Finally a smart approach. A simple google search shows the principle of sound deadening. You make the parts that vibrate heavier. Why i from the beginning of watching these vids thought they were not thought through covering every inch without seams. That is way past the point of diminishing return.
The 9-3SS is already a fairly quiet car, but they do suffer from road noise intrusion, especially at the rear. I had one of my Auto Engineer colleagues in the car a while back and he identified that as an issue. I hadn't really noticed as the driver. I went a little OTT on this project, but it has been very successful. The car is proper quiet at the back now and the hifi sounds sooooo much better
In the future to make it simpler, you need to place the sound dampening material on the flattest surfaces. That's where the noise will mostly come from.
I haven't replaced the liners yet (because I'm doing shocks and rust protection) but drove the A50 near the JCB plant yesterday where it is concrete (and a flippin' noisy surface) and can report the car was much quieter on the concrete than previously, even at intercontinental ballistic speeds. Looking forward to driving this section nearer Xmas when I'll have the liners back in. On normal tarmac it's near silent from the rear now.
14:30 you should apply the butyl to the metal inside of the wheel well, not to the the plastic liner. The butyl stuff minimizes vibration and resonance specific to metal, it does very little for plastic.
@@zelowatch30 Long story short, the mass-loaded vinyl is not worth even using if there's no layer in between it and the butyl layer. The butyl stuff is generally the first layer of sound deadening, it just stops the metal that you attach it to from vibrating while the engine is on. It comes with a heavy glue on one side hidden behind backing, you prep the surface with rubbing alcohol first to remove any residue, let it dry off, line up the butyl and cut it to shape if necessary, then peel off the backing and stick it on to the metal and press it against the surface with one of those roller things til the bumps go away. For interior surfaces generally after you put that on, you do two more layers, a sort of thin foam padding may or may not come with adhesive on it, and its job is to just be a layer in between the butyl and the last layer which is mass-loaded vinyl, which is basically just a really dense material which blocks a lot of sound, then you put the carpet or plastic trim back on top of it and hopefully it still fits. I have no idea if you'd have room for 3 layers between the wheel well plastic liner and the metal wheel well but I would assume not.
@@denbrisko1978 I believe the butyl is wrapped inside the foil, and there's a glue which is revealed when you remove the backing paper which sticks the foil onto the surface you are insulating. That glue is what holds onto the wheel well. If you tried to press the butyl onto the tire side of the wheel well, water will eventually get into the glue and you will have a big sheet of butyl slapping on your wheel, so you would definitely want the butyl on the opposite side of the wheel well from the wheel if you did want to use it there. I think generally people pry out the trim in the car interior with a trim tool and line the floor and area under the dash in the front half of the interior as opposed to lining the actual wheel well.
Last week I realized my tires were the main cause for the sound I was hearing in the cabin. Drove on a fresh stretch of new asphalt and the sound dropped hard. Barely audible anymore. Then that bit of road ended and suddenly the noise came right back... Now I'm contemplating doing this and changing my oem tires that came with the car with some aftermarket tires that are quieter.
@@CycloneCydWhat's the app you used for analyzing the sound (4:52)? I'm planning to do something similar on my 23 VW Arteon which has atrocious road noise intrusion.
Excellent video! You did little over kill with butyl, 20-40% is ok, knocking is your friend. I will add use closed-cell foam not flamable/ not soaking water is important, I used 2mm and somewhere in 2-3 layers. I will attack wheel arch in few weeks.
Thank you for the very well presented instructive video, particularly your constant reminder about the implications of adding extra weight around the vehicle.
I did the butyl sheet treatment to my '63 Beetle, and was amazed at the improvement. My 9-3 was already leaps and bounds quieter from the factory, but I'd be interested in seeing what improvements can be made with this.
I'll be doing the C1 next, but not so OTT as I did the Saab (with 260 horses, the Saab can spare a few for 20kg of sound deadening, lol). There's very little sound proofing in the C1s so not much of a manufacturers lead to follow, so follow the Saab lead. I'll do a video.
Glad to watch your take on this matter. I also have this planned for the future. There's a video from Spain "Saab 9-3 - StP Soundproofing | Audio-Equip". It seems that they managed to remove a lot of high frequency noise leaving a nice low frequency rumble. Not sure about the 18dBa drop. I've been to the brand site and checked the weight per m^2 they probably added about 30kg to the car. 😂 and about £500+ price tag for the material. I have the same philosophy as you do regarding the butyl layer, you don't have to cover all the surfaces, i.e., diminishing returns, on the other hand with the foam you do a full coverage which will catch the vibrations that escape from the gaps in the butyl layer but also absorb the rest. Also, from what I understand, each type of layer absorbs a specific range of frequencies. But the major question for me, it's, what brand to choose?
