Tyre Cavity Noise: Mercedes C200 v Nissan Qashqai

[classcchap]

It's very easy to make a car quiet and relatively easy to make a car go round corners. The problems come when you expect it to do both.

If I’d wanted a car that went round corners I’d have bought a beemer.
I wanted a car that was quiet - that’s why I bought Mercedes.
And yes, I AM living with the consequences, my purpose now is to warn others.

 

[markjay]

Had a hard time finding my current W204.

I was looking for an Executive SE because I wanted a high comfortable ride (not lowered) with soft (not stiffened) suspension, and 16" wheels (not 17" or 18").

You would have thought 'run-of-the-mill'....not so. Most second hand cars on offer were of the 'Sport' variety, with lowered stiffened suspension, side-skirts and rear diffuser, front spoilers etc, not to mention the obligatory bing wheels.

But the good news is that I did eventually manage to find my soft-sprung comfi-barge unmodified Executive SE

 

[MercedesDriver]

If I’d wanted a car that went round corners I’d have bought a beemer.
I wanted a car that was quiet - that’s why I bought Mercedes.
And yes, I AM living with the consequences, my purpose now is to warn others.

Beemer is for straight line driving, Audi for cornering, Alfa for admiring while parked and Mercedes for all three. You’ve made a good choice.

 

[Gbrowncls55]

I don't pretend to understand half of the above, but quietness is the prime consideration for me when buying tyres as there is both a statistical difference (tyre markings) and a real noticeable difference in tyre noise (TCN?) between brands. After much investigation and trial I have found Dunlop Maxx Rt and Goodyear F1 Assymetric 3s to be the quietest (and by some margin) without sacrificing grip (unless perhaps you are on a track). I was also told that MO rated tyres used a more comfortable compound but no idea if that's true.

 

[classcchap]

It does seem almost unbelievable that Mercedes have not studied frequency analysis findings from a W205 during it's development.
The amplitude of the TCN is way above what I would be considered normal road noise.
My suggestion is that either there is a specific fault with a number of cars, or the sign off team made a conscious decision that it was within the realm of what most people would term acceptable. This really seems unlikely given the importance of this global model for Mercedes!

That’s just what I thought. I too thought mercedes couldn’t possibly release a car like this but they have. The CEO has seen what you have seen and says it normal. Think about it - why wouldn’t they fix it if they could? They can’t fix it because that’s how the C Class is. Stop looking for some oddball reason. My best guess is they underspecified the wheel bearing, to lower rolling resistance and unsprung mass - all good reasons - but the primary roll of the wheel bearing is to stop the wheel thrashing about. Oops.
Regarding wanting to see TCN recordings, I’m preparing an instructional so you can do your own tests, then I can post my files and you can see exactly what I’ve found. Hey we’d be able to swop files that would be good.

 

[190]

I wouldn't entirely rule out MB making a compromise on noise levels if there was some other competing reason. They did it with direct injection which is noisier than port injection. The competing reason being emissions and headline MPG figures.

 

[st13phil]

That’s just what I thought. I too thought mercedes couldn’t possibly release a car like this but they have. The CEO has seen what you have seen and says it normal. Think about it - why wouldn’t they fix it if they could? They can’t fix it because that’s how the C Class is.

While not denying that you have a problem with your car, I can honestly say that I've never noticed intrusive TCN in any of the W205's I've driven, which includes a couple of 220d saloons, a 300h estate, a 220d cabriolet and a C63S saloon. Maybe I'm just not sensitive to it, or maybe it's not a fault of type (as you believe), rather one of example?

If it were the general problem you suggest it to be, surely the internet would be full of complaints? Yet a quick google search doesn't really turn up anything significant (try searching for "Mercedes crabbing" for a comparison). Ironically, one thing that a search for "C Class Tyre Noise" did turn up was an Evo review from March 2017 which notes that:

The ride is generally supple even on the worst of road surfaces, while wind and tyre noise are suitably suppressed. This makes the Mercedes comfortably the best car for relaxed driving in its class, beating the BMW 3-series, the Audi A4, the Jaguar XE and the Alfa Romeo Giulia.

