The Surprising Science Behind Noise Cancelling Headphones | The Secret Genius of Modern Life - BBC
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- Опубликовано: 25 авг 2024
- So it makes sense, but it also doesn't 😅 #SecretGenius #iPlayer
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Hannah Fry uncovers the secrets behind the miraculous technologies of the modern world, revealing the mind-blowing stories behind their invention.
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Hannah Fry is an amazing science presenter!
I met her once on tv, I don't know why she keeps popping up for me.
As a person who knew a bit about phase/polarity inversion (being a musician) i’ve still found this video informative and clear! Great work!
People are going to ask why the second speaker doesn't completely cancel the sound from the first one. As I understand it, the reason is that the speakers are not in the same place, so the second sound waves are not the exact opposite of the first ones -- each will reflect and reach you by some paths that the other one doesn't. But ear buds are in the place where all sound enters your ear and can cancel all of it.
Excellent demonstration and explanation.
... the more you know. Noise-cancelling headphones are an essential piece of kit for long-distance flights.
Now, if we can only tackle the flight-cancelling airlines problem...
@@SayAhh Apparently that works by another flying back in the opposite direction at exactly the same time as yours, cancelling out your flight. Possibly.
@@SayAhh Service-cancelling train companies could also do with being informed that you can't just send buses down the same route to cancel out the problem
No they aren't. The only essentials for long haul flights are a passport and aeroplane.
Imagine how nice it is for pilots now
I remember watching this demonstration on Tomorrow’s World sometime in the late seventies or early eighties! Think it was first developed for fighter jet headphones to reduce engine noise impact on pilots.
I wonder what happened to the stay clean glass demonstrated once on the same program?
And so many other things. It was an amazing programme huh? I remember these magical things called CDs. Silver discs, and I think they covered one with cigarette ash too prove the CDs resilience. I miss CDs but not really the cigarette ash.
I had to wear noise cancelling headphones to sleep due to noisy neighbours but noticed increased ringing in my ears...not sure if it's actually related tho.
It is, because noise canceling tends to produce high frequencies. Ideally, you would not hear them, because they are too high. But they are there. Meaning, your ears are exposed to more air pressure waves than without the headphones.
@@1stSilence Thanks for the explanation!
I had no idea that is how noise canceling works.
Hannah Fry’s presenting for BBC now?! Get it girl! 👏🏾🎉
She's been on the BBC for years!.
@@ogribiker8535 God I love her.
Presenting for BBC since at least 2018. Where you been?
@@intotheshred oh my bad i been in Scunthorpe, not Southampton..
Isn’t this or a similar principle used for radio beamforming, like in WiFi networks? Receiver devices transmit data back to the main transmitter on signal strength and the transmitter then modifies the beaming amplitude so that waves in the direction of the receiver are amplified and those in all other directions are nullified, using the same principle of inverse transmission.
My uncle is deaf, his ears cancel all the noise,
so he wins.😌
Destructive interference? Similar to the bright and dark fringes in Young's double slit experiment?
Phase cancellation, oh yeah!
how does the mic know what to cancel out and what not to? that's the big question.
Whats the difference between what a £600 noise cancelling headphone does vs a cheaper one that uses ANC?
Capability of the ANC processor and algorithms.
Quality, across all audible frequencies. It uses a microphone or two, near the ear canal to sense the noise pressure that gets amplified, inverted and added to the signal.
If that mic is not low-self-noise and flat frequency, the result can be noisier, and have some frequencies boosted.
I had a pair 22 years ago that worked well, but I could hear people climbing stairs 15 m away through two doors.
Awesome :D
Hmm, I believe and Arthur C Clarke short story had this....
I had to watch because of your red hair
1 + (-1) = 0
It’s math in action. It makes sense but feels like magic.
Can we do with light? I need that badly in my apartment.
Where does the energy go?
Whats happening is that the speaker cones are in anti-phase. As one travels out, the other is travelling in. The positive sound pressure in the room as produced by one speaker when it moves outwards, is being cancelled by the negative sound pressure caused by the other speaker cone travelling inwards. So where does the energy go? it actually travels back and forth between the two speaker cones as they cycle in and out, in anti-phase. That leaves no net sound pressure from the speakers to impact the observers eardrums. Full cancellation would require more rigorous demonstration conditions of course, but you can certainly hear (or not hear) the cancellation as demonstrated by Hannah.
Demo would have worked better if they'd recorded the tone with a mono mic, equidistant between the speakers
..and at a lower frequency. A 200Hz tone would cancel far better than the 500Hz tone she used.
Yeah, but...analyzing the sounds around you will take time amd the gemerating the opposite curve and a speaker reacting will take time. So there must be a delay, which means the noise cancelling can't be perfect. Unless you have a very uniform noise.
There is of course a slight delay, it's not perfect but it still makes a significant difference.
The delay can be simply brought down to 1 or less milliseconds. So ...
There's no analysis, it's just a microphone feeding back the ambient/environment sound out of phase. The only time taken is the time for an electrical current to travel through the system.
@@mhagainThat's what I immediately thought of :)
I have the smarts! Finally!
I must inform mother! :)
There has to be a delay from processing, but it probably isn't significant. The maximum frequency humans can hear is around 20kHz, so a sample rate of 100kHz would be far more than enough, especially when you consider that we're not really interested in cancelling the highest frequencies anyway. 100kHz is a pretty tame processor speed, most small chips are rated in mHz at least.