18dB. Holy moly that is a HUGE drop in sound. If they literally covered every sqcm with butyl and more then it _might_ be possible. I would have thought 10-12dB to be about as good as you can do. Exactly, there is a law of diminishing returns at work here. Both in terms of weight, cost and effort. As you say, diff materials work in diff ways and absorb diff freq ranges. When I get to the doors you'll see something completely different again. I've recommended Noico products in the description. Good quality without being mega expensive. The links are affiliate, so anytime you buy anything from Amazon, follow one of my links onto the Amazon site and I earn a small (2-4%) commission. A great way to support the channel at zero cost to yourself (and deprive Geoff Bezos of a few dollars, lol).
Really found this informative; your explanations and reasoning are very 'sound' (no pun intended!). I would love to know just how much difference your time and trouble was worth in terms of the difference it made in everyday driving. I've watched a lot of videos on this subject, and yours is the most comprehensive to date, however, I would love to see the decibel lever difference 'before and after' the mods, using the same exact road conditions. Thanks again...Cheers!
He addressed why he didn’t do a decibel level test. In total, the reduction in pure db is relatively small. But where it reduces db in the most relevant spectrum of frequencies is huge. Also, by lowering the pitch of the noise, you subjectively reduce noise by a noticeable degree. Sound meters don’t discriminate what frequencies it picks up. Our ears do.
Just did this on my 01' Celica GTS that has ZERO foam or sound deading in it as it is a light car. Haven't done the doors yet (important!) and the plastic panels are still off, but it is indeed noticeable and changes the experience of being in the car. Not a magic fix and the affect is quite subtle, but going from a big box of bare metal to rubber dampened and foam layered is quiet a change. Helps with thermal insulation too. Also of course it's going to make your speakers and sound experience MUCH better. The exhaust inside the cabin sounds MUCH better and clearer. This is the same reason I hung moving blankets on the walls of my room and put a lot of studio foam up. It's not exactly killing noise so much as it's trapping all the high frequiences bouncing around and making everything sound awful.
It does! Which is exactly why the OEs are 'skinny' with it (that and cost). With another half dozen sheets under the rear seat cushion, I've added about 12kg to the car. if I had covered every sq cm of panelwork, I could easily have added double that. The rear end of the car is incredidibly quiet now. When i go over expansion joints on motorways and dual carriageways now, i can hear the 'thump' from the front wheels, but not from the rear. The car is even pretty quiet on that horrible concrete near the JCB plant on the A50. I'll be doing the front end next and then I've got a few tricks up my sleeve for cutting road noise from coming in through the doors, ie cutting road noise from *_other_* vehicles
@@CycloneCyd Yeah, I will do it once the weather gets better; I still have the material. It just takes a little time also was interested to hear the difference for each panel. I wish you had shown how to tear down the 9-3 boot to the steel.
@@uselessproductions2364 The side trim is only held in by a few clips and pushed under the rear seat side bolsters. The carpet pulss out but has a loop round a seat belt fixing - I cut the carpet to get it out.
"Knock test" will let you know where your solid area's are while most panels or larger area's should have some decoupler. Yet be mindful where you vehicle suspension parts are attached, which transmits noise to the body which hardly ever gets mentioned. i.e. Struts, shock, springs and etc... Besides "boot and bonnet". 😁✌
VED varies with model (engine) and year. You're best looking it up using the VRM of cars you are looking at. My 2007 2.0T is £320pa. Only a V6 would be more
Very good video, very opens your eyes. As it is being said - you only need to cover about 25% of the surface to reduce a lot of noise, you don't have to cover everything. Good job, thanks!
It also insulates though, keeping outside temps out is part of the trade off. Covering all the floor and walls might add 50 lbs total in an suv on the high side, is 50 lbs really significant?
Not if there is an air gap between the foam and the arch, you'll notice I did say to only fit it where there is room. Plus, I shall be protecting my arches with Lanoguard before refitting the liners. There's some rustiness around the shock top mounts and I'm replacing shocks and mounts (as soon as they arrive!)
I will. Doing the Saab first partly because I had the rear end all apart for the new wheelarch fitment AND the Saab has decent sound proofing so is a good car to follow for the "manufacturers lead".
