative comparison. obviously this shit is complex inherently) and pretty much every airline his some form of independent inflight entertainment per-seat now.
What airline are you guys flying? I've flown quite bit over the last couple of decades and not once have I ever seen this connector. Granted, I fly economy and obviously it's different in other classes (like Delta Premium shown in this video).
It looks like the plug isn't keyed to being inserted in a specific orientation, so it makes sense that there would be additional circuitry on the plane to detect what was inserted: it would need to detect which ground pin belonged to which circuit.
@TheJQuon Oh, I got the pinout wrong. I thought it had L/R audio on one side and noise cancelling on the other side. But no, it's one side audio and one side noise cancelling on each and then one side has ground for both speaker and the other has ground for both noise cancelling mics. So yeah, you're right. It would just reverse the channels and change which ground pins are connected. Still, I'd imagine those to be keyed. Anyways, there's even a three prong TS connector on some airplanes, which seems to be left audio on one + ground, right audio + ground on another and mic + ground on the third. This one seems to be keyed, though.
When I flew in the 80s it was the same plug, but the headphones were extremely simple and had absolutely no noise cancellation. It is possible that there were not as many connections per pin, but at least there were two pins. So, I don't think noise cancellation is the reason it looks the way it does, even though they use the two pins today for noise cancellation.
You are exactly right. Noise cancellation was not the original reason for the double plug, it was to help prevent theft. It worked too, because no one ever bothered to take them from the planes due to the plug difference..
some of those were mono, one channel per prong. It was like that for a long time, without any noise cancellation feature. there would still be audio coming out on both side of your headphones, just both side would be the same since it is just mono.
I am amazed that you thought that headphones were just available to take away. I’ve been flying since before you were born and the headphones were never a gift item for you to take away.
I'm not sure this really answers why they have the two-prong connector: the ANC is a very new development and the older headphones still used two prongs when the extra conductors weren't necessary. I find the theft / redundancy / durability answers much more likely as the original reason and these headphones are just adding the extra ring connections to the same plug for the sake of backwards compatibility (we still use aircraft first developed in the 70s). Back then, replacing headphones would have been even more expensive so deterring theft sounds like a very valid reason. I'd also suggest that the extra prong helps reduce how much the plug can move if yanked by a passenger. Therefore the connector in the seat (which isn't too easy to replace) is less easily damaged.
The real answer is that there are two reasons for the two prongs. The original two-prong plugs are, indeed, to make it so people don't take the headphones (and, alternatively, to make it so people have to rent headphones from the airlines but adapters made short work of that). Airlines tend to now give you throwaway headphones in economy (if any at all) that are much cheaper to produce instead, and those will usually just have a normal 3.5mm jack like everything else. The plugs in the video are for noise cancellation for the business/first class headphones as stated, while being backward compatible with the earlier two-prong plugs and normal 3.5mm plugs. There exist alternative versions of this plug as well. One uses the normal two-prong (dual mono, TS) plug for audio and a second 2.5mm prong (TRS) for the ANC, arranged in a triangle. And more recently, a version of that 3-prong plug that actually replaces the prong with flat contacts, pogo-pins on the jack and magnets to hold it all together. This to help stop people from breaking the jacks.
3:40 ... also this way they can control the noise cancelling from the plane. So it can be disabled during the safety briefing or whenever there's an emergency.
I remember using pneumatic headphones back in the 1980s, I still remember how the music on the inflight entertainment system used to pause when an announcement by the cabin crew was being made. Do these have a similar feature?
I remember as a kid flying with Qantas, and they used the pneumatic headphones up until around 2000. I remember because my dad taught me a prank where you unplug your neighbour's headphones then blow into the plug, and being disappointed when the electronic ones came out.
0:10 "you can not keep the large headphones". This isn't actually a universal truth, and varies between airlines. My approach is to assume that I can not keep them, but if the packaging that they come in says otherwise, then it's game on.
Good video! One thing I'd like to point out is that the processing of the active noise canceling signal is most likely done in an analog fashion. you only need to amplify the signal and then invert it which to can do with 1 or 2 opamps which are dirt cheap. Doing it digitally would be way more difficult and expensive.
Pro "just the" tip: if you sort of half-insert your regular 3.5mm into these your earphones will work as normal. On some planes when you go all the way in, the sound cuts off on one side (by design, I'm guessing)
I suppose another benefit of having the in-flight entertainment system handle the noise cancellation is so that they don't need to worry about batteries either, since (IIRC) active noise-cancelling headphones need power to do the noise cancellation.
hey, remember that "file types that are actually .zip files"? can you make a part 2 for files like sb, sb2, sb3, (those are for scratch, a kids programming language made by the Massachusetts Institute of Technology btw) and more file types that are just zip files or like zip files?
Not to mention the older plane headphones which are even weirder as they are just plastic tubes with no driver at the end, or even any electronic components at all.
It's been a while since I've been on a plane with any kind of headphones jack at all. Normally you bring your phone, your headphones and connect to the plane's wifi to access whatever limited stuff they have. I remember those jacks from the 90s. They stuck around until this decade.
That one is new to me. Latelly I could just plug my stereo headphones on the top plug at the arm-prest and it would work in stereo just fine. But WAY back in time, like, 2009, I did receive some of those cheap phones witht those double plugs, and both were mono, having only the tip and the ground, no microphone feedback for noise cancelling at all. That feature is completly new for me 😁
I too have never seen the microphone opening in the headset. For a proper cancellation, you need independent microphones for each ear because the signal comes at different times (or phase).
This connection goes way, way back; and I believe it is for noise reduction not noise cancellation. I know this dual plug connector has been around since the early 70's at least (I remember seeing them as a kid, and some audio gear we had actually had "airplane adaptors" for just this thing). Likely it isn't doing noise cancellation at all and doesn't have any microphone. Rather, it is a balanced signal (L+, L-, GND; R+, R-, GND). The advantage of this is that it cancels out common-mode noise. So aircraft electronic noise that gets picked up by the wiring to the jack and up to the headphone get cancelled out as the same noise is present on the + and - polarities of the signal and is thus easy to filter. With just a simple extra bit of circuitry, it can be built to detect when only one jack is plugged in and switch the pinout to L/R/GND, allowing unbalanced audio to a standard headphone set. This would be an update to the original design which I believe used just TR (mono) plugs, one for left, one for right, unbalanced. Adapters came with compact cassette decks for a while that converted that setup to a TRS stereo headphone jack.
This is just left over from the early days of having a few monitors over the aisle for showing movies. If you wanted to hear the audio you had to rent their ‘special’ headphones or earbuds, which were collected before landing so you would have to pay again on the next flight. Planes are incredibly high tech, airline senior management not so much! Some have made the massive leap to a single jack stereo, so only a couple of generations behind now.
On a Qantas flight I took once it was back when they were one use disposables, so you could take them with you if you wanted. Yeah, I did for the same reason, the novelty connector and as a kind of souvenir. The hostess actually gave me a couple more pairs that other passengers had discarded!
I was on a Qantas long-haul flight this summer, returning to the US from Australia, and they were still handing out these cheap disposable headphones to people who wanted them. I took a pair and found out they were actually just normal earbuds connected to an adapter. Feeling clever, I detached the adapter and plugged in my own headphones. It worked well. I was even able to reuse the doodad later on a US domestic flight, but I seem to have misplaced it recently.
All it would take to do noise cancelling in that setup is for them to invert the phase of whatever the mics are hearing and mix it with the program. Inverting the phase of an audio signal is basically the same thing as swapping the red and black wires on a speaker. It's something that wouldn't even require a microchip; it could be done with discrete components alone.
All the reasons you've listed are probably correct, but, I know that one of the major reasons is so that they (the plane) can control the audio -- this is the reason why you can still hear the official announcements even while wearing (apparently) active noise cancelling headphones...they can control what sound to 'pipe' over & above the audio you're listening to -- esp. useful in emergencies as well as for many types of announcements.
Why couldn't they intercept the audio stream of a normal jack? That seems to be more a function of what they're plugged into than of the headphones or interface itself.
@@reidprichard Hmmm...Interesting point. Maybe the internal electronics are different? I'm afraid I'm not qualified or knowledgeable enough to answer that legit query. Sorry...
You wouldn't need more contacts for that. Until very recently, those used to simply be two mono jacks side-by-side, and yet the in-flight entertainment system already had that functionality.
Maybe you're too young to remember, but this was the standard before seat back entertainment systems. The noise cancelling is new, though...they definitely just had one channel per prong, at least in economy. I still have adaptors for these plugs, but not every airline uses the same spacing.
I thought they would have been a small version of XLR where you get + signal, - signal, and ground. The idea being that you take the difference of the signals and the EM noise would get cancelled while the signal get amplified.