That's so neat
Why noise cancelling give a bit of headache?
ahhhh. This appears to be how binaural beats work. I use the frequencies to help me sleep via brainwave entrainment/entrapment. I have lifelong chronic insomnia and have discovered that certain different frequencies listened to in stereo work better for me than any other sleep aid.
Sorry, but that's pseudoscience. There's been a recent systematic review if you're interested, by Ingendoh, Posny and Heine (2023). It's published in PLoS One, so is available through open access.
@@Grim_Beard Works for me when I use it. Your pseudoscience mileage may vary.
She could explain ice to eskimos, such a dream of a woman...
I couldn't understand how she is putting in the inverse audio just by switching the cables?
Audio signals are sine waves. This is an alternating current: the signal is centered on 0 V. The higher the volume, the higher the voltage. So that sine wave has one half with a positive voltage, and one half with a negative voltage. Switching the wires flips these.
She swapped the cables so the electric current flows in the opposite direction.
It reversed the phase so the up part of a sound wave becomes down
By reversing the red and black wires, she is causing one speaker cone to move out and in while the other moves in and out. i.e They are now in anti-phase, which is why manufacturers colourcode speaker wires. You must have them both wired the same way, otherwise you get unwanted sound cancellation, particularly at bass frequencies. If you have a hifi, try it. The sound goes all weak, lacking bass and sounds kind of phasey... imagine a boat with two propellers. If you put one of the propellers on backwards, then one propeller will push the boat while the other one will pull the boat. The boat won't go anywhere. Same thing here...
The video has audio auto gain meaning we can’t hear the difference at the first few
When they make noise cancelling airplane cabins.
I just sounds the same to me
❤️❤️❤️❤️❤️
Noise cancel culture.
damn she fine
🥱
I think they are missing so so many details in this...
No, they don't ...
It was explaining it in a way that most people should be able to understand. Although some don’t seem to WANT to understand.
Yes, to the point where it is misleading and wrong.
She should be teaching us about mRNA technologies and how to have pfaith in the science of the The Science 💉😵💫📺🇺🇦😷🧘♂️✝️🏳️🌈💗🤡
This explains by Physics.
I learnt how to save money on noise cancelling headphones. I can just reverse the polarity on one of the speaker wires instead, much cheaper!
Yeah, right, because the sound you want the headphones to cancel is the one coming from the headphones. Maybe you can just unplug it, dude.
Would have to be mono, and it still would just lower the volume.
Thanks for the replies. For anyone else reading my OP was a joke, don’t try it for the helpful reasons given in the replies…
The only problem I can see with your solution is that your brain would become liquefied and leak out through your nostrils
Lol I’m still non the wiser as to how it works after watching 😂
"The sound wave wobbling the air." Because in thick Britain the concept of 'vibration' is just too much to grasp! 🤯
This is a basic demonstration for children...
@@TheRugFace No it isn't.
Anyone who’s ever run a sound system knows this - it’s why you never connect your speakers out of phase…..certain way to totally kill your bass.
Be very careful with these... They are very new and their effect on your hearing is yet to be fully understood.
I had a pair 23 years ago and they were not really new then. I’ve never heard of any adverse effects and in aviation they’re widely regarded as the premium headsets. They’re not exactly witchcraft so I think they’re very unlikely to present any unforeseen dangers. The worse issue I’ve noticed is if the battery runs flat the passive noise reduction of active headsets is usually not so good as with wholly passive units.
Do you hear that? Do you hear this? Did you hear it?
But the question is, does this also protect your ears from loud noise if it “inversely copies” the sound?
There is no loud noise if the noise is cancelled
Word to the wise- don't accidentally hit gravel with your weed eater with noise canceling turned on. Extremely unpleasant and loud noises will occur.
Who doesn't know about phase cancellation?
@@stephjsinclair no. But come on. Phase cancellation…..
Yay! Phase cancellation!
...and they charge you an extra 1000000.99% for the privilege of them, quite literally and simply, flipping the polarity of the additional ear mic.
They don't charge that much more at all, a comparable non-ANC headphone will probably cost ~50% less at most. Yeah the cheapest earbuds vs the most expensive ANC bluetooth headphones have a vastly different price. ANC in headphones is also a lot more than flipping the polarity on a mic, you have to play the cancelling waves without ruining the music playing or creating an unpleasant 'pressure' for the user. Most modern headphones also allow tuning in the environment and a lot of this requires processing both for cancelling and pass-through.
have you heard of the word "interference" , and sound is not transverse wave
I'm sorry, but your channel with 70000 videos makes too much noise.
Could this title be any more CLICKBAIT? Is this the BBC or some kid in their bedroom??
This is not how ANR is done. Made way too simplistic, but also wrong, for the uninformed public. 🤦
headphones don't work, the background noise is just too loud. the earbuds are just a fancy thing. white noise cand be created only if u create yourself a louder type of noise so u can cover the shit you're hearing from the ppl and things around u
She Needs noise cancelation, to block out all the facts coming out about the Jab.
Not wrong
Batman did it first. Goodbye.
Every professional and hobbyist audio engineer understands that. Astonishing how many people come out, be loudmouthed, and at the same time present their stupidity as if this were a fortitude. :-((