All that time, labor and expense for little gain. I choose to simply wear ear buds that work as hearing protection from outside noise and I can use them for music and phone.
Very remiss of me to not do before and after measurements, really. But yes, the car is loads quieter, especially for rear seat passengers, who have commented on the quietness.
It would have been much more useful if you had included a noise level measurement before and after application of noise reduction material. I have seen some videos that showed negligible difference. So the whole exercise and expense seem useless.
Best way to look at weight is to put it in the boot and drive around with it and see if you get a hit on your MPG. You will see more of an issue if your journeys are stop start rather than cruising.
I don't even have a driver's license and even I am interested in reducing tire noise. I was sitting in the rear as a passenger in a Mazda, going 110 kph. I could not take part in the conversation with the people in the front because of the tire noise.
Your ad hoc approach for what sound deadening mat does for wheel arches is completely bogus. You tapped on the wrong side of the wheel well. That is, you need to tap on the outside concave section of the wheel well behind the tire, not on the inside of the vehicle (the wheel arch, convex area). Much more importantly, a hand tap generates relatively low frequency noise while tire noise is all high frequencies much like white noise. You were listening to the wrong type of noise !
Sound is vibration. It needs to vibrate through the body panels to get in. Dampen the vibration of the body panels, dampen the noise coming through. Wrap it up in foam to reduce vibration through the air the foam replaces. Cover the foam in mass-loaded vinyl and it reflects vibrations back into the foam. All three steps do something, and the first two are plenty effective individually.
👉 How to super clean your windscreen: ruclips.net/video/nRox9i8rdDM/видео.html
Finally a smart approach. A simple google search shows the principle of sound deadening. You make the parts that vibrate heavier.
Why i from the beginning of watching these vids thought they were not thought through covering every inch without seams. That is way past the point of diminishing return.
Hands down the best video on noise reduction on the whole platform I appreciate it I’m going to sound dampen my ng9-3 this summer
i look in to that subject for a while and you cover more than many others, greta job explaining it
Absolutely fantastic video. Really make me want to do this.
I put sound deadening material only on flat areas. That where the metal resonates the most! Less is more.
Indeed, that's why you see shallow swages in flat areas.
Definitely something that needs to be done to my 9-3 as well. Thank you!
The 9-3SS is already a fairly quiet car, but they do suffer from road noise intrusion, especially at the rear. I had one of my Auto Engineer colleagues in the car a while back and he identified that as an issue. I hadn't really noticed as the driver.
I went a little OTT on this project, but it has been very successful. The car is proper quiet at the back now and the hifi sounds sooooo much better
Nice video. Great common sense from a smart guy. Thanks!
In the future to make it simpler, you need to place the sound dampening material on the flattest surfaces. That's where the noise will mostly come from.
Whilst that is true generally, the wheelarch is a 'special case', as it's directly over the source of noise
Damping, not dampening.
no @@garyvanremortel5218
@@garyvanremortel5218 it’s dampening in my car, bloody water leak! 😂😂😂
@garyvanremortel5218 go jerk off to your dictionary
Very comprehensive vlog Cyd, I shall employ your method! Thank you.
I haven't replaced the liners yet (because I'm doing shocks and rust protection) but drove the A50 near the JCB plant yesterday where it is concrete (and a flippin' noisy surface) and can report the car was much quieter on the concrete than previously, even at intercontinental ballistic speeds. Looking forward to driving this section nearer Xmas when I'll have the liners back in. On normal tarmac it's near silent from the rear now.
14:30 you should apply the butyl to the metal inside of the wheel well, not to the the plastic liner. The butyl stuff minimizes vibration and resonance specific to metal, it does very little for plastic.
But would it fall off? What about that with MLV over the wells plastic?
@@zelowatch30 Long story short, the mass-loaded vinyl is not worth even using if there's no layer in between it and the butyl layer. The butyl stuff is generally the first layer of sound deadening, it just stops the metal that you attach it to from vibrating while the engine is on. It comes with a heavy glue on one side hidden behind backing, you prep the surface with rubbing alcohol first to remove any residue, let it dry off, line up the butyl and cut it to shape if necessary, then peel off the backing and stick it on to the metal and press it against the surface with one of those roller things til the bumps go away. For interior surfaces generally after you put that on, you do two more layers, a sort of thin foam padding may or may not come with adhesive on it, and its job is to just be a layer in between the butyl and the last layer which is mass-loaded vinyl, which is basically just a really dense material which blocks a lot of sound, then you put the carpet or plastic trim back on top of it and hopefully it still fits. I have no idea if you'd have room for 3 layers between the wheel well plastic liner and the metal wheel well but I would assume not.