Far more along the lines of what I was thinking too - given the amount of high voltage circuitry and transformers so tightly packed into aircraft I wouldn't be surprised if there may have been some resonant buzz which could be cancelled, similar to a balanced cable.
Emirates have this plus an extra plug making 3 prongs, the extra one is a power supply for the sound cancelling feature which is very good. Plug in, switch on and turn the volume to zero and all the background noise disappears, plus they are totally useless if you steal them as they will not fit anything else.
Qatar uses the 3 prong system, too. I was wondering what the third prong was for, but I didn't want to plug anything into it just in case it was powered, and I fried my $300 Bose headphones. It sounds like I made a good call. :(
Moving the noise cancellation computing to something outside the headphones also means that they don't need to provide power or charging via the jack. No need to have hundreds of potentially dangerous Li-Ion batteries all over the plane that are constantly getting charged and discharged.
Noise cancelation is surely out of phase if the signal needs to go from the headset to th computer in the seat and then back to the speakers. That delay messes up the noise canceling feature. And that's assiming they are designed the way you described it.
Qantas has these, and so far all the other airlines I've flown on both here (Australia) and overseas that had headphone jacks had the normal single jack that you could plug your own headphones into. And I thought Qantas was the only airline that had these dual jacks. Thanks for clearing that up.
Interestingly enough regarding this is that Qantas actually changed the adapter on the headphones from the hardwired dual-prong set up on the headphones to single jack with an adapter, so you _can_ more easily use other headphones.
The point about plugging in one prong and the audio still works for both ears - is it because both holes actually play stereo audio so people can plug in the 2 prong headphones whichever way and still have the stereo audio
I think the propagation delay of the signal would not be in the perfect phase, and why it didn't work that well. Time it take to reach the computer, get processed and sent back. I think it would be more successful if they just focused on canceling the engine noise with central cabin microphones placed in zones (ignoring people noise),and process a noise cancellation signal for the passengers in that section and apply that to the audio signal in that section.
This is very unlikely. delay of propagation and treatement are way lower than any perceptible human one. after all the highest freq is 20kHz. 50 microsecond is an eternity for sound processing.
@@tatoute1 Just a quick note, it needs to be significantly less than 50 microseconds, maybe 5 uS or less. But not that big an issue, ANC is primarily required upto 5kHz, after which passive noise cancelling works pretty well.
Given electricity travels at lightspeed I wouldn't have thought that little cable would add much in the way of propagation delay vs processing on-chip inside the headphones :p
I strongly question the idea of using a computer to do that. All one needs to do is to invert the microphone signal in amplitude and mix it in into the audio signal. This can be done in the simplest case just with the wiring. The most complex technical system I would expect would be a simple inverting amplifier, realized with a cheap OpAmp, which is only used because the microphone would need some power by itself and thus one needs to bring a powerline to the seat anyways. No need to throw a computer at it, even if µC are really cheap these days. It just would complicate the whole system by the need of A/D conversion of the audio and microphone signal, mixing them together and have them D/A converted for the headphone. Much to complicated for something which can be done much simpler with good old analog electronics. The secret behind noise cancelation is in the placement of the microphone, which must be as close as possible to the ear.
@@kallewirsch2263 lol it's not that simple. Everyone would be doing that if it was like that, and ANC headphones wouldn't cost what they cost now. If you simply do what you said, it will 1) also filter out the audio and 2) still not work because to cancel out, the signal needs to exactly match up.
this would be a really cool way for some headphones to support balanced audio, have 2 mono jacks with 2 prongs, but of course a 4 prong different sized plug is what actually ended up being used.
They do. You can buy them from several manufacturers. They're just not that popular. Your configuration is wrong, though. For balanced operation, each channel needs 3 conductors. 2 for signal and 1 for ground. Also, its not the connectors that make something mono or stereo, its the recording. A 2 channel audio system for stereo music will have 2 identical or mono channels. What makes stereo its own format is how the 2 channels are recorded. On playback, the stereo signal goes to 2 mono channels.
@@AT-wl9yq The definition of a balanced signal is that it doesn't use ground, it uses a pair of conductors - two - in which a dedicated return conductor carries (only) the same current as the other conductor in the pair. Two conductors - signal A and signal B. See for example CAT5 and CAT6. Those are balanced signals, so there's no ground. If the signal wires are neither twisted nor coaxial, the balanced signal wires may be covered by a SHIELD. That shield may be sheet metal on a PCB, may be a braid, etc - it's not connected to the signal, if it exists, and is not part of a balanced signal channel. If there is a shield, it may or may not be connected to a resistor, a capacitor, or both. Those resistors and/or capacitors may or may not be connected to drain to chassis ground. In any event, if the shield exists, it exists to protect the two conductor signal. It isn't part of the signal.
@@senseisecurityschool9337 Balanced headphones sound like a total gimmick. There is no need to reject noise at headphone level signals, what kind of interference is going to penetrate that strength of signal to any noticeable effect?
Proprietary connection means they can control who can access it. In coach they often make you pay extra to use them. If they accepted standard connections they couldn't demand money for renting them.
Those are most likely balanced headphones. Balanced operation would make sense because its a much better way to transfer an audio signal when you need to use long runs of cable. Every seat on the plane has to be wired for audio. That's a tremendous amount of cable, as opposed to what you would have on a personal system. Also, there is a "noise cancelling" aspect to balanced operation, but it works a different way, and achieves a different result than what most people think noise cancelling is. For balanced operation you need more conductors than a typical single ended design. If you look at the connectors on the airplane headphones, you'll see that they are a TRS design. The 2 rings break the connector up into 3 zones. Each zone is a conductor. (For balanced operation, any 3 conductor connection will do. XLR is also a popular choice.). On regular headphones, you have a signal and a ground, + and -. On balanced headphones, you have 2 signals and a ground, + + -. The 2 signal conductors carry the same audio signal, except that they're the opposite polarity. This is for noise reduction, not noise cancellation. There's a difference. Noise cancellation is done so you don't hear noise around you when you are using the headphones. Balanced circuits deal with things that effect the signal going through the wire itself, not external acoustic noise. You can buy balanced headphones, but they're just not that popular. The headphones themselves will have 2 connectors like the ones in the video, and your headphone amp will have 2 inputs. The only difference between the airplane headphones and balanced consumer headphones, it the connector itself. The ones for the plane use 2 trs mini jacks, and the ones sold to consumers use either 2 full size 1/4 inch trs jacks, or xlr. It doesn't really matter because electrically, they are all identical.
I think you're right. A balanced line makes a lot of sense in airplanes, even more if you consider everything runs on AC at 400 Hz. The whining of the 400 Hz in some planes is very noticeable when the crew uses the PA system, imagine having that tone the whole trip well inside your ears!
This seems the best explanation to me. I just so happen to work with these systems on this airline so if I remember I’ll go digging through some documents and see if I can find out if it is the truth
Out of 700 replies, you are right on the money for explaining balanced analog audio over long cable run. The noise cancelation is in the context of reducing electrical noise or interference, not in the context of reducing acoustic noise offered by active noise canceling headphone such as Bose QuietComfort. On newer airliners that have individual entertainment panels, each panel provides amplification for the headphone with a much shorter cable run, thus unbalanced stereo TRS 3.5mm jack.
Balanced transmission (which are just differential pairs) are not the same as balanced headphones. When headphones are "balanced" it means they do not share a ground, each channel gets its own negative going back to the amp that made the signal. This helps eliminates crosstalk between the channels but does little else to suppress noise. Noise suppression isn't really needed in headphone signal lines because of the impedance most headphones operate at. Your typical bookshelf speaker operates at around 4 ohms, while the lowest you'll typically see headphones' impedance is 8 ohms (in the really cheap ones). My over the ear headphones have 300 ohms of impedance while my in-ear's have about 26 ohms of impedence.
@@roberttseng6147 Except they aren't because Joe literally showed the schematic for the headphones and it shows the signal paths go to microphones, lol. Did people even watch the video? Wtf.
The last plane I was on, they used one of these two-jack setups, but their provided headphones used a standard single 3.5mm jack to plug into a two-jack adaptor. So I could easily unplug the provided headphones (which were next to useless anyway) from the two-jack adaptor, plug my own headphones into it, and then plug the adaptor into the plane's sockets, and it worked perfectly fine.
I actually asked about this on a flight and the attendant said it's so the plane can feed emergency info right into your headset if necessary. He never said anything about noise cancellation.
The last time I boarded a plane, I got a dongle that converted a 3.5mm stereo jack into a dual-3.5mm jack. I kept it for a while for the novelty, but eventually “destructively dissembled” it.
I always thought it was just so you are forced to buy headphones from the airline instead of using your own. I'm surprised you flew on a plane with these jacks. Usually, I see everything just plugging into the infotainment screen in front of you now a days. I've not seen a plane with a collective movie screen in quite some time.
