Fredff

Driving a c200 amg line 2016. Have a resonant booming sound from drivers foot well. Starts at 15mph on smooth road resonants at 30 MPH and continues at various levels at higher speeds. Influenced by road surface so suspect it is driven by a component of road noise.

ManiacGT

Same car, same noise.

do you have airmatic?
what size of wheel? (18/19")
what brand of tyre?

Fredff

18 inch and Continental. Noise could also be described as a buzz ! Local dealer has tried and failed to minimise. Normal suspension. I suspect that the front speaker resonamce chambers culd be involved since the sound seems to be a fixed frequency and fairly pure. Unlike normal road noise which varies according to speed and road surface conditions.

ManiacGT

my car is 19" runflats with airmatic. My chief suspect is the runflats . I'd describe the noise as a howl/drone/hum, hitting rough ground and imperfections make the noise louder like a deep version of the sound you get when you tap an inflated balloon. Much better at low speed. Pitch remains the same once it starts. Hence thinking tyres (or air suspension but you've now discounted that for me).

there have been other reports of similar on here and I read elsewhere this has been cured by other people removing the continental tyre and replacing with the likes of Pirelli.

Fredff

Thanks for your interest in this item. I have been working at it for a couple of months. The local dealer has been very cooperative but I am surprised that they do not have more info on this. I have driven a c class diesel and a b class diesel as courtesy cars and I can detect the same noise on both but at a much lower level.
Once you tune into this noise you can detect from about 15mph on very smooth road surface and then on up. The level of noise does change with speed and road surface but always sounds the same. It is possible to isolate this noise from the other noises in the cabin including road noises. The noise also is generated inside the cabin and is not coming from outside the car.
The common feature in my experience for this noise has been the bass speaker resonance chambers. Just a theory.

removedCFGaccount

So it is likely sympathetic vibration?

Mike5215

I know when we did the Audison upgrade on the Burmester we got these random bursts of boomy bass that I hadn't heard before. We traced it back to the Vehicle Noise Compensation circuit in the Burmester getting confused and compensating for stuff that didn't need compensation.

Does the noise stop if you shut down COMAND?

Fredff

I have an electronic engineering backround but thermionic valves were in use in my university days so no recommendation there - just makes me inquisitive.
My theory is that a component of the vibration which occurs between the road and the wheels is transmitted into the front bass resonance chambers and finds a resonance. This produces a clean resonance frequency which is audible in the cabin.I describe it as a buzz or drone or boom since it is very subjective. This vibration component remains at various road speeds and surface conditions but various types of road noise will be audible from outside the cabin. These noises are superimposed on this basic noise which can still be isolated by the human ear. Just a theory and welcome any comments to completely ditch it !!

ManiacGT

There is another post on here with a video showing this. I can't find it despite trying but I've seen it and it examples the noise well.

Mike5215

Yeah I'd like to hear it. I tried a YouTube search but no luck...

Fredff

I would also like to hear this It is such a characteristic sound it would be easy to identify.

Gungaslow

Does it kind of sound like a wet polar bear fart by any chance?

removedCFGaccount

Ha, ha!

ManiacGT

I tried recordIng the noise (the droning, not the fart) and just got hiss from road noise. I'll keep trying to find the original road noise post.

ManiacGT

Meh, I found the post but the video has been removed

https://mbworld.org/forums/c-class-w...e-problem.html

Mike5215

Technically if its consistency can be described as "wet", it's more than just a fart. I believe the medical term is "shart".

removedCFGaccount

I hear the dime....

dieseldoc

Agreed. Usually makes a big mess. Code brown!

Fredff

Hi Maniac GT. Thanks for the post reference. A lot of info there. Pity the Video was removed. Nice to know I am not the only wierdo listening to noises instesd of driving !

auditoamg

Code brown, definitely worse than a code yellow.

Says the two of us who clearly have a medical background (or know someone).

dieseldoc

ManiacGT

by quite a margin

dieseldoc

Sorry!

removedCFGaccount

A haiku:

Senescence, the docs.

A Polar bear cerebrates.

D. Doc fulminates.

Anyway, it is likely some kind of sympathetic vibration.

dieseldoc

.