Is the butyl waterproof to use it under the wheel well?
@@denbrisko1978 I believe the butyl is wrapped inside the foil, and there's a glue which is revealed when you remove the backing paper which sticks the foil onto the surface you are insulating. That glue is what holds onto the wheel well. If you tried to press the butyl onto the tire side of the wheel well, water will eventually get into the glue and you will have a big sheet of butyl slapping on your wheel, so you would definitely want the butyl on the opposite side of the wheel well from the wheel if you did want to use it there. I think generally people pry out the trim in the car interior with a trim tool and line the floor and area under the dash in the front half of the interior as opposed to lining the actual wheel well.
what material would be better suited for plastic, I flimsy door trims in my car which rattle when the music is a bit loud, any suggestions? thanks!
Last week I realized my tires were the main cause for the sound I was hearing in the cabin.
Drove on a fresh stretch of new asphalt and the sound dropped hard. Barely audible anymore. Then that bit of road ended and suddenly the noise came right back... Now I'm contemplating doing this and changing my oem tires that came with the car with some aftermarket tires that are quieter.
My kid told her friend the other day "my Daddy knows everything" I am convinced this man knows everything.
He could be her Dad.
Love this! Would love to see how you insulate the engine noise/firewall
See here: ruclips.net/video/86FvMtB53l4/видео.html makes a surprising difference
@@CycloneCydWhat's the app you used for analyzing the sound (4:52)? I'm planning to do something similar on my 23 VW Arteon which has atrocious road noise intrusion.
@@KlmDet it's called Advanced Spectrum Analyzer. I've got it on Android
Excellent video! You did little over kill with butyl, 20-40% is ok, knocking is your friend. I will add use closed-cell foam not flamable/ not soaking water is important, I used 2mm and somewhere in 2-3 layers. I will attack wheel arch in few weeks.
I could have 'got away' with less, but she is whisper quiet now.
Thank you for the very well presented instructive video, particularly your constant reminder about the implications of adding extra weight around the vehicle.
I did the butyl sheet treatment to my '63 Beetle, and was amazed at the improvement. My 9-3 was already leaps and bounds quieter from the factory, but I'd be interested in seeing what improvements can be made with this.
Wow !!! Thank you Cyd !!
Welcome!
Thanks Cyd! I keep my C1 light… and I have to live with her tinny character. I’m fine with it. Take care - Martin
I'll be doing the C1 next, but not so OTT as I did the Saab (with 260 horses, the Saab can spare a few for 20kg of sound deadening, lol).
There's very little sound proofing in the C1s so not much of a manufacturers lead to follow, so follow the Saab lead. I'll do a video.
@@CycloneCyd Oh, thank you Cyd! I'm looking forward to this video. Have a nice day (here in Oberschwaben it's grey)...
What an excellent video, very well explained. Thank you
Also interesting to know how much all this efford have improve the NVH.
wise words from a wise man!
Thank you
I’ve had good results using a second layer comprised of foam lined Mass Loaded Vinyl.
Glad to watch your take on this matter. I also have this planned for the future.
There's a video from Spain "Saab 9-3 - StP Soundproofing | Audio-Equip".
It seems that they managed to remove a lot of high frequency noise leaving a nice low frequency rumble. Not sure about the 18dBa drop.
I've been to the brand site and checked the weight per m^2 they probably added about 30kg to the car. 😂 and about £500+ price tag for the material.
I have the same philosophy as you do regarding the butyl layer, you don't have to cover all the surfaces, i.e., diminishing returns, on the other hand with the foam you do a full coverage which will catch the vibrations that escape from the gaps in the butyl layer but also absorb the rest.
Also, from what I understand, each type of layer absorbs a specific range of frequencies.
But the major question for me, it's, what brand to choose?
18dB. Holy moly that is a HUGE drop in sound. If they literally covered every sqcm with butyl and more then it _might_ be possible. I would have thought 10-12dB to be about as good as you can do.
Exactly, there is a law of diminishing returns at work here. Both in terms of weight, cost and effort.
As you say, diff materials work in diff ways and absorb diff freq ranges. When I get to the doors you'll see something completely different again.
I've recommended Noico products in the description. Good quality without being mega expensive.