I'd be curious if the off-loaded noise cancelling might be designed to prevent the headphones from also canceling the "ambient noise" of cabin announcements.
On flights that I've been on, they just cut off whatever in-flight entertainment you're listening to and pipe the announcement directly into the headphones. it's part of why nowadays I just watch things from my phone instead of bothering with the in-flight stuff.
They used to be passive earphones with the speaker just behind the socket, two holes for two ears. Maybe when they went to an electric system it was so they didn't have to replace the aircraft seats with different ones with different holes punched in them?
This is actually a really interesting way to reduce the cost of the headphones so that you don't lose so much money when idiots like Joe take your headphones Also, I see an open source hardware project in somebody's future to build a microcontroller based system that will not only adapt these to normal 3 and 1/2 mm or maybe even Bluetooth but also provide the missing noise cancellation processing
I wonder if having the noise cancellation done on the plane rather than in the headphones would also allow announcements from the pilot/stewards to bypass/override the noise cancelling and be routed right into passenger headsets, for those who are distracted!?
The reason for that is that the airline used to sell you bad earplugs you couldn't use your own. the plug has been around for so long before sound cancellation the first time I flew in the 90s, so you had to pay to be able to listen to the movie they played on the plane
@travis1240 I flew internationally last month, the "premium" seats have this, the "economy" seats use regular phono Jack's and disposable ear buds passed out by the flight attendants. (The 14 hour leg was in a "premium" seat, the 4 hour domestic leg was in "economy," so I saw both.)
here I was thinking they were balanced mono to reduce RF interference... ( ground, + and - signals, where one gets flipped so they're either both + or both -, but since they both had the same interference BEFORE one was flipped, after the flip one now has inveted noise so adding them together cancels the noise out)
they override and pipe the announcements through the sound system, like travis said. this channel seems to have fostered an audience of people who just talk out of their asses.
My guess would be that the main reason for implementing noise cancellation like this would be so the headphones themselves don't need to be powered. If the active noise cancellation was done in the headphones themselves (like your consumer ones) they would need power. Either a lithium battery or externally provided power would come with risks that wouldn't suit use in an airliner cabin.
That might explain it now with contemporary ones, but planes have had a weird connector for their headphones for _decades,_ long before noise-cancellation (and back then, it was mono pins). Iirc, back in the 70s, they'd actually use one for the music/movie, and one for announcements.
The noise cancelling circuits would be part of or very near the socket in each seat as 1) the noise to be cancelled would be unique to each ear piece. 2) you'd want the minimum delay (distance) in generating and applying the inverse noise signal onto the output back to the relevant ear. 3) so you could isolate this extra cost to particular higher paying seats like first class or business class. Note - cabin broadcasts override all the airline entertainment audio signals so that you can still hear the broadcast on your own stand-alone noise cancelling haedphones
Checking if anything is plugged in into one or both jacks is really easy. The little spring contacts that make contact with the plug while plugged in do the trick. They are resting on a contact on the other side, and if you plug in your plug they get lifted from that contact. So all you need to do is so monitor that contact. Most times is done on the ground contact, so the computer checks if there is still ground potential on that contact, so no plug is plugged in.
Lol, I just saw your comment about it... There’s also another type of headphone plug with four segments just for the speakers it’s called a balanced output usually used on high end headphones
Two prong adapters are definitely not used specifically for noise cancelling, as they were in use before noise cancelling headphones existed. As well, most newer airplanes have switched to using the standard single 3.5mm port, which presumably would include any noise cancelling features that the airplane includes.
Yes, I have seen this elsewhere - it's used in Audiometric testing devices. I also have memories of an early 2000s Minidisc player with this on - maybe by SHARP?
Fascinating video! I've got a hypothesis to share. The microphones integrated into the headphones seem to be designed for capturing high-frequency noise only. Meanwhile, the low-frequency noise appears to be picked up from another source within the plane. Since low-frequency noise tends to be consistent across environments (similar to using a single subwoofer in home theaters but multiple speakers for higher frequencies), this approach not only makes the design more cost-effective but also explains why you hear some noise when you plugged in your own headphone.
low frequency has higher carry and penetration than high frequency, to better explain. this is why sirens modulate between two tones; a low one so you can hear it coming from far away, and a higher one so it is easier to tell what direction it is coming from as it approaches (low freq sounds can be heard farther, but are harder to locate source.)
It's a typical feature to detect when the jack is plugged in. In this case there is just a bit of logic that will properly multiplex all output signals to the one jack if the other isn't used.
You got me down the rabbit hole of two-prong airlane headphone jacks. I discovered that premium cabins and legacy airplanes have three-prong headphone jacks that do the same thing, except two jacks provide a left and right audio channel while the third offers power to the headphones. All of the extra prongs are for redundancy and discourage passengers from taking the headphones.
Thanks for the bit at the end. Im pretty sure I used a regular apple earphone when I travelled previously and plugged it into one of the ports and it worked fine.
I don't recall seeing the dual jack on any of my flights. I did assume it was related to the pneumatic headphones I remember in my younger days. The concept of central noise cancelation is intriguing, even if not effective. Thank you for this. Following now!
Another reason could be that with the audio processing happening in the plane's electronics, the headphones can be completely passive devices without needing batteries. If the active noise canceling was happening in the headphones they would need to be powered in some way.
An advantage of that setup is that the noise cancelling can easily not filter out announcements. It could even be set so that the voices of the flight attendants is given special treatment so that they can be heard. Regular noise cancelling headphones WILL filter out the voices of peoples around you along any actual noise present. Then, for using your own headphones... A simple switch in both sockets can do the job. Only a single socket is used ? Act like a regular audio socket.
I remember the headphones on planes having these back in the 90's, too. We were allowed to take our headphones, too. They just had a regular 3.5mm jack that was plugged into an adapter with the 2 jacks on it and you could take it off and use them normally. So, there goes that theory.
I suspect it also could have to do with grounding. Since planes are always electrified having a second pin could make sure the excess static would have a shorter path to ground rather than going through you crating a noise in the headset in the process.
I used to have headphones where the second prong could fold away for daily use and then you would just flip it out whenever you were on an airplane. It had noise cancellation, but it was really just a bunch of white noise LOL
I suspect that it is originally an anti-theft thing as I recall these from back in the day when they started with electronic headphones. I don't think audio-cancelling was even a thing back then? I think back then they were two mono plugs.
Its quite easy to detect, if there is a normal pair of headphones connected: there are 3.5mm jack's that includes switches, which are activated if something is plugged in. If only one of the two switches per socket is activated, it says to the computer to deliver Stereo sound to just this plug.
Also a single stereo 3.5mm jack is a lot easier to snap off when you get up out of your seat in very cramped conditions. That double jack is very solid.
This setup is so old I also got headphones with this connector way back in 2008 when I had my first transatlantic flight. Interestingly enough, those had a hinge on one of the prongs so it could be folded up when using with regular 3.5mm sockets.
electronically, it is VERY simple to see if there is connection between 2 electronic connections, and looking at the 2 prong pinout, there is connection between the prongs, so mic ground is on one prong and a mic output on the other and vice versa for the audio drivers, so it detecting a standard set of headphones might just be by reading continuity between the prongs
I took home a set of these from a qantas flight ages ago, and they had noise cancelation built in. In that setup, the extra connectors on the dual 3.5mm jacks were used to feed 18vdc to the headphones from the seat plug to power them up. Note at 4.10 the picture shows dual mono 3.5 jacks, not stereo ones. Must be yet another use case out there for those ones ….
most PCB mounted 1/8'' and 1/4'' TRS jacks have a pin that detects weather the plug is physically present in the jack, so all you have to do is assume that if only one of two jacks is connected, its a stereo headset and you should output audio on both channels. that is how I assume this works. that or detecting the different impedance between the plane headset or yours.
I think the big value of having the processing in the plane and not the headsets is because you don't need any power in the headset, i.e., no need to charge them.
looks a little like the Kenwood audio jack found in many handheld transceivers. However the Kenwood jack combines a 3.5mm and a 2.5mm with one being used to transmit and the other to receive.
I just looked and apparently you're not supposed to take the pillow or blanket either lol 💀💀
• Also I should clarify, this doesn't mean every headset using this double plug has noise cancellation. Delta just used the extra plug to make them both stereo to get extra channels to use for that. Other airlines might literally just use 2 mono plugs.
• Also I didn't state this explicitly but the microphones are inside the headphones next to the speakers. That's why there are channels for it on the plug, so the noise signal can be sent to the computer to be processed.
(By the way I did not actually take the pillow and blanket home. I just assumed you could because the blanket felt so remarkably crappy and cheap that I assumed it was disposable, then extrapolated for the rest of the items ¯\_(ツ)_/¯ . And the only reason I took the headphones was because I wanted to make a video about the plug lol. )
Is Delta okay with you taking the headphones home lol
@@chiroyce If you mean those no-branded one you get in coach/economy class, they are so mass produced that most airlines won’t care if you take them. Now, for branded ones made by Bose or Sony you get in Business/first class, that’s a different story altogether.