(my emphasis).

I'm genuinely interested to see if another W205 owner can carry out tests on their car to see if it exhibits what you are experiencing with yours, so will continue to watch this thread.

 

[Mactech]

My best guess is they underspecified the wheel bearing, to lower rolling resistance and unsprung mass - all good reasons - but the primary roll of the wheel bearing is to stop the wheel thrashing about. Oops.
Regarding wanting to see TCN recordings, I’m preparing an instructional so you can do your own tests, then I can post my files and you can see exactly what I’ve found. Hey we’d be able to swop files that would be good.

Well, I'm very familiar with doing installation stiffness tests on wheel bearings and upright assemblies,(mostly on race cars ) but never chased NVH through that load path...but every day is a schoolday and intrigued to find out what happens!

We just need to find a happy W205 owner to replicate your tests.

 

[ManiacGT]

My C200 petrol estate with AirMatic has this noise (run flats) (S205)

Way louder than my BMW. It’s a howling noise from th tyres and differs by weather and temp, starting as stated above 10/15 mph.

I’ve had people in the car that can’t hear it. To me it’s the main noise I hear.

 

[grober]

I'm guessing its something to do with this company?
Bay Systems Ltd
Bay Systems Ltd
http://www.baysystems.ltd.uk/documents/TCM v6.pdf

and this article
Web Exclusives : Tire Technology International
I was particularly interested in this paragraph
In-vehicle noise
Vehicles propelled by electric motors have no combustion noise to mask road and tire noise. Should the trend towards lighter structures and deteriorating road surfaces continue, then road and tire noise will become ever more apparent to the occupants of the vehicle. Reduction in road and tire noise, particularly for speeds < 50km/h, is likely to become a focus for both tire and vehicle manufacturers over the next 10 years.


In-vehicle noise (cabin) levels associated with tires will be made up of two principal components: firstly, the primary tire cavity mode and possibly other resonance effects of tire and wheel; plus the tread noise exciting a response in the vehicle structure and airborne transmission.


The TCM data can be successfully correlated with microphones positioned within the cabin to reveal when and how tire noise enters the cabin. Initial research indicates that the phase of the primary cavity resonance within each of the four tires has an important bearing on the level measured in the cabin.

In other words the noise generated by the tyres in both vehicles might be of the same order of magnitude but that noise is transmitted to the passenger compartment more efficiently in the Mercedes. I have speculated about the difference between hydraulic and electric powered steering but another factor might be the extensive use of alloy in the body construction of the W205.

New Mercedes C-class technical details shown | Autocar

 

[classcchap]

Well, I'm very familiar with doing installation stiffness tests on wheel bearings and upright assemblies ... and intrigued to find out what happens!

We just need to find a happy W205 owner to replicate your tests.

I value your input, Sir, and if any W205 owner can get to Sodbury, I’d be very pleased to run a test, that would be good.
I ran another test this morning, in prep for instructional, saw 12dB - it’s very repeatable.

 

[classcchap]

My C200 petrol estate with AirMatic has this noise ... starting as stated above 10/15 mph.

I’ve had people in the car that can’t hear it. To me it’s the main noise I hear.

A fellow traveller (as it were), I can’t tell you how pleased I was to read you post. This is the ONLY car I’ve heard it in and it is by far the loudest noise.

 

[classcchap]

...the noise generated by the tyres is transmitted to the passenger compartment more efficiently in the Mercedes ... another factor might be the extensive use of alloy in the body construction of the W205.

Yes grober, I think you’re on to it now. I also don’t see any reason to think it’s restricted to C Class.