The links are affiliate, so anytime you buy anything from Amazon, follow one of my links onto the Amazon site and I earn a small (2-4%) commission. A great way to support the channel at zero cost to yourself (and deprive Geoff Bezos of a few dollars, lol).
@@CycloneCyd search on youtube for "STP Sound Test" the video with a speaker being covered with 3 different layers.
That’s one heavy car 🔥 I would trade weight for sound in any car!
Really found this informative; your explanations and reasoning are very 'sound' (no pun intended!). I would love to know just how much difference your time and trouble was worth in terms of the difference it made in everyday driving. I've watched a lot of videos on this subject, and yours is the most comprehensive to date, however, I would love to see the decibel lever difference 'before and after' the mods, using the same exact road conditions. Thanks again...Cheers!
He addressed why he didn’t do a decibel level test. In total, the reduction in pure db is relatively small. But where it reduces db in the most relevant spectrum of frequencies is huge. Also, by lowering the pitch of the noise, you subjectively reduce noise by a noticeable degree. Sound meters don’t discriminate what frequencies it picks up. Our ears do.
Just did this on my 01' Celica GTS that has ZERO foam or sound deading in it as it is a light car. Haven't done the doors yet (important!) and the plastic panels are still off, but it is indeed noticeable and changes the experience of being in the car. Not a magic fix and the affect is quite subtle, but going from a big box of bare metal to rubber dampened and foam layered is quiet a change. Helps with thermal insulation too. Also of course it's going to make your speakers and sound experience MUCH better. The exhaust inside the cabin sounds MUCH better and clearer.
This is the same reason I hung moving blankets on the walls of my room and put a lot of studio foam up. It's not exactly killing noise so much as it's trapping all the high frequiences bouncing around and making everything sound awful.
Great idea. I'm surprised at how much weight it adds.
It does! Which is exactly why the OEs are 'skinny' with it (that and cost). With another half dozen sheets under the rear seat cushion, I've added about 12kg to the car. if I had covered every sq cm of panelwork, I could easily have added double that.
The rear end of the car is incredidibly quiet now. When i go over expansion joints on motorways and dual carriageways now, i can hear the 'thump' from the front wheels, but not from the rear. The car is even pretty quiet on that horrible concrete near the JCB plant on the A50.
I'll be doing the front end next and then I've got a few tricks up my sleeve for cutting road noise from coming in through the doors, ie cutting road noise from *_other_* vehicles
super good job 😀
Thank you! 😊
Thanks for this video!
I have a question, putting dampening material on the wheel arches, wouldn't that keep water in some way permanently? Thanks.
Very good, Thanks !
Thank you for a great video!!
Shouldt we apply noise insulation to door panels also?.
wonderful video. thanks
Brilliant 👍
Hi,
Nice work ! How much weight is added after the insulation ?
I've done the same to the doors in my 9-3. I was planning to do the boot, but I kinda found that already enough in my saloon.
I'll be doing doors next. You'd be surprised how much road noise comes in the rear. This made a huge difference to mine.
@@CycloneCyd Yeah, I will do it once the weather gets better; I still have the material. It just takes a little time also was interested to hear the difference for each panel. I wish you had shown how to tear down the 9-3 boot to the steel.
@@uselessproductions2364 The side trim is only held in by a few clips and pushed under the rear seat side bolsters. The carpet pulss out but has a loop round a seat belt fixing - I cut the carpet to get it out.
"Knock test" will let you know where your solid area's are while most panels or larger area's should have some decoupler. Yet be mindful where you vehicle suspension parts are attached, which transmits noise to the body which hardly ever gets mentioned. i.e. Struts, shock, springs and etc... Besides "boot and bonnet". 😁✌
Love the vids! I'm looking at getting a 9-3 and was wondering how much the road tax costs? Many thanks!
VED varies with model (engine) and year. You're best looking it up using the VRM of cars you are looking at. My 2007 2.0T is £320pa. Only a V6 would be more
Very good video, very opens your eyes. As it is being said - you only need to cover about 25% of the surface to reduce a lot of noise, you don't have to cover everything. Good job, thanks!
It also insulates though, keeping outside temps out is part of the trade off. Covering all the floor and walls might add 50 lbs total in an suv on the high side, is 50 lbs really significant?
Is it possible to fill the insides of the chassis and body with expandable foam like the new s-class has?
Thanks 🙏
great video
What I did on my small hatch, I installed mats on the roof, doors and boot. Next project would be floor and firewall.