@@chiroyce I didn't ask
But taking the under seat floatation device is cool because Delta wants to keep their customers safe even when they are not flying in Delta airplanes.
I got some noise cancelling ars technica headphones like 10 years ago that came with this adapter... and I never even thought to look up what it's for.
The noise cancelling version is very recent. The old design was two mono plugs for the L and R channels, and all the adapters you can buy are dual mono. As to the reasons? It really was to prevent headphone theft and provide a revenue stream for headphone rentals. It was also an adaptation of the much older dual-prong tube headphones where the speakers were in the seats, and the sound transmitted via rubber tubes.
>the speakers were in the seats, and the sound transmitted via rubber tubes.
Now that would be a more interesting video
@@frostedbutts4340I had those in an mri and they were god awful
And the switch to using the dual mono electrical setup started in the 80s, before noise cancelling headphones were a thing.
Came to the comments to say everything you already said. Excellent breakdown!
I used to work as a technician for Bose, many years ago, on their military noise cancelling headphones. The noise cancellation doesn't work well in these airline headphones because the microphones, being mounted away from the headphones, aren't picking up the ambient noise anywhere near your ears.
Noise cancellation works by picking up the ambient noise entering your ears from outside of the headphones. Then it inverts the signal and mixes it with the headphone audio, thus, cancelling out the noise, but not the audio you want to hear. The amplitude, frequency, and phasing must be accurate for effective noise cancellation, and the best way to do that is to have the microphones as close to the ear as possible. Hard to explain, but I hope you get the jist of it.
Doesn't that create a problem of mics picking up audio from the headphones themselves (unless there's proper isolation over the ears)?
@@masterman1502 I would think that you could remove that sound from the microphone noise, as you have the original sound via the line.
@@masterman1502 why would you have noise cancelling headphones that aren't closed to begin with? First cancel as much as you can acoustically, then add active noise cancelling.
@@henrihellyou're in for a surprise then, as good headphones with ANC have both external AND internal microphones to work their magic with!
@@phaelox never doubted that. Though their probably still closed headphones. The only reason you'd want open headphones anyway is specifically so you'll hear something from outside.
Maybe in newer or updated planes these might be for noise cancelling, but when I use to fly between 2000-2012 it was so you'd buy the headphones airlines had for $5. They most certainly didn't have noise cancelling features as they were the most basic headphones with no padding much less over the ear design. Instead I bought a pair of 3.5mm adapters to convert the 2-prong plug to a single 3.5mm jack which allowed personal headphones to get both audio channels.
They were free on Air Canada and I have a pile of them. Need some? 🙂
Yep, they wanted a way to grab more money from you with cheap, mass-produced off-the-shelf products. 2 mono 3.5mm jacks was the perfect solution. Now it's just the airline standard.
I also bought one of these adapter ahead of flight. And that was 2017 with ThaiAirways on their older 747. Served me well.
@@frostbite1991 it’s more that they started charging for something they used to give away, those plugs and headphones go back way farther than 2000. I remember listening to the ATC feed and bad music on these in the 90s.
You had flying time machine??!!
i used to be a aircraft electrician the left one is for the in flight intertainment system and the right is for the public adress system (PAS)
ancouncements from PA system
@@AchieScottGraham I was just thinking when watching this, couldn’t be as simple as a way for them to send announcements to all the headphones regardless of what they are watching or listening to.
@@Olbaidon It's not. Since the audio you're listening to in this scenario is also controlled by the plane, they can absolutely just mix it in over the regular audio on the same channels, and/or pause the media. No need to run multiple source lines and do relatively expensive analog audio mixing on-device. They used to just be dual mono jacks (and still are, in other planes), which is why these headphones are broken out with one speaker and one mic on each side, rather than one input side and one output side, or, as was suggested, two separate audio sources.
They also could turn off the noise cancelling whilst announcements are being made (though they could pipe this over the audio circuit anyway).
Or in the event of an incident, where cabin crew may be shouting instructions.
That's how they do it already, they interrupt what you're hearing through the headphones with their announcements. Pisses me off when I'm trying to watch a movie and they're busy thanking frequent fliers.
I am on the team that design those airplane headphone sockets.
You are correct on almost all counts!
The design of the plug is to minimise "pilfering" (theft) of the headphones.
The connector format on the headphone and socket is described in the ARINC 628 standard. The plug you have there is a ARINC 628 - D2 plug.
The noise cancellation actually happens in a small circuit inside the socket. So the microphone signal does not travel all the way to the IFE unit.
When audio works on normal headphones this is a feature on some of the sockets. They they can detect that a normal headphone is plugged in and put an audio signal on the socket rather than use the signal for the noise cancelling.
In the case of that socket you used on the plane I'm almost certain it is an IFPL brand socket which can have the sockets changed when they wear out too.
Interesting to see you cover a topic I know very well.
So can one use a "normal" headphone (or a wireless bluetooth with noise cancellation one with a wireless adaptor) by plugging it into ONLY ONE of the 3,5 jacks?
@@axios101 yes many sockets support signal switching
But be aware that not all of them do.
@@ExarchNZ in that case i use the old trick of not inserting the whole thing but leave it halfway. Sure its mono, but at least you get both speakers and not one...
@@freeculture That works because you are connecting the R driver of your headset to the connector sleeve, which is normally a common GND inside the socket. The audio is referenced to this GND.
So its like having the two drivers in series with each other sort of, which is also why it sounds quieter than normal when you do that.
I guess in a pinch its better than nothing!
This design removes the need for more logic in the headphones, and probably also the need for a battery to drive the logic! Not sure an audio signal has enough power to supply logic circuits..
0:16 Delta wants to:
Know your location 📍 Lol
I got an airline adaptor for free with my Bose QuietComforts years ago, so I was aware that this was a thing. I've never used it though - the only time I've ever flown in a plane with in-flight entertainment (British Airways A380) they'd already transitioned to standard single-jack arrangements! I did bring it just in case though.
Agree
Interesting, I was on a British Airways flight to boston in a A380 in April. They still had the two-pronged plugs there. That was Economy+ tho, maybe they haven't phased it out for the masses or it depends on the individual planes.
My adapter is still in the slot in the case. I've taken loads of flights but never had to use it!
@@arachn01d Ive occasionally used my adaptor on my old QuietComfort 15's. I've never had decent noise cancelling headphones in business class. I have in first but my own are still superior even to these. Always use your own high quality headphones for superior audio and hygiene.
@@normangoldstuck8107 always use my own headphones. Just never needed an adaptor on either virgin or BA.
Riding an airplane to Hawaii in the early '80s, the headphones did not use wires. Instead, the sound would travel through the air in rubber tubes to your ears.
Pneumatic headphones
I remember those things. It was a rather short-lived technology that didn't catch on with most airlines. Not sure who was selling it.
I remember it in the 90s too
@@nolongeramused8135 I don’t think it was that short lived. I’m 61 years old and I’ve flown several times a year since I was little kid and those tube style headphones were around until sometime in the 80s, or even later.
Still used in MRI machines, personally I find the sound quality is usually poor but it's a cool use of the technology.
I really think the noise cancelling aspect has been a more recent development that has just taken advantage of the existing hardware. Sometime around the year 2000, Qantas switched from the pneumatic headphones to the 3.5mm jack with the dual pins. There's no way they were running an active noise cancelling computer for all the passengers 24 years ago. The idea of making them incompatible with most people's personal electronics makes a lot of sense. Especially 20-25 years ago, it would be silly not to pinch a pair of headphones at the end of your flight if it worked with your walkman/discman/Personal computer
I agree. These double connectors were around long before there were affordable noise cancelling headsets. Airlines wouldn’t spend the extra money if they didn’t have to. They might have added noise cancelling later (for first class passengers) but they didn’t start that way.
I have no idea IF, but noise cancellation is actually much simpler than you might imagine
It does not need computers or other high-tech
What it needs is a simple audio amplifier with all required attenuation to invert the phase of the incoming signal. Airlines could easily afford it since at least the 70s if they wanted, the device itself was affordable as soon as transistor amplifiers became commercially viable (although perhaps at not enough quality), but the idea of active noise cancellation itself didn't pick up until much later.
@@jwhite5008 with that in mind, it would make sense that they had a centralised noise cancelling feature that worked to remove engine noise. They can get loud, and the only way to give people a somewhat decent audio experience in that case is to try to minimize the engine noise. Also, by focusing on specific noises of the plane it probably makes the process a lot easier.
Some are just two 3.5mm jacks.. That are just 3.5mm jacks.
Some are and have been two mono plugs, for decades.