 

[grober]

17 minutes in

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And a trade journal describing newer methods of body construction[ bonding and riveting] in the new generation of vehicles
WHO WILL SUPPORT THE NEW VEHICLE? | Automobile Magazine | Automotive Refinisher

 

[st13phil]

It would be very interesting to find a local W205 owner who has no perceived issue with their car and put it through the same test.
Any takers?

OK, I know we're a couple of weeks on but I had a loan W205 C220d Premium this week and £8 burning a hole in my pocket so I installed SpectrumViewPlus on my iPhone 8 Plus and recorded a run along a bit of road at a constant 55mph. This was different to the OP's scenario in which he coasted down from 50mph (presumably in neutral?) and I was using a different recording device too, so the results aren't directly comparable. For good measure, I repeated the same test in my W212 E63. Same road, same constant 55mph. My capture device mounting was not as sophisticated as the OP's: I just laid the iPhone on a rolled up coat on the passenger seat, with the mic pointing forwards.

This is a shot of the resulting Spectrum Analysis:

C220d Vs E63

• st13phil
• Feb 16, 2018

C220d in yellow; E63 Biturbo in blue

The yellow trace is the C220d, while the solid blue trace is my E63 Biturbo. Several things stand out:

1. The 220Hz peak in the C220d's plot matches that identified by the OP. I said in earlier posts that it was not something I'd noticed in all the W205's I've driven, and this car was no exception, so maybe I'm just not sensitive to it in the same way as the OP, or...
2. Maybe I don't notice the TCN noise because it's dwarfed by the much louder low-frequency components when driving (rather than coasting)?
3. There is massively less low-frequency noise in the E63 Biturbo's cabin. In fact, although in measurement terms it's quieter over much of the frequency band displayed, the perception when driving is that it's not that much quieter in cruise - perhaps because the noise levels between the two cars are similar at around 3kHz where the human ear is most sensitive?
4. If you look carefully, there is a modest peak in the E63's plot at around 220Hz, but I don't hear that either

Not sure how much light this has shed on anything, but it was a fun way to idle away a few minutes.

 

[grober]

There is this contemporary thread on W205 wind noise?
W205/ S205 Wind Noise?

 

[Mactech]

OK, I know we're a couple of weeks on but I had a loan W205 C220d Premium this week and £8 burning a hole in my pocket so I installed SpectrumViewPlus on my iPhone 8 Plus and recorded a run along a bit of road at a constant 55mph. This was different to the OP's scenario in which he coasted down from 50mph (presumably in neutral?) and I was using a different recording device too, so the results aren't directly comparable. For good measure, I repeated the same test in my W212 E63. Same road, same constant 55mph. My capture device mounting was not as sophisticated as the OP's: I just laid the iPhone on a rolled up coat on the passenger seat, with the mic pointing forwards.

This is a shot of the resulting Spectrum Analysis:

C220d Vs E63

• st13phil
• Feb 16, 2018

C220d in yellow; E63 Biturbo in blue

The yellow trace is the C220d, while the solid blue trace is my E63 Biturbo. Several things stand out:

1. The 220Hz peak in the C220d's plot matches that identified by the OP. I said in earlier posts that it was not something I'd noticed in all the W205's I've driven, and this car was no exception, so maybe I'm just not sensitive to it in the same way as the OP, or...
2. Maybe I don't notice the TCN noise because it's dwarfed by the much louder low-frequency components when driving (rather than coasting)?
3. There is massively less low-frequency noise in the E63 Biturbo's cabin. In fact, although in measurement terms it's quieter over much of the frequency band displayed, the perception when driving is that it's not that much quieter in cruise - perhaps because the noise levels between the two cars are similar at around 3kHz where the human ear is most sensitive?
4. If you look carefully, there is a modest peak in the E63's plot at around 220Hz, but I don't hear that either

Not sure how much light this has shed on anything, but it was a fun way to idle away a few minutes.

Thanks for this and very interesting.
As a sound engineer turned automotive engineer, I have long been aware that the quality of noise is often much more important than frequencies and decibels.
The