I just did the doors on my 8th gen civic . I plan on doing my trunk and front wheel wells tomorrow. I also bought rain guards for wind noise
I changed my tyres from Yokohamas 235 /40/19
To Pirelli 245/40/19s
The ride quality and noise reduction was very noticeable
Does this sound deadening would work or at least lessen cabin drone from an exhaust?
Is foam on top of a wheel arch liner not going to lead to a rust problem?
Not if there is an air gap between the foam and the arch, you'll notice I did say to only fit it where there is room.
Plus, I shall be protecting my arches with Lanoguard before refitting the liners. There's some rustiness around the shock top mounts and I'm replacing shocks and mounts (as soon as they arrive!)
How about doing this with a vid on your C1 ?
I will. Doing the Saab first partly because I had the rear end all apart for the new wheelarch fitment AND the Saab has decent sound proofing so is a good car to follow for the "manufacturers lead".
All that time, labor and expense for little gain. I choose to simply wear ear buds that work as hearing protection from outside noise and I can use them for music and phone.
@@vintagemxer9165 The DB scale is non-linear, but exponential. A change by even a few numbers is significant.
missing a step, mass loaded vinyl. using all 3. really makes. the big. difference.
Was there a reduction in dB?
Very remiss of me to not do before and after measurements, really. But yes, the car is loads quieter, especially for rear seat passengers, who have commented on the quietness.
@13:09 "Clean your backside with soap and water. that's where we'll be sticking some sound insulation. ."
The golden ear audiophiles are breaking out in a cold sweat thinking the exhaust vibrations is getting to your amp affecting the sound.
Hello what app do you use to measure the noise?
For just sound level (dB) I use an app called 'sound meter'. For the spectrum analyser I use 'advanced spectrum analyser'
It would have been much more useful if you had included a noise level measurement before and after application of noise reduction material.
I have seen some videos that showed negligible difference. So the whole exercise and expense seem useless.
Good video. Just remember, no matter how quiet it is, Saab now, sob later.
when i saw that in my car i was questioning why it is fixed. and what really that thing is
What about glass?
Db is geometric so every increase of 3 db equals a double of power
Most of the road noise comes from the front . Front wheel drive ! Come from the tyres and driveshafts .
What exactly is this BOOT that you are referring to?
In the UK the "boot"is what is called the "trunk" in the USA.
So how much weight was added all together?
About 5kg.
Thanks so much - I’ve gone and got some now and it’s made a difference for sure
Best way to look at weight is to put it in the boot and drive around with it and see if you get a hit on your MPG. You will see more of an issue if your journeys are stop start rather than cruising.
Awesome video but won’t the foam in the wheel arch linner absorb moisture / water 🧐
Not if you buy the proper stuff, which is closed cell foam and so cannot absorb water 👍 and if it's neoprene based it won't rot.
@@CycloneCyd right ok thanks man 🤘🏻
I don't even have a driver's license and even I am interested in reducing tire noise. I was sitting in the rear as a passenger in a Mazda, going 110 kph. I could not take part in the conversation with the people in the front because of the tire noise.
I understand that! This massively reduced noise in the rear for passengers.
Just buy the good tiers
My car got noticeably quiet with a new set of tires.
New tyres are always quieter than worn tyres. Especially when wet.
Noise canceling earbuds works very well for me😂
Unfortunately, very illegal to drive with earbuds in.
Your ad hoc approach for what sound deadening mat does for wheel arches is completely bogus. You tapped on the wrong side of the wheel well. That is, you need to tap on the outside concave section of the wheel well behind the tire, not on the inside of the vehicle (the wheel arch, convex area). Much more importantly, a hand tap generates relatively low frequency noise while tire noise is all high frequencies much like white noise. You were listening to the wrong type of noise !
On the contrary I think it is you who have missed the whole point.
you missed a spot
İTS not a noise reducer , İTS just a vibration barrier ...
Sound is vibration. It needs to vibrate through the body panels to get in. Dampen the vibration of the body panels, dampen the noise coming through. Wrap it up in foam to reduce vibration through the air the foam replaces. Cover the foam in mass-loaded vinyl and it reflects vibrations back into the foam. All three steps do something, and the first two are plenty effective individually.
Why care
5:20 Nice Plants!
OR ....
just buy a car from a good manufacturer
What I did on my small hatch, I installed mats on the roof, doors and boot. Next project would be floor and firewall.