Seems plausible to me, that's the only way the pinout makes any sense to me. If you were designing this today and somehow thought two 3.5mm Jacks where the way to go, you would absolutely make one of the jacks use the normal TRS Left - Right - Ground pinout, and the other one Left Mic - Right Mic - Mic Ground. Then the headphone socket would be compatible with any old pair of headphones that the passengers bring on board. It probably wouldn't even need any extra consideration in the noise canceling module, since no mic signal should mean no cancellation signal is generated to mess with the audio.
But if this was originally meant specifically to be incompatible, then this current iteration would just use the existing pinout, to be compatible with that old variant on existing planes, even if they don't use the noise canceling.
There is no additional processing. If you open a 3.5mm jack you will likely find switches. It is very easy to wire them in an arrangement making the mic line an actual output. Also some driver chips can probe impedance and/or voltage on line (mic is typically biased) so switching can be done just by toggling two MOSFETs.
Yeah I don't get what he meant by processing. It's just inverting the sound. No processing needed.
@@Liggliluff inverting the sound is also a process xD
@@Liggliluff apparently there is a bit more than that going on in active from what i've heard - a bit of digital delay or some other kind of DSP to account for the distance between drivers and your eardrums, among other things. "How Noise-Canceling Headphones Create Silence in Microseconds | WSJ Tech Behind " is a decent video explainer.
@@Liggliluff It's not that easy because the microphone signal is extremely weak. At a minimum you would need to amplify that signal by an amount dictated by the speakers that were connected. There is absolutely audio processing going on in ANC.
There’s no computer it goes to. Each chair has a tiny headphone amplifier/signal inverter. You have to think as cheap as possible. The microphone signal is inverted and combined with the incoming audio before being amplified. It’s not the best ANC because there’s no computing. But having individual amps allows the headphones to have better individual volume control, and you don’t have to hear every time someone jacks in, or low volume issues is too many people are jacked in.
My guess is that the seat checks for continuity between the two ground sleeves. If the grounds are connected, then it's the airline headset and it can operate in the two-pin noise cancelling mode. If they're not, then it'll operate in standard stereo-out for each port independently. Really quite clever, I think.
@@1337GameDev The "modes" can be very simple. Possibly even implemented in hardware right in the seat itself.
We know it's not just "always mono" because they're stereo if you plug in normal headphones. Detecting the common ground could be as simple as a tiny detection circuit which drives solid-state relays to swap the audio paths around. And feeding mic audio back into the speaker (inverted) is easy enough to do too... if you don't care too much about the quality.
Whole thing could be on a nickel-sized board that costs all of $0.25 per seat and needs no active logic components whatsoever.
more likely that both pins are wired stereo which is why his normal headphones worked and why the special headphones didn't seem to noise cancel very well
The old pneumatic headphones were wild. I was on a few flights that had them as a kid in the '80s, and it was funny how you could cut off the sound just by kinking the "cord" like a hose (because it essentially was a hose). Also, one of those flights with those weird headphones was my introduction to "Don't Buy the Liverwurst" by Allan Sherman, so that was cool lol.
Yes! As a kid I always wondered how those worked. 😬
My first plane flight as a kid had those crazy headphones. I always remember it as being hilarious
The hospital in our city still uses this type of headphones for patients in the MRI scanner. Perfect as they don't contain any electronics/metal.
I actually used those once as well, way back when I was a kid. The plane I was on was definitely an older model at the time too. But finding out that I could hear the sound by turning up the volume and putting my ear near the hole where the tube plugged in was wild.
They used to charge $2.50 for the use of those pneumatic headphones in the 1970's, which was a fair amount of money. It did occur to me that if I made away with one on one occasion, I could use them again and thus watch the movie for free thereafter. I don't remember if I ever did, though.
Another "advantage" to off-board cancellation is that the airplane staff can shut it off on their end when they make announcements or need your full attention in an emergency
The "processing" to detect if only one plug is used is literally just a switch in the socket that rewires the outputs
And the "processing" of noise cancelling is just inverting the audio. He likes the word processing, like those who like the word algorithms.
🤓
@@HeylonNHPThat emoji was the unicode consortium's biggest mistake. It's only ever used to harass people for... knowing things?
@@antonliakhovitch8306 i object to the use of the word harassment but otherwise agree.
Not on all of them! On the cheaper sockets yes, mechanal switching. On the fancier ones it's electrical, not digital... But not mechanical either.
I think most airlines use these weird two pronged connectors. I thought they were something to do with noise cancelling, it’s cool to find out more!
Yeah, pretty much every airline has been using them for decades, it's an industry-wide de facto standard that dates back from the early days of stereo headphones. Noise cancelling is a recent development, and so is the inclusion of regular TRS jacks by some airlines to allow people to use their own headphones.
I'm very doubtful. If the noise cancelling happens externally, Every chair would have to be wired separately. In a 737 with 100 passengers, the receiving computer would have to have 400 connectors. Just the mechanics of it sounds implausible.
@@rasmis They are already wired separately. The in-flight entertainment system for each seat is independent from the other seats - each passenger can choose what they want to watch separately. The noise cancellation circuitry will be part of the IFE computer for each seat.
@@rasmis Is it really so hard to believe? (fyi just chiming in friendly here, not trying to fight over it I promise). Hardware accelerated audio/video encoding is not expensive in the slightest with todays standards and technology. Planes fly with multiple redundant computers, and they also off-load a lot of the entertainment to DirecTV depending on the airline. Satellite TV gets picked up by the plane and each chair has its own little equivalent satellite TV receiver (think the little DirecTV boxes each household member gets for themselves that talks to the master receiver, same thing) with the remaining local entertainment functionality managed by an entertainment system/computer specially designed for such purpose. You can get incredible noise cancellation packaged in tiny little earbuds honestly, so having each chair wired up to a master entertainment system really isn't that crazy. I work in IT for an MSP500 company. You'd be surprised how many people you can cram into a piece of shit server from 10 years ago with the right configuration hehe
I would like to point out though that a few decades ago you would've been correct. Inflight entertainment systems used to be shared, you watched the same movie as everyone else and were lucky to have a dedicated screen for it infront of you at that. Now-a-days however this is very trivial (by relative comparison. obviously this shit is complex inherently) and pretty much every airline his some form of independent inflight entertainment per-seat now.
What airline are you guys flying? I've flown quite bit over the last couple of decades and not once have I ever seen this connector. Granted, I fly economy and obviously it's different in other classes (like Delta Premium shown in this video).
It looks like the plug isn't keyed to being inserted in a specific orientation, so it makes sense that there would be additional circuitry on the plane to detect what was inserted: it would need to detect which ground pin belonged to which circuit.
Yeah, weird, that it's not keyed.
Since we are talking common / ground I suspect in the arm rest that they are connected together
I think you give them too much credit, they probably don't do any checking and if you insert them backwards the channels just get reversed.
Agreed. There's almost certainly no "sensing" going on. Why would it be keyed? If, uh oh! You reverse the left and right? Wgaf?
@TheJQuon Oh, I got the pinout wrong. I thought it had L/R audio on one side and noise cancelling on the other side.
But no, it's one side audio and one side noise cancelling on each and then one side has ground for both speaker and the other has ground for both noise cancelling mics.
So yeah, you're right. It would just reverse the channels and change which ground pins are connected.
Still, I'd imagine those to be keyed.
Anyways, there's even a three prong TS connector on some airplanes, which seems to be left audio on one + ground, right audio + ground on another and mic + ground on the third. This one seems to be keyed, though.
When I flew in the 80s it was the same plug, but the headphones were extremely simple and had absolutely no noise cancellation. It is possible that there were not as many connections per pin, but at least there were two pins. So, I don't think noise cancellation is the reason it looks the way it does, even though they use the two pins today for noise cancellation.
You are exactly right. Noise cancellation was not the original reason for the double plug, it was to help prevent theft. It worked too, because no one ever bothered to take them from the planes due to the plug difference..
@@cd7071 it also gave airlines the opportunity to charge for headphones. the airline business model loves nickel and diming people.
In the late 70s, the headphones were basically hollow pipes. They used to charge for that and you had only one channel.
Cool that you've done this.
Here in the UK, Poundland used to sell the adapters. The second two adapters shown are not suitable.
Stereo plug is called TRS, and stereo with mono microphone is TRRS. What they need is TRRRS, which might not be compatible with TRS and TRRS.
some of those were mono, one channel per prong. It was like that for a long time, without any noise cancellation feature.
there would still be audio coming out on both side of your headphones, just both side would be the same since it is just mono.
Yea I think Delta just uses the extra prong to their advantage for the noise cancellation
I am amazed that you thought that headphones were just available to take away. I’ve been flying since before you were born and the headphones were never a gift item for you to take away.
I'm not sure this really answers why they have the two-prong connector: the ANC is a very new development and the older headphones still used two prongs when the extra conductors weren't necessary.
