retna7

Spot on!

This is an important point.

Here is what I used:


Used all three pieces.

Largest diameter for the front, smaller for rear , and center piece directly behind the magnet (attached to the actual door shell).

Open cell foam > Closed cell foam for this application.

This impacted the mid bass response much more than the reduction in vibration (NVX / Mass Loaded Vinyl) but requires the removal of the rivets.

I used Rivet Nuts so now I have screws where the rivets used to be.





NVX is on the back side of the panel vs the front.

Works the same either way but makes for a better install on the back vs the front.

ccww

Very nice! That's essentially the same as the OEM MB ones, although the latter are a tad deeper.

ccww

I found a significant problem in the data for all measured runs. There is some kind of high frequency transient at the beginning of most runs. I don't know if it is from tapping the record button on the screen, although I doubt this, or some kind of electronic or electroacoustic artifact of the measurement system and microphone activating. I had to go back and scrub the erroneous datapoints from all previous data. Too much has changed to show right now, but the standard deviation of repeated runs in terms of frequency is dramatically improved:



With the new modifications to the data analysis, I finished analyzing the data for the difference between laminated acoustic windows (839) and normal windows. The perception is of substantially reduced wind noise, much less sound by my left ear as I drive, and a reduction in noise from other vehicles. The data is interesting, I will dispense with difficult to read spectra, unless anybody requests them, and simply show 1/3 octave band graphs of the difference between the noise with and without the windows. The very smooth road at 65 mph where non-road noise should predominate has a graph largely as expected:



There is a reduction in high frequency noise, which should be associated with wind noise. This averages -0.9 dB from 630 Hz up.

The graphs on rougher roads are less conclusive. Unfortunately the before and after runs were performed after a tire rotation and balance and with the later tire pressures about 4-5 psi lower, both of which confound the data. Wind is also impossible to perfectly control for and should be considered to confound all the data to some degree.




Both graphs feature a marked decrease in noise around 80-125 Hz. This seems unlikely to be frequencies coming through the windows. Perhaps the door panel damping or the tire rotation and balance could be associated with this change. The 65 mph asphalt test shows the expected reduction in high frequency noise from the laminated windows but the 75 mph concrete test does not - perhaps in the latter the wind noise is subsumed by road noise. Most oddly, both tests show an increase in midrange cabin noise around 500 Hz to 2.5 kHz. I do not have a good explanation for this finding. There could be differences in the noise generated from the tires on the road after rotation and at a lower pressure. I need to have the pressure increased before running more tests.

I also wonder if, when road noise rather than wind noise predominates, that the laminated windows, which allow much less sound transmission, actually trap road noise inside the cabin instead of letting it pass through to the outside. This is inline with the frequencies observed to increase in amplitude and would explain why MB includes more cabin insulation with the 839 package, even though they did not advertise a benefit beyond the window difference. It is similar in theory to the car stereo dB racers (who compete to get the highest possible dB reading inside their vehicles) soundproofing their vehicles heavily not to keep noise out, but to keep the sound from their stereos inside.

Any theories on this odd finding would be very interesting, although it could well just be due to the tires or inter-day measurement variance.


I installed the 839-associated fender liners today. There is not a huge difference in construction considering the nearly $400 which they cost. They seem to be identical to the standard fender liner, but with a thin, plastic-wrapped acoustic blanket attached to the inside. The area that it covers is pretty large, however. The old fender liners were filthy, so it was nice to put some new and clean ones in. The process was simple and I managed to do it with only jacking up the car, not removing the wheels. However with the working position it wound up being quite a tiresome job.


Old on left, new on right.

There are seven specified damping strips (2x bituminous and 5x rubber and metal foil) specified around the wheel wells for 839 in unknown specific locations. I created a thread trying to figure it out to no avail and also obtained a copy of WIS which had no specific information on the matter. I was hoping that when I removed the fender liners that there would be an obvious location for all the pieces but no such luck. There was only room for the bituminous strips and nowhere that seemed suitable for the any of the metal-backed ones. After lots of pondering and shining flashlights in every nook and cranny, I believe that some or all of the damping is supposed to go on the metal fender's wheel well housing, but on the inside of it which is completely inaccessible without cutting and welding. I admitted defeat on the metal-backed pieces and installed the bituminous strips at the most suitable location on the metal under the fender liner, approximately facing the rear seat bolsters in the cabin. I also added about 1 sqft of butyl-rubber and aluminum foil damping sheet on the metal under each fender liner for good measure, focusing on the front and inner sections that are nearest to the passenger cabin.

