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On a tangentially related note, that trim piece you pointed out doesn't fit very well on my car and its always bothered me. The edges and holes don't line up precisely. Is this the case for anybody else?
Ah... In exchange for my helpful advice, you can send me the battery trim cover. I've inquired locally, but all the car parts recyclers are closed due to Covid-19 layoffs.
CCWW,
I will be going down the same path as you for noise control, but not so soon.
Here is what I will do :
01. First, identify the offending noise frequency. This must be identified as the sound absorber or reflector we will need to use, more so the sound absorber material....only works well on certain frequency spectrum.
This is called "noise reduction coefficient". Most so called acoustic material, has data sheet stating which frequency they work best at and how much it can reduce the loudness level of that particular frequency.
The simple rule of thumb is, the lower the frequency, the more mass/weight of noise reduction material is needed. 300Hz and below is a bit-ch to work with.
I have a tester microphone which I will use for fine tuning my own and friend's home theater system. I will use this microphone for my car sound reduction project. https://www.minidsp.com/products/aco...SAAEgLasfD_BwE
The software is free https://www.roomeqwizard.com/
02. Identify the source of the noise, its strongest location/source.
Do not be suprised, certain shape, say a wheel well/fender, can "amplify" a sound. Its called a standing wave
03. To absorb or to reflect ? This is the question.
Why absorb noise when we can reflect* it as much as we can and then absorb what leaks into the car interior. *This is assuming the sound can be reflected away from car under carrieage.
Our E series has some sort of black sound reducing sheet at the under-carriage, but at both sides only and not at rear axle to rear bumper.
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I think reducing noise at exterior before it can enter the cabin is very important. It won't be easy I am sure, but its a homework to think about.
How is an S-Class exterior under carrieage noise reduction treatment like ? Perhaps we can learn a thing or two from an S-Class.
Excellent points, @S-Prihadi . My preliminary measurements have included the use of a RTA spectrum analyzer. I have not saved any data yet that I can post. However, there is a lot of lower frequency energy that decreases significantly as frequency increases. I have not seen any particularly hot frequency zones or evidence of standing waves yet.
Considering that much of the energy that we are trying to eliminate is in the sub-500 Hz zone, I believe that absorption will be largely ineffective, especially beneath the carpet and near the wheel wells where there is not room for several inches of absorptive material. The most likely to succeed strategy is blocking the low frequencies with mass loaded vinyl (MLV) decoupled with a thin foam layer. Solid reflecting materials like MLV have much better low frequency acoustic properties than practical absorptive materials. Their optimal frequency in terms of efficacy will much higher than our frequencies of greatest concern, however they are still the best option. The thicker the MLV the better it will perform at low frequencies, but this is limited practically by weight and thickness. I am hoping to use mostly or only 1lb/ft^2 (5kg/m^2) MLV. Perhaps a double layer or 2lb/ft^2 (10kg/m^2) if I can identify particularly bad hotspots like the wheel wells.
While reflecting sound works best with as much coverage with the MLV as possible, identification of hotspots for extra-thorough treatment could help the final result. However, I don't know how to practically achieve this. The sound in the car seems so omnipresent and the cabin so small, that I don't think simply moving the measurement microphone around can reliably pinpoint hotspots. Perhaps this will just have to be done via deduction and intuition unless anybody has suggestions on a more reliable empirical method.
If anybody has information, photos, or links I would like to read more about S-Class acoustical design. I have not been able to find any detailed information on this myself. I think it could be quite instructive indeed. I do know that one member has reported spraying his underbody panels with sound deadening material on the outside and then painting them, he reports an improvement, although I don't know what kind of roads he is dealing with.
In some older yachts they use thin lead lined acoustic foam as sound insulation for its mass. I managed to get 1 piece back in the 90s.
But those days we were more concerned of the marine diesel turbo whine, so rather high frequency. Our marine diesel exhaust are sea water injected and quite good at noise reduction.
Do you have a thickness of lead you are considering, @S-Prihadi ? That website gives two example thicknesses, they compare 0.03" lead to some other materials. This is nearly 2lb/sqft. Then they mention 4mm, which would be over 10lb/sqft, which would be implausible for most areas as easily 50 sqft or more coverage could be needed.
I found this fascinating image of the W222 S-Class acoustic treatments. Sadly there wasn't any more detailed description than what is contained in the slide. The trunk and rear seatbacks do get a lot of attention. This encourages me to redouble my focus on insulating the back of the fold-down rear seats.
Wow, that's something how much 'absorbing' and 'attenuating' they do in an S-class. Obviously they spent a bunch of time tracking down and handling all different sources and pathways for noise in that car.
I've always thought the same engineering/methods/materials could be applied to any car, but that manufacturers deliberately create a model hierarchy in which the more expensive cars are quieter.
Last edited by Tom in Austin; 06-15-2020 at 08:31 PM.
Knowing what I've learned about lead, I would not place lead any place in the car where it can outgass lead vapor in Summer heat. That means nothing exposed to cabin air (behind the rear seats, for one). Not to mention you really should limit any handling of raw lead. You need to wash hands thoroughly after handling.
There are more modern materials that don't have lead, and are lighter, too. The car stereo places sell Dynamat, Fatmat, Kilmat,etc. I don't know the differences between them. I've used Dynamat before in small bits to stop noisy vibrations and it works well. But expensive in large pieces. Here's a review of the current brands...
Do you have a thickness of lead you are considering, @S-Prihadi ? That website gives two example thicknesses, they compare 0.03" lead to some other materials. This is nearly 2lb/sqft. Then they mention 4mm, which would be over 10lb/sqft, which would be implausible for most areas as easily 50 sqft or more coverage could be needed.
I found this fascinating image of the W222 S-Class acoustic treatments. Sadly there wasn't any more detailed description than what is contained in the slide. The trunk and rear seatbacks do get a lot of attention. This encourages me to redouble my focus on insulating the back of the fold-down rear seats.
I have no idea yet on how thick/thin it would be, but if I do use it it will be exterior use as sound deflector. Perhaps below that spare tire plastic well.
How to mount it, I have no idea, but I would think leaving air gap between the lead sheet to the plastic mould of spare tire well at say 1cm or so.
I saw that image you posted too, yesterday during a search, it is interesting.
I also found interesting information from an NVH engineer at this forum :
================================= I'm speaking with a little authority in this area as I'm currently doing a systems analysis of NVH performance & interactions between parts. Cars (road vehicles) have:
Two NVH functions (engine, road).
Four NVH characteristics (absorption, isolation, damping, sealing).
Different materials are used in each area for various performance interactions. Heavy layer felt in the carpet for example increases absorption, polystyrene blocks under the carpet to prevent your feet touching the floor metal. Baffles along the inner wing prevent booming. Bitumen meltsheets increase damping performance. Foam strip aids in sealing.
What Carl did was very belt & braces (and ofc no holds barred open wallet vs OEM ) and it basically added absorbtion and damping to all drumming (metal skin) surfaces. What no one can do, without a test rig or full vehicle CAD and FEA, is to determine which panels give the most NVH contribution (and at what engine speed, road speed, road type...)
Here's an interesting one for you. The A class does away with the hood insulator altogether in favour of two constrained- layer meltsheets. These are bitumen pads with a thick aluminium foil layer on the outside face; vibrations enter, hit the aluminium: air boundary and bounce back, almost entirely cancelling out the incoming vibration (think of two opposing sine waves merging to form zero). Craiglxviii, Aug 15, 2017
I wish I could post what I'm doing at the moment but it's all under NDA. Shame really as there's a number of very helpful diagrams.
Imagine a simplified plan view of the car. Draw a line from the front and rear edges of each wheelarch to the centre point of the driver's seat base. You'll end up with a squashed X shape. That is the pathform that radiated tyre noise takes (well, to each seat, but it's the driver we're primarily concerned with). Now, imagine that in three dimensions so you get a height vector as well as length and breadth. The portion of the wheelarch liner that gets felt pads is that which, when viewed from the hub location, points towards the driver's head. So, the location can (and dependent on OEM, may do) change dependent on RHD/ LHD and also model spec/ grade- VAG for instance have different levels of NVH pack applied dependent on grade. The top and bottom grade Golfs are something like 8dB average apart.
Now take your view of the driver's seat from the hub and widen your view angle to cover both front seat headrests. Where that angle intersects the plastic wheelarch liner (wheelhouse) is where the felt pad needs to be applied. NB this is for absorption not damping, so we're after felt/ carpet and not dense material).
Now go to the wheelarch itself, that is to say the body metal inside of the plastic wheelhouse we have just NVH'd up to the nines. This has an issue whereby vibrations from the engine, and from the tyres rolling over the road, can set up and cause all sorts of nasty harmonics. These can be perceived as sound or vibration in various body panels- side doors are notorious for picking this up due to their large drumming surface. So we have to either damp out (easy) or prevent (hard) standing harmonics from forming in those arches. Easiest way to do this is to fit bitumen pads usually on top/ inside-facing of the arch. The precise location will vary model to model, engine to engine (and tyre to tyre too, which is why changing tyres can have such a dramatic effect). Craiglxviii, Aug 16, 2017
The S klasse has really, really heavy NVH system already applied, something like 20-22dB average reduction across the vehicle. Trying to reduce down beyond that goes way past diminishing returns! Craiglxviii, Aug 17, 2017
Knowing what I've learned about lead, I would not place lead any place in the car where it can outgass lead vapor in Summer heat.
This outgassing I never knew if only at say 50-60 celcius , assumed potential car interior at a very hot day, I know outgassing when doing soldering but much more heat involved.
If in water it can "leech" out its poison I know.
Thanks my man ..
My solution when road noise starts getting to me is to just remove my hearing aids. It gets much quieter then.
However, I'm guessing that this is not an option for you. Therefore, I'm suggesting that you look into ear plugs that block certain frequencies as a less expensive alternative to modifying your car. You can find some examples on this website: https://wiki.ezvid.com/best-earplugs-for-musicians
Link: Earplugs for Musicians
My solution when road noise starts getting to me is to just remove my hearing aids. It gets much quieter then.
However, I'm guessing that this is not an option for you. Therefore, I'm suggesting that you look into ear plugs that block certain frequencies as a less expensive alternative to modifying your car. You can find some examples on this website: https://wiki.ezvid.com/best-earplugs-for-musicians
Link: Earplugs for Musicians
I think we are also needing excuse to tamper with our cars, just for the pure fun on tinkering
I actually tried the earplug thing for a while with my last car, which was much louder. I even equalized the stereo so that it sounded more natural while wearing earplugs. Even though I don’t mind wearing earplugs to sleep in noisy places or at concerts, I never got used to it. I also want to have a quieter car for conversations with passengers.
And, as @S-Prihadi points out, it’s a fun project. I’m fascinated by sound and acoustics so it’ll be interesting to see if I can achieve anything meaningful.
I should be cleared to use both of my arms at the beginning of July from my motorcycle accident injuries. So I’m probably going to start ordering materials very soon.
So far I’m going to be employing a mix of 3M Thinsulate, 1lb/sqft MLV, 1/4” closed cell foam, and Second Skin Dampifier butyl rubber/aluminum. I’ll also be adding weatherstripping to air seal the fold down rear seats.
I’m also planning on retrofitting the original optional acoustic laminated glass, however I have no idea how long it will take to receive from Germany. I’ll also need to get it tinted and installed so quite the process. If anybody has procedure documents for the glass replacement I would consider doing the install myself.
I recently started on a newly acquired W218 CLS 550. I was experiencing what I felt was excessive road noise. Mine comes mostly from the rear of the car so I started with the trunk, specifically the spare tire well. I installed a layer of butyl rubber damping material called 66 Mat and then covered that with a layer of Noico Red closed cell foam.
I don’t have any measured data but both my wife and I feel it has made a significant difference.
Based on this success I am going to continue with the rest of the trunk and see how much better I can make it.
This electric Mercedes is serene enough to challenge the S-class's reputation as the king of quiet... Mercedes even stuffs acoustic insulation into the body vents that equalize pressure between the cabin and atmosphere to muffle road noise. (The company does this on some, but not all, gas vehicles as well.)
Does anybody know the location of these ports on the W212? And if they are insulated like on the EQC? If not, I would certainly like to add some if the locations can be determined.
+1 for AS3's being on the loud side. I had a set of Pirellis on my Lexus and they were lovely in every respect -- except snow, where they were not quite useless. I replaced them with AS3's and immediately noticed an increase in sound levels inside the car.
I’ve ordered the four side windows in the optional laminated safety glass with acoustic membrane. They correspond to the original option code 839. Two of them have to come from Germany so I’m not sure how long it’ll be. I’ll need to get them tinted and then I’m going to attempt the install myself thanks to documents provided by the invaluable konigstiger.
I will be sure to report on the results and I’ll attempt to quantify it with measurements. However I will be installing some dampening (although not planning on MLV for now) on the metal inside the door and the back of the door card while the door card is off. So that will confound the measurements somewhat.
If anybody else is interested, here are the part numbers for the four windows. Please note these are W212 only, S212 has different rears. I also don’t know if these are compatible with pre-facelift cars.
Fascinating. Do they come with some sort of factory tint to match the regular glass in the car, or are you aiming for a different type/level of tint than the standard?
Fascinating. Do they come with some sort of factory tint to match the regular glass in the car, or are you aiming for a different type/level of tint than the standard?
According to the parts advisor at the MB dealer they will have a standard factory tint, meaning very light. I believe that for the normal glass different tint levels are available corresponding to different markets, but for the 839 laminated safety glass with acoustic membrane, there is only one option.
I will be doing a light to moderate tint to match the rest of the car and the outgoing windows.
I’m entering the final planning phase for my initial efforts which, beyond the acoustic windows that I’ve already ordered, will include MLV/CCF behind and under the rear seat, under the trunk mat, behind the trunk panels around the rear wheel wells, and possibly under the rear deck. I will also add 3M Thinsulate behind the trunk panels, in the spare tire well, and anywhere else it will fit in the aforementioned area. I’m hoping to have everything measured and ordered tomorrow.
To give an example of the noise levels from the pavement in my area, a local two lane highway is being repaved right now. The new surface is unusually smooth even for brand new road in Oregon and it is wonderful. I measured 59.5 dB at 65mph on it with the climate fan off. A touch of wind noise, a touch of diesel growl, but utterly serene. No complaints, could live with this noise level forever. As soon as it changes to the old pavement, which isn’t even nearly as bad as it gets here, I measured a 9 dB jump in average level! Cruising at 65 mph is about 68.5dB with tire roar overwhelming all other sounds. Roughly this means that tire noise is at least 8x louder than all other noises from the car combined!
I am rather interested in @S-Prihadi’s suggestion of identifying particular frequencies of annoyance. While I’m not sure how I can address specific frequencies without much greater engineering resources than I have, it would be interesting to know what component of the sound I find so annoying. Perhaps I can record the road noise and place notch filters on the sound and listen to see when I no longer find it so bothersome. But regardless the tools that I have at my disposal for acoustic treatments will be broadband by nature.
Reads like you have roads in Texas. We have some in Georgia but not like Texas. One item you did not mention, tires. Tires are the only items on our cars with road contact......... so we only have two choices to lessen noise, the road surface, and tires. I've been playing with cars for 60 years and I've been through all the things you mention, wasted tons of money and the best results have always been tires. Mercedes spends millions on sound testing to eliminate cabin noise in our E models based on cost vs value out of the factory. As far as tires go I owned an Infiniti G45 with Michelin's and it rumbled on the roads you described. I changed to Toyo Versado Noir 245x40x18 and it was quite as a Cadillac. Check this site, https://www.tyrereviews.co.uk/ Not sure if Toyo's are available on the west coast Soooo good luck with your noise issue.
Reads like you have roads in Texas. We have some in Georgia but not like Texas. One item you did not mention, tires. Tires are the only items on our cars with road contact......... so we only have two choices to lessen noise, the road surface, and tires. I've been playing with cars for 60 years and I've been through all the things you mention, wasted tons of money and the best results have always been tires. Mercedes spends millions on sound testing to eliminate cabin noise in our E models based on cost vs value out of the factory. As far as tires go I owned an Infiniti G45 with Michelin's and it rumbled on the roads you described. I changed to Toyo Versado Noir 245x40x18 and it was quite as a Cadillac. Check this site, https://www.tyrereviews.co.uk/ Not sure if Toyo's are available on the west coast Soooo good luck with your noise issue.
^^^^^^^ Yep, tires. One can spend thousands adding dead weight to the car with insulation to yield minimal improvements. Instead, I would poll a few tire dealers in the area what their customers say is the best (better) tire to deaden road noise. If the roads are as loud as the OP says, then the local tire dealers will be aware of customer complaints, and will have this feedback from drivers who encounter the same roads the OP does. Then, with 2-3 tire choices identified, I would shop replacement tires. IMO, this is where the best sound suppression can be achieved for the least expense.
Tearing the car apart to install sound suppression can bring sound problems of its own if the insulation is not securely attached.
I’ve received two of laminated acoustic windows. The other two are still on their way from Germany, I’m hoping they’ll show up soon.
I test fitted the front passenger side window today. No problems at all with thickness or anything else, so now I feel confident getting all the windows tinted once the other two arrive. I will have them tinted before installing them so there are no visible edges to the tinting.
The installation was remarkably easy with two people. Taking the door panel off, installing the acoustic window, and putting the door panel back on took maybe 90 minutes on the first try while learning and going slow. Doing it the second time to put the old window back in took half the time. Would have been far harder without documents from the invaluable Konigstiger. I know he doesn’t accept PMs but I wish I could send him a box of pears or something, his help is incredible.
Also, the doors are held on by orange plug clips. 9 on each front door and 8 on each rear. They have round foam gaskets to seal around the plug hole and decouple the door card from the metal door panel. The foam gaskets were completely shot on all the clips, totally flat with no spring. I’m going to replace all of them with the hopes that will help kill any little rattles in the door.
I’ve received two of laminated acoustic windows. The other two are still on their way from Germany, I’m hoping they’ll show up soon.
I test fitted the front passenger side window today. No problems at all with thickness or anything else, so now I feel confident getting all the windows tinted once the other two arrive. I will have them tinted before installing them so there are no visible edges to the tinting.
The installation was remarkably easy with two people. Taking the door panel off, installing the acoustic window, and putting the door panel back on took maybe 90 minutes on the first try while learning and going slow. Doing it the second time to put the old window back in took half the time. Would have been far harder without documents from the invaluable Konigstiger. I know he doesn’t accept PMs but I wish I could send him a box of pears or something, his help is incredible.
Also, the doors are held on by orange plug clips. 9 on each front door and 8 on each rear. They have round foam gaskets to seal around the plug hole and decouple the door card from the metal door panel. The foam gaskets were completely shot on all the clips, totally flat with no spring. I’m going to replace all of them with the hopes that will help kill any little rattles in the door.
Good god I guess there's a first time for everything. I'm sure you checked for the USA DOT approval. I imported an MB back in the 1980's and had to have the glass changed.
06-11-2020, 10:20 PM
) and it basically added absorbtion and damping to all drumming (metal skin) surfaces. What no one can do, without a test rig or full vehicle CAD and FEA, is to determine which panels give the most NVH contribution (and at what engine speed, road speed, road type...)