I find the theft / redundancy / durability answers much more likely as the original reason and these headphones are just adding the extra ring connections to the same plug for the sake of backwards compatibility (we still use aircraft first developed in the 70s). Back then, replacing headphones would have been even more expensive so deterring theft sounds like a very valid reason. I'd also suggest that the extra prong helps reduce how much the plug can move if yanked by a passenger. Therefore the connector in the seat (which isn't too easy to replace) is less easily damaged.
The real answer is that there are two reasons for the two prongs.
The original two-prong plugs are, indeed, to make it so people don't take the headphones (and, alternatively, to make it so people have to rent headphones from the airlines but adapters made short work of that). Airlines tend to now give you throwaway headphones in economy (if any at all) that are much cheaper to produce instead, and those will usually just have a normal 3.5mm jack like everything else.
The plugs in the video are for noise cancellation for the business/first class headphones as stated, while being backward compatible with the earlier two-prong plugs and normal 3.5mm plugs. There exist alternative versions of this plug as well. One uses the normal two-prong (dual mono, TS) plug for audio and a second 2.5mm prong (TRS) for the ANC, arranged in a triangle. And more recently, a version of that 3-prong plug that actually replaces the prong with flat contacts, pogo-pins on the jack and magnets to hold it all together. This to help stop people from breaking the jacks.
3:40 ... also this way they can control the noise cancelling from the plane. So it can be disabled during the safety briefing or whenever there's an emergency.
I remember using pneumatic headphones back in the 1980s, I still remember how the music on the inflight entertainment system used to pause when an announcement by the cabin crew was being made.
Do these have a similar feature?
Yes. Then entertainment system still pauses.
I remember as a kid flying with Qantas, and they used the pneumatic headphones up until around 2000. I remember because my dad taught me a prank where you unplug your neighbour's headphones then blow into the plug, and being disappointed when the electronic ones came out.
0:10 "you can not keep the large headphones". This isn't actually a universal truth, and varies between airlines. My approach is to assume that I can not keep them, but if the packaging that they come in says otherwise, then it's game on.
Good video! One thing I'd like to point out is that the processing of the active noise canceling signal is most likely done in an analog fashion. you only need to amplify the signal and then invert it which to can do with 1 or 2 opamps which are dirt cheap. Doing it digitally would be way more difficult and expensive.
Pro "just the" tip: if you sort of half-insert your regular 3.5mm into these your earphones will work as normal. On some planes when you go all the way in, the sound cuts off on one side (by design, I'm guessing)
I suppose another benefit of having the in-flight entertainment system handle the noise cancellation is so that they don't need to worry about batteries either, since (IIRC) active noise-cancelling headphones need power to do the noise cancellation.
hey, remember that "file types that are actually .zip files"? can you make a part 2 for files like sb, sb2, sb3, (those are for scratch, a kids programming language made by the Massachusetts Institute of Technology btw) and more file types that are just zip files or like zip files?
@@unknowniblox Like .jar files or the newer Office file format?
I always learn new, interesting things from this channel.
I assumed each seat had to 2 jacks so couples can enjoy the entertainment together if so desired. Had no idea of the double jacked headphones.
Not to mention the older plane headphones which are even weirder as they are just plastic tubes with no driver at the end, or even any electronic components at all.
are couples sharing seats, too? pretty sure that's against airline policies.
It's been a while since I've been on a plane with any kind of headphones jack at all. Normally you bring your phone, your headphones and connect to the plane's wifi to access whatever limited stuff they have.
I remember those jacks from the 90s. They stuck around until this decade.
That one is new to me. Latelly I could just plug my stereo headphones on the top plug at the arm-prest and it would work in stereo just fine. But WAY back in time, like, 2009, I did receive some of those cheap phones witht those double plugs, and both were mono, having only the tip and the ground, no microphone feedback for noise cancelling at all. That feature is completly new for me 😁
WAY BACK ... 2009, LOL. For me way back is 1960s
@@Axel_Andersen things change fast 😜
I too have never seen the microphone opening in the headset. For a proper cancellation, you need independent microphones for each ear because the signal comes at different times (or phase).
This connection goes way, way back; and I believe it is for noise reduction not noise cancellation. I know this dual plug connector has been around since the early 70's at least (I remember seeing them as a kid, and some audio gear we had actually had "airplane adaptors" for just this thing). Likely it isn't doing noise cancellation at all and doesn't have any microphone. Rather, it is a balanced signal (L+, L-, GND; R+, R-, GND). The advantage of this is that it cancels out common-mode noise. So aircraft electronic noise that gets picked up by the wiring to the jack and up to the headphone get cancelled out as the same noise is present on the + and - polarities of the signal and is thus easy to filter. With just a simple extra bit of circuitry, it can be built to detect when only one jack is plugged in and switch the pinout to L/R/GND, allowing unbalanced audio to a standard headphone set. This would be an update to the original design which I believe used just TR (mono) plugs, one for left, one for right, unbalanced. Adapters came with compact cassette decks for a while that converted that setup to a TRS stereo headphone jack.
This makes the most sense. Simple, and also explains why regular headphones (single trs) would still hear in both ears, although only left or right.
This makes a lot more sense. You're running a ton of signals past each other over a long distance with a lot of instruments inside a Faraday Cage.
This is just left over from the early days of having a few monitors over the aisle for showing movies. If you wanted to hear the audio you had to rent their ‘special’
headphones or earbuds, which were collected before landing so you would have to pay again on the next flight. Planes are incredibly high tech, airline senior management not so much! Some have made the massive leap to a single jack stereo, so only a couple of generations behind now.
On a Qantas flight I took once it was back when they were one use disposables, so you could take them with you if you wanted. Yeah, I did for the same reason, the novelty connector and as a kind of souvenir. The hostess actually gave me a couple more pairs that other passengers had discarded!
I was on a Qantas long-haul flight this summer, returning to the US from Australia, and they were still handing out these cheap disposable headphones to people who wanted them. I took a pair and found out they were actually just normal earbuds connected to an adapter. Feeling clever, I detached the adapter and plugged in my own headphones. It worked well. I was even able to reuse the doodad later on a US domestic flight, but I seem to have misplaced it recently.
All it would take to do noise cancelling in that setup is for them to invert the phase of whatever the mics are hearing and mix it with the program. Inverting the phase of an audio signal is basically the same thing as swapping the red and black wires on a speaker. It's something that wouldn't even require a microchip; it could be done with discrete components alone.
All the reasons you've listed are probably correct, but, I know that one of the major reasons is so that they (the plane) can control the audio -- this is the reason why you can still hear the official announcements even while wearing (apparently) active noise cancelling headphones...they can control what sound to 'pipe' over & above the audio you're listening to -- esp. useful in emergencies as well as for many types of announcements.
Why couldn't they intercept the audio stream of a normal jack? That seems to be more a function of what they're plugged into than of the headphones or interface itself.
@@reidprichard Hmmm...Interesting point. Maybe the internal electronics are different?
I'm afraid I'm not qualified or knowledgeable enough to answer that legit query. Sorry...
You wouldn't need more contacts for that. Until very recently, those used to simply be two mono jacks side-by-side, and yet the in-flight entertainment system already had that functionality.
@@reidprichardThey usually do just interrupt entertainment for announcements.
@@Cr_nch glad I'm not crazy - I thought I remembered hearing announcements come through a standard headphone jack on one flight.
Maybe you're too young to remember, but this was the standard before seat back entertainment systems. The noise cancelling is new, though...they definitely just had one channel per prong, at least in economy. I still have adaptors for these plugs, but not every airline uses the same spacing.
I thought they would have been a small version of XLR where you get + signal, - signal, and ground. The idea being that you take the difference of the signals and the EM noise would get cancelled while the signal get amplified.
Far more along the lines of what I was thinking too - given the amount of high voltage circuitry and transformers so tightly packed into aircraft I wouldn't be surprised if there may have been some resonant buzz which could be cancelled, similar to a balanced cable.
Emirates have this plus an extra plug making 3 prongs, the extra one is a power supply for the sound cancelling feature which is very good. Plug in, switch on and turn the volume to zero and all the background noise disappears, plus they are totally useless if you steal them as they will not fit anything else.
Qatar uses the 3 prong system, too. I was wondering what the third prong was for, but I didn't want to plug anything into it just in case it was powered, and I fried my $300 Bose headphones. It sounds like I made a good call. :(
Moving the noise cancellation computing to something outside the headphones also means that they don't need to provide power or charging via the jack. No need to have hundreds of potentially dangerous Li-Ion batteries all over the plane that are constantly getting charged and discharged.
Noise cancelation is surely out of phase if the signal needs to go from the headset to th computer in the seat and then back to the speakers. That delay messes up the noise canceling feature. And that's assiming they are designed the way you described it.