There are also 4x specific fiber absorbing blocks of somewhat mysterious location specified for 839. I also asked about them in the thread linked above. I hope that I found the correct spot for them. There are small holes facing inwards in the metal structure behind the rear seat through which I was able to push the fiber absorbing blocks near to the location of the inner side of the metal of the fender's outer wheel well. This seems to correspond as well as I can find to the diagram and makes functional sense.


I have not had a chance to take any measurements. I did take about a half hour freeway drive. I wouldn't say that there is a dramatic difference, which I did not expect considering the thinness of the insulation on the new finder liners. However, the stretch of freeway wasn't particularly smooth and it seemed to be less noticeable than normal, more like a nicer section of road. This is indeed the goal of the project and hopefully this impression is borne out with measured improvements.

After so much exploration of the insulation and layout of this vehicle I am becoming increasingly convinced that the single most effective modification to reduce road noise will be a large sheet of decoupled MLV that spans the entire rear folding seatbacks side to side and from the rear deck to the rear bottom of the rear seat cushion, beyond the side bolsters, and to the edges of the cabin where the sheetmetal and door seals meet. Properly constructed, this will block noise from the rear wheel wells and trunk from reaching the passenger compartment very effectively. I'm looking forward to making this piece in the future, hopefully within a few weeks, and testing its performance.

S-Prihadi

CCWW,
Try a read on this one : https://www.jstage.jst.go.jp/article...1/23_1_17/_pdf
Page 22 sone zone is interesting.
Where is your mic located during all these test ?

ADD: also a good read
https://www.jvejournals.com/article/19935

Darel

WOW what an outstanding thread. I'm jumping in late so I'll admit I didn't read a lot of the technical stuff. However this has plagued me since I got my car. It's a complete assault on my ears. Here's what I've done.

Did spare tire well insulation with Dynamat. Possibly a slight difference but not really.

Took the car in for warranty work complaining of road noise. At 100k+ miles my goal was to get them to replace the control arm bushings, which I wanted done so I didn't have to do it 3 months AFTER the car goes out of warranty in December. They did this but they also had a couple of TSBs they applied. All in I got:

- control arms plus control arm bushings replaced.
- Transmission mount replaced
- They applied a TSB that basically said the engine mounts could be "binding up" and transmitting road noise. It basically involved loosening all the engine mount bolts, allowing the engine to settle itself, and retightening. Hey, it's free and worth a shot in your own garage, right? Maybe Konigstiger can provide more info if you need it. FWIW I have a 3.5 gas engine so it may not be applicable on your car.

Then a week later I took the car for new tires. My #1 priority was tire life, so basically I bought the tires I could find that were still all-season but had the longest treadwear warranty. I was sick of replacing tires every 9 months or so. I ended up with Nitto Motivos, which were at the same time inexpensive, highly rated for road noise and drivability, and had a 60,000 mile warranty, far longer than any other tire. This was a week after I had all the above work done. The difference between all the tires I'd had before - Pirelli, Conti, cheap Chinese crap - was significant. The car was now, while not silent, completely tolerable to me, to the point I probably won't pursue the road noise anymore, unless you come up with a genuine "A-ha!" fix.

I did also look into a specific Goodyear tire that was supposedly designed for road noise reduction above all else (QuietTread? SilentRide? or something maybe?) but they were expensive, and not well rated in other driving factors.

For what it's worth I did some SPL meter tests comparing the E350 to my '09 Audi S5 V8 with a lowered suspension and a straight-pipe exhaust, and believe it or not they were identical. And they were on the same Nitto Motivo tires too. Unacceptable that the E350 can be as loud as a straight-piped V8 Audi with frameless windows and a tighter suspension, that's supposedly more performance-oriented and 5 years older!