Qantas has these, and so far all the other airlines I've flown on both here (Australia) and overseas that had headphone jacks had the normal single jack that you could plug your own headphones into. And I thought Qantas was the only airline that had these dual jacks. Thanks for clearing that up.
Interestingly enough regarding this is that Qantas actually changed the adapter on the headphones from the hardwired dual-prong set up on the headphones to single jack with an adapter, so you _can_ more easily use other headphones.
The point about plugging in one prong and the audio still works for both ears - is it because both holes actually play stereo audio so people can plug in the 2 prong headphones whichever way and still have the stereo audio
I think the propagation delay of the signal would not be in the perfect phase, and why it didn't work that well. Time it take to reach the computer, get processed and sent back. I think it would be more successful if they just focused on canceling the engine noise with central cabin microphones placed in zones (ignoring people noise),and process a noise cancellation signal for the passengers in that section and apply that to the audio signal in that section.
This is very unlikely. delay of propagation and treatement are way lower than any perceptible human one. after all the highest freq is 20kHz. 50 microsecond is an eternity for sound processing.
@@tatoute1 Just a quick note, it needs to be significantly less than 50 microseconds, maybe 5 uS or less. But not that big an issue, ANC is primarily required upto 5kHz, after which passive noise cancelling works pretty well.
Given electricity travels at lightspeed I wouldn't have thought that little cable would add much in the way of propagation delay vs processing on-chip inside the headphones :p
I strongly question the idea of using a computer to do that. All one needs to do is to invert the microphone signal in amplitude and mix it in into the audio signal. This can be done in the simplest case just with the wiring. The most complex technical system I would expect would be a simple inverting amplifier, realized with a cheap OpAmp, which is only used because the microphone would need some power by itself and thus one needs to bring a powerline to the seat anyways.
No need to throw a computer at it, even if µC are really cheap these days. It just would complicate the whole system by the need of A/D conversion of the audio and microphone signal, mixing them together and have them D/A converted for the headphone. Much to complicated for something which can be done much simpler with good old analog electronics.
The secret behind noise cancelation is in the placement of the microphone, which must be as close as possible to the ear.
@@kallewirsch2263 lol it's not that simple. Everyone would be doing that if it was like that, and ANC headphones wouldn't cost what they cost now.
If you simply do what you said, it will 1) also filter out the audio and 2) still not work because to cancel out, the signal needs to exactly match up.
First video of yours in a while I really enjoyed! :D
this would be a really cool way for some headphones to support balanced audio, have 2 mono jacks with 2 prongs, but of course a 4 prong different sized plug is what actually ended up being used.
They can do balanced audio with a single jack. Higher end Sony Walkman have them. They're standardized.
@@NinjaRunningWild I know that's literally what I said
They do. You can buy them from several manufacturers. They're just not that popular. Your configuration is wrong, though. For balanced operation, each channel needs 3 conductors. 2 for signal and 1 for ground. Also, its not the connectors that make something mono or stereo, its the recording. A 2 channel audio system for stereo music will have 2 identical or mono channels. What makes stereo its own format is how the 2 channels are recorded. On playback, the stereo signal goes to 2 mono channels.
@@AT-wl9yq
The definition of a balanced signal is that it doesn't use ground, it uses a pair of conductors - two - in which a dedicated return conductor carries (only) the same current as the other conductor in the pair. Two conductors - signal A and signal B.
See for example CAT5 and CAT6. Those are balanced signals, so there's no ground.
If the signal wires are neither twisted nor coaxial, the balanced signal wires may be covered by a SHIELD. That shield may be sheet metal on a PCB, may be a braid, etc - it's not connected to the signal, if it exists, and is not part of a balanced signal channel. If there is a shield, it may or may not be connected to a resistor, a capacitor, or both. Those resistors and/or capacitors may or may not be connected to drain to chassis ground. In any event, if the shield exists, it exists to protect the two conductor signal. It isn't part of the signal.
@@senseisecurityschool9337 Balanced headphones sound like a total gimmick. There is no need to reject noise at headphone level signals, what kind of interference is going to penetrate that strength of signal to any noticeable effect?
Proprietary connection means they can control who can access it. In coach they often make you pay extra to use them. If they accepted standard connections they couldn't demand money for renting them.
Those are most likely balanced headphones. Balanced operation would make sense because its a much better way to transfer an audio signal when you need to use long runs of cable. Every seat on the plane has to be wired for audio. That's a tremendous amount of cable, as opposed to what you would have on a personal system. Also, there is a "noise cancelling" aspect to balanced operation, but it works a different way, and achieves a different result than what most people think noise cancelling is.
For balanced operation you need more conductors than a typical single ended design. If you look at the connectors on the airplane headphones, you'll see that they are a TRS design. The 2 rings break the connector up into 3 zones. Each zone is a conductor. (For balanced operation, any 3 conductor connection will do. XLR is also a popular choice.). On regular headphones, you have a signal and a ground, + and -. On balanced headphones, you have 2 signals and a ground, + + -. The 2 signal conductors carry the same audio signal, except that they're the opposite polarity. This is for noise reduction, not noise cancellation. There's a difference. Noise cancellation is done so you don't hear noise around you when you are using the headphones. Balanced circuits deal with things that effect the signal going through the wire itself, not external acoustic noise.
You can buy balanced headphones, but they're just not that popular. The headphones themselves will have 2 connectors like the ones in the video, and your headphone amp will have 2 inputs. The only difference between the airplane headphones and balanced consumer headphones, it the connector itself. The ones for the plane use 2 trs mini jacks, and the ones sold to consumers use either 2 full size 1/4 inch trs jacks, or xlr. It doesn't really matter because electrically, they are all identical.
I think you're right. A balanced line makes a lot of sense in airplanes, even more if you consider everything runs on AC at 400 Hz. The whining of the 400 Hz in some planes is very noticeable when the crew uses the PA system, imagine having that tone the whole trip well inside your ears!
This seems the best explanation to me. I just so happen to work with these systems on this airline so if I remember I’ll go digging through some documents and see if I can find out if it is the truth
Out of 700 replies, you are right on the money for explaining balanced analog audio over long cable run. The noise cancelation is in the context of reducing electrical noise or interference, not in the context of reducing acoustic noise offered by active noise canceling headphone such as Bose QuietComfort. On newer airliners that have individual entertainment panels, each panel provides amplification for the headphone with a much shorter cable run, thus unbalanced stereo TRS 3.5mm jack.
Balanced transmission (which are just differential pairs) are not the same as balanced headphones. When headphones are "balanced" it means they do not share a ground, each channel gets its own negative going back to the amp that made the signal. This helps eliminates crosstalk between the channels but does little else to suppress noise. Noise suppression isn't really needed in headphone signal lines because of the impedance most headphones operate at. Your typical bookshelf speaker operates at around 4 ohms, while the lowest you'll typically see headphones' impedance is 8 ohms (in the really cheap ones). My over the ear headphones have 300 ohms of impedance while my in-ear's have about 26 ohms of impedence.
@@roberttseng6147 Except they aren't because Joe literally showed the schematic for the headphones and it shows the signal paths go to microphones, lol. Did people even watch the video? Wtf.
The last plane I was on, they used one of these two-jack setups, but their provided headphones used a standard single 3.5mm jack to plug into a two-jack adaptor. So I could easily unplug the provided headphones (which were next to useless anyway) from the two-jack adaptor, plug my own headphones into it, and then plug the adaptor into the plane's sockets, and it worked perfectly fine.
I actually asked about this on a flight and the attendant said it's so the plane can feed emergency info right into your headset if necessary. He never said anything about noise cancellation.
Overriding the entertainment system audio in an emergency should be easy to implement, though, so that makes no sense to me.
I think they just made that up lol
@@ThioJoereminds me of AI hallucinating answers
I suppose most of the airline crew except maybe the pilots and technicians don't even know this.
@@ThioJoe Yeah probably lol.
The last time I boarded a plane, I got a dongle that converted a 3.5mm stereo jack into a dual-3.5mm jack.
I kept it for a while for the novelty, but eventually “destructively dissembled” it.
I always thought it was just so you are forced to buy headphones from the airline instead of using your own.
I'm surprised you flew on a plane with these jacks. Usually, I see everything just plugging into the infotainment screen in front of you now a days. I've not seen a plane with a collective movie screen in quite some time.
"forced to buy headphones from the airline"
What airlines force you to buy headphones?
@@BatCaveOz If you wanted to watch the movie. Obviously if you didn't want to watch, then you didn't have to buy them.
@@BatCaveOz*Most* charge a fee to rent them unless you're in a higher seat tier where they might be included.
@@NinjaRunningWild Turkish Airlines gives them away in economy. The quality is real bad though.
It also allows the plane to turn off noise cancelling in an emergency
I'd be curious if the off-loaded noise cancelling might be designed to prevent the headphones from also canceling the "ambient noise" of cabin announcements.
On flights that I've been on, they just cut off whatever in-flight entertainment you're listening to and pipe the announcement directly into the headphones. it's part of why nowadays I just watch things from my phone instead of bothering with the in-flight stuff.
They used to be passive earphones with the speaker just behind the socket, two holes for two ears.
Maybe when they went to an electric system it was so they didn't have to replace the aircraft seats with different ones with different holes punched in them?
This is actually a really interesting way to reduce the cost of the headphones so that you don't lose so much money when idiots like Joe take your headphones
Also, I see an open source hardware project in somebody's future to build a microcontroller based system that will not only adapt these to normal 3 and 1/2 mm or maybe even Bluetooth but also provide the missing noise cancellation processing
I wonder if having the noise cancellation done on the plane rather than in the headphones would also allow announcements from the pilot/stewards to bypass/override the noise cancelling and be routed right into passenger headsets, for those who are distracted!?
Theo quickie
The reason for that is that the airline used to sell you bad earplugs you couldn't use your own. the plug has been around for so long before sound cancellation the first time I flew in the 90s, so you had to pay to be able to listen to the movie they played on the plane
These used to be a thing but I haven't seen a plug like this on an airplane in about 15 years.
@travis1240 I flew internationally last month, the "premium" seats have this, the "economy" seats use regular phono Jack's and disposable ear buds passed out by the flight attendants. (The 14 hour leg was in a "premium" seat, the 4 hour domestic leg was in "economy," so I saw both.)
here I was thinking they were balanced mono to reduce RF interference... ( ground, + and - signals, where one gets flipped so they're either both + or both -, but since they both had the same interference BEFORE one was flipped, after the flip one now has inveted noise so adding them together cancels the noise out)
The real reason is safety. They can turn off the cancellation remotely, so you can listen emergency announcements.
Why not leave NC on and pipe the announcement through the headphones?
they override and pipe the announcements through the sound system, like travis said. this channel seems to have fostered an audience of people who just talk out of their asses.
"This video is just a alleby so you could steal the airplane headphones... Isn't it!?" 😂
My guess would be that the main reason for implementing noise cancellation like this would be so the headphones themselves don't need to be powered. If the active noise cancellation was done in the headphones themselves (like your consumer ones) they would need power. Either a lithium battery or externally provided power would come with risks that wouldn't suit use in an airliner cabin.
You know if you pry off one of the prongs, you can plug them into things like a regular pair of wired headphones (btw it works but only with some)
Also dont worry, I asked before taking them
Still don’t know if I can take him serious
That might explain it now with contemporary ones, but planes have had a weird connector for their headphones for _decades,_ long before noise-cancellation (and back then, it was mono pins). Iirc, back in the 70s, they'd actually use one for the music/movie, and one for announcements.
The noise cancelling circuits would be part of or very near the socket in each seat as
1) the noise to be cancelled would be unique to each ear piece.
2) you'd want the minimum delay (distance) in generating and applying the inverse noise signal onto the output back to the relevant ear.
3) so you could isolate this extra cost to particular higher paying seats like first class or business class.
Note - cabin broadcasts override all the airline entertainment audio signals so that you can still hear the broadcast on your own stand-alone noise cancelling haedphones
Correct it's part of the socket. For sure, I know.
Checking if anything is plugged in into one or both jacks is really easy. The little spring contacts that make contact with the plug while plugged in do the trick. They are resting on a contact on the other side, and if you plug in your plug they get lifted from that contact. So all you need to do is so monitor that contact. Most times is done on the ground contact, so the computer checks if there is still ground potential on that contact, so no plug is plugged in.
Lol, I just saw your comment about it...
There’s also another type of headphone plug with four segments just for the speakers it’s called a balanced output usually used on high end headphones
Two prong adapters are definitely not used specifically for noise cancelling, as they were in use before noise cancelling headphones existed.
As well, most newer airplanes have switched to using the standard single 3.5mm port, which presumably would include any noise cancelling features that the airplane includes.
I would also guess that having it like that makes them able to disable the noise cancelation when there is an announcement in the plane
Yes, I have seen this elsewhere - it's used in Audiometric testing devices. I also have memories of an early 2000s Minidisc player with this on - maybe by SHARP?
Fascinating video! I've got a hypothesis to share. The microphones integrated into the headphones seem to be designed for capturing high-frequency noise only. Meanwhile, the low-frequency noise appears to be picked up from another source within the plane. Since low-frequency noise tends to be consistent across environments (similar to using a single subwoofer in home theaters but multiple speakers for higher frequencies), this approach not only makes the design more cost-effective but also explains why you hear some noise when you plugged in your own headphone.
low frequency has higher carry and penetration than high frequency, to better explain. this is why sirens modulate between two tones; a low one so you can hear it coming from far away, and a higher one so it is easier to tell what direction it is coming from as it approaches (low freq sounds can be heard farther, but are harder to locate source.)
It's a typical feature to detect when the jack is plugged in. In this case there is just a bit of logic that will properly multiplex all output signals to the one jack if the other isn't used.
You got me down the rabbit hole of two-prong airlane headphone jacks. I discovered that premium cabins and legacy airplanes have three-prong headphone jacks that do the same thing, except two jacks provide a left and right audio channel while the third offers power to the headphones. All of the extra prongs are for redundancy and discourage passengers from taking the headphones.
Thanks for the bit at the end. Im pretty sure I used a regular apple earphone when I travelled previously and plugged it into one of the ports and it worked fine.
I don't recall seeing the dual jack on any of my flights. I did assume it was related to the pneumatic headphones I remember in my younger days. The concept of central noise cancelation is intriguing, even if not effective. Thank you for this. Following now!
Another reason could be that with the audio processing happening in the plane's electronics, the headphones can be completely passive devices without needing batteries. If the active noise canceling was happening in the headphones they would need to be powered in some way.
An advantage of that setup is that the noise cancelling can easily not filter out announcements. It could even be set so that the voices of the flight attendants is given special treatment so that they can be heard. Regular noise cancelling headphones WILL filter out the voices of peoples around you along any actual noise present.
Then, for using your own headphones... A simple switch in both sockets can do the job. Only a single socket is used ? Act like a regular audio socket.
I remember the headphones on planes having these back in the 90's, too. We were allowed to take our headphones, too. They just had a regular 3.5mm jack that was plugged into an adapter with the 2 jacks on it and you could take it off and use them normally. So, there goes that theory.
I suspect it also could have to do with grounding. Since planes are always electrified having a second pin could make sure the excess static would have a shorter path to ground rather than going through you crating a noise in the headset in the process.
I used to have headphones where the second prong could fold away for daily use and then you would just flip it out whenever you were on an airplane. It had noise cancellation, but it was really just a bunch of white noise LOL
I suspect that it is originally an anti-theft thing as I recall these from back in the day when they started with electronic headphones. I don't think audio-cancelling was even a thing back then? I think back then they were two mono plugs.
Its quite easy to detect, if there is a normal pair of headphones connected: there are 3.5mm jack's that includes switches, which are activated if something is plugged in. If only one of the two switches per socket is activated, it says to the computer to deliver Stereo sound to just this plug.
Also a single stereo 3.5mm jack is a lot easier to snap off when you get up out of your seat in very cramped conditions. That double jack is very solid.
Actually the left prong is for the headphone speakers and the right prong is for speaking directly with the captain.
This setup is so old I also got headphones with this connector way back in 2008 when I had my first transatlantic flight. Interestingly enough, those had a hinge on one of the prongs so it could be folded up when using with regular 3.5mm sockets.
electronically, it is VERY simple to see if there is connection between 2 electronic connections, and looking at the 2 prong pinout, there is connection between the prongs, so mic ground is on one prong and a mic output on the other and vice versa for the audio drivers, so it detecting a standard set of headphones might just be by reading continuity between the prongs
I took home a set of these from a qantas flight ages ago, and they had noise cancelation built in. In that setup, the extra connectors on the dual 3.5mm jacks were used to feed 18vdc to the headphones from the seat plug to power them up. Note at 4.10 the picture shows dual mono 3.5 jacks, not stereo ones. Must be yet another use case out there for those ones ….
most PCB mounted 1/8'' and 1/4'' TRS jacks have a pin that detects weather the plug is physically present in the jack, so all you have to do is assume that if only one of two jacks is connected, its a stereo headset and you should output audio on both channels. that is how I assume this works. that or detecting the different impedance between the plane headset or yours.
the main reason is so that the airline personnel can interrupt the audio and make announcements that you will be able to hear with the headphones on.
I think the big value of having the processing in the plane and not the headsets is because you don't need any power in the headset, i.e., no need to charge them.
looks a little like the Kenwood audio jack found in many handheld transceivers.
However the Kenwood jack combines a 3.5mm and a 2.5mm with one being used to transmit and the other to receive.
I normally unplug the headphones from the airline and plug my own into just one of the slots and it has always worked for me.