Good luck, I'll be watching this.

LILBENZ230

Odd.. my E350 seems very quiet and it is rolling on OE Continentals that were replaced during CPO process and are all at 8/32nds. I've had Nitto Motivo tires as well in the past and they are fine tires, for sure.

Darel - you're saying the CPO warranty covered these suspension components?

pierrejoliat

I am getting great information and learning a lot from you guys, it amazes me as to what lengths this has gone. I applaud you! I still believe my 12 Luxury is quieter on the highway than my 13 Sport. How to turn an E class into an S class in 350 easy steps!!!!!!!

Darel

This was after CPO was up, everything covered under ELW.

Alandf

++1
I'm late to the thread but I find it is all tires. I am in northern California with rough roads because of rainy season traction.
I am running 18's not 19's. Staggered 245 on front 265 on rear. V rated . Really helped road noise. BTW a previous (excuse me ) BMW 535 with 19" runflats had more road noise than any car I have ever owned. Just sayin....

S-Prihadi

I think first we must understand that each driver/owner has different priority.
OP love his Michelin A/S 3+
Me in the tropics with no snow to worry, I love my Michelin Pilot Sport 4 ( not 4S, which in my country only available 19" and up )

To me tire grip in wet and dry is priority 1, and I dont like run-flat and I won't use the more extreme one , Michelin Pilot Sport Cup 2 series, coz in the rain PS4 is better.
Tire life no worry, as I would change tire per 3 years worned out or not and that is 20,000KM at best and most likely 15,000KM only.
The stickier the tire, noise is usually its best friend and low thread life is its another best friend so I have to accept my tyre of choice.
When I want lower overall cabin noise, I would do the same as OP and have fun while at it. The whole point about this make-my-car-more-silent project is also the fun and the learning process.

OP will not change his tire to a lower noise one at the cost of sacrificing the grip he loves about his A/S 3+, that I know coz i follow this thread from day 1.
So I am really following this thread with great pleasure and respect as this is the kind of content a forum should have, aside from How To Repair/troubleshoot X,Y,Z
Someone who will spent money and time to test things which will benefit all of us, intending to gain the same lowered Db.

Tom in Austin

Here in Texas they maintain asphalt streets and highways with something called 'chip seal' ... on top of perfectly good, smooth asphalt they spread oil and then finely crushed stone. The resulting coarse surface sets up a constant vibration and howling noise under your car. It can be exhausting to drive for long periods on this stuff. Thank goodness they don't do this on interstates which are such a welcome change when you get off a rural road. Where interstates are concrete, like around Houston and Dallas, there can be noisy areas but in general concrete pavement produces far less vibration and more of a soft, whirring sound from the tires.

I have test-driven a couple of S-class cars and found you almost don't notice which pavement surface you're on ... even chip-seal roads don't cause much of a fuss. That's wonderful and exactly the kind of noise reduction I'm looking for. I'm not seeking a sensory-deprivation level of quiet, rather a consistent experience where the car feels and sounds roughly the same regardless of the road you're on.

DFWdude

I've followed this thread from the beginning. I've not written much, because I've not had much to add. I think the sound levels in my E350 are fine, as is, and I fully expect conditions to change with the change in road surfaces.

If there truly is this much difference in noise between E-Class and S-Class cars, then I'm left to suspect that my E350 is nothing more than a cheap Ford Escort with a Mercedes badge on it, and I've sadly set my expectations too low.

I traded up to an E-Class because I had to put up with derision here from folks looking down their noses at my lowly C-Class... so I guess that is why I'm sensitive to it. But apparently my expectation of an E-Class (MB's best selling and most popular model for decades)... should not be all that, either.

If going to an S-Class is necessary to flip-the-switch to a quiet, luxury experience, then next time I will buy an S-Class, rather than spend the same amount of money to make an E-Class ride as quietly as an S-Class.

Sorry for the rant.

Darel

We cross-shopped a (newer) CLA and C300 vs. our E350 when we were buying. The E-class really is light years ahead of the C (especially the CLA, which felt like a Corolla knock-off).

pierrejoliat

Well, I have had them all, from my 91 190E 2.6 on, I had a 01 C240 which was a great car, I was working 45 miles away from home and really piled on the miles, rode like a small car but I think better than anything else it's size, Got my first S in 93, a 500S, Quitest S I had and awesome ride, got a 03 S500 my favorite, and an 07 S550, second favorite, So I've also had four E classes, 2002 E320, good quiet car, 12 E350 and 13 E350, love them too, there is no way an E compares to an S, they are 45K more, so one would expect an improvement in everything, but the E has most of the same options and is way easier to park, shopping and city traffic, also I stopped being a road warrior so didn't need to drive 60K a year anymore, I'm happy with the E's more garage room, less sophisticated, so less costly, better gas milage and less to insure. For a mid-size sedan, it's great. I do miss the air ride and the bank vault silence of the S.

S-Prihadi

When I first learned to drive back in early 80s, my Dad had a W126 280SE. Back then S = Carburator , SE is fuel injection, SEL fuel injection longer wheel base.
This inline 6 M110 2.8L engine from outside is ROUGH sounding ( probably the timing chain sound ), but inside it is okey. Vacuum central locking those days. Manual 5 speed, my Dad doesn't like auto.
My friend had a W126 500 SEL, auto. Damn, this 1980 - 1991 sound control technology of the 500SEL was so good and the V8 5 liter was so smooth at 240 KM/H the engine was only like 3,500 RPM or so.
240 KM/H felt and sound like 140 KM/H in my family 280SE.
That was when I grew up/studying in Singapore mid 70s to mid 80s.

Even in S class back then W126 500 SEL was so much better than the smaller displacements W126 in terms of quiteness at high speed.

Back then my dad also has a W123 280E in Indonesia/Jakarta. S class was not allowed to be imported back then, except for diplomats and state owned VIP guest cars. Poor country we were, so "luxury" items are kinda prohibited.
Comparing W123 280E vs W126 280SE, which was 100% same engine M110 I am sure, just different chassis and sound insulation level, W123 280E engine sound into cabin was MUCH HIGHER. I kid you not.
The W123 280E engine sound intrusion into cabin was almost like 1 generation older S class, the W116 280SE which my family also owned prior to W126.

But overall it makes sense. E Class W123 280E is 1976 to 1986. S-Class W116 is 1972 to 1980. S class W126 is 1980-1991
So W123 and W116 probably is still within the same sound insulation technology period.

pierrejoliat

Awesome, you are a veteran like me! My Sister-in-law is Indonesian, Her Dad and I were M-B guys, we always enjoyed talking about our old Benz"s. On occasion he would ask me to send him small accessories, I did this four or five times, he never got any of them! Just small stuff like rubber mats, ashtray inserts cigarette lighters, replacement visors, etc. He's in his mid-eighties now, so I don't see him as much, My sister is in So. Cal. for thirty years now.

S-Prihadi

By law used parts not allowed entry, crappy law.
If via USPS, probably the custom just confiscate it and dont even care to inform consignee.
If via DHL or UPS, custom will tell consignee, it is prohibited and no go.
Both proper ways NO GO.

So we have OTHER WAY of importation, when needed.

Today many are restoring W123 280E, them MB lovers.
In late 80s, I seen one hardcore bought a brand new W123 280 since day 1, never use it and hang the car by the support points.
I personally will not hang a car that long a time by the 4 support points, the chassis can get minor bending.

Our ex Minister of Technology of the late 70s Mr Habibie ( also was ex President for a while ) was a German educated kind of genius. This dude :
https://ysjournal.com/black-history-...crack-habibie/
He has the famous MB 300 SL gullwing, but the engine was the 300E from W124.
Notice I still remember how to address a W124 properly as 300E and not E300 like today


However, what I want to tell you is something unique about Habibie and MB.
He asked one of the Indonesian MB distributor to buy for him all spare parts for a 500 Coupe down to bolts and nuts, it was late 80s. So must be the W126.
Habibie told them, make a car from those spare parts. At that time I recalled the workshop manager told me that they could not get hold of the firewall, that was the last difficult bit
At that point in time late 80s, I was teaching "Mechanic English" at another MB distributor ( first importer of MB for Indonesia ), because they can't with ease find an English teacher who knows car parts in English....LOL. No google back then.
Their MB workshop was the go-to for most CD ( diplomats ) cars. So the report has to be in English for those dignitaries.
It was a short 3 months , 2 hours 3 times a week teaching and it was fun.

The funny part for me is, back then and in fact still is until today, older Indonesian uses Dutch language for car parts....which I don't understand because I started knowing car parts 100% in English .
So cross learning for me.

300+ years Indonesia was under the Dutch till 1945 independence...what da ya expect.. LOL.

Sorry if my post swing out of noise control matters

pierrejoliat

I enjoyed your post immensely, thanks for sharing! I have actually heard of Habibie, Aeronautical engineer and brilliant.

S-Prihadi

CCWW,
Take a look at this video, the NVH part, its the first few minutes. It is interesting.

ccww

Fantastic articles, thank you very much!!

My omnidirectional microphone is located vertically at the centerline of the car and held at the height and longitude of my ear which is slightly forward of the B-pillar.

It would be fascinating to explore different microphone positions, especially for the windows, which should have a strongly direction impact on the sound. I don't have the resources to acquire and use a binaural head, unfortunately. The first article's points are excellent, there is much more than simple dB measurements. I think that 1/3-octave band is still much better than an overall figure, but clearly not as revealing as their masked and directional measurements. This certainly leaves a place for subjective impressions along with measurement in my project. I think that it is very important to acknowledge, as explained by masking in the first article, that reducing sounds in one frequency band or direction will impact the perception of other noise. Unfortunately this makes the project a little like whack-a-mole, but I think that in the specific case of the W212 we're helped by the fact that much of the car, like the front of the cabin, has excellent acoustics while the rear seat area is quite poor. This means that simpler modifications may have greater overall effects.

The second article has some great information about the nature of vehicle noise and what frequencies are impactful. Like I've observed in the W212, tire noise is the overwhelming contributor to overall NVH at speed. The article claims that most of the annoyance comes around 50Hz - 200Hz, which is surprising to me considering the relatively low frequency and low sensitivity of human hearing at those frequencies, although as shown by my measurements, the unweighted amplitude can be very high at those frequencies. The second article also supports the great importance of tires, as pointed out by many posters. I've never disputed this, but a big reason for this project is for me to have my cake and eat it too: I want ultra-high performance all-season tires and quiet!

ccww

Thanks very much for the kind words. Hopefully by the end of this project I will have some useful empirical suggestions for those who do want to make their W212s quieter!

Did you notice any substantial difference from these modifications? With respect to the second article posted previously by @S-Prihadi all of these modifications should solely address structure-borne noise, which is a substantial contributor to overall NVH and not readily addressable by absorption or blocking. Interested to know if it did anything for you.

ccww

You're absolutely correct, I want both the good tires and less noise! Only time and more measurements will tell if I can have my cake and eat it too!

ccww

Your subjective goals align very much with mine. I'm not hoping for S-Class levels of sound deadening, if I was I would be looking to purchase one instead. But the E250 BT is by far the more practical choice for my > 40,000 miles per year of highway driving. I primarily want less of a dramatic harshness in noise on certain stretches of poor road on my regular routes.

ccww

Very interesting to see how Tesla does things. That TPO is pretty cool stuff! I've never seen an aftermarket version, but if anybody has a source I'd be intrigued! Otherwise hopefully the constrained-layer butyl rubber and aluminum foil will serve the same purpose of damping.

retna7

Front Door. Mass Loaded Vinyl. Crossover. 3M tape. Rivnuts.

Rear door. Steel Braided wire shroud. Plastic grommets. Valerian steel drill bits. Speaker wire from crossover in door to mids on rear deck (component speakers). 16 gauge wire.

Front door panel, NVX sound deadening, lubricated window regulator, foam speaker ring, 6.5 inch speaker with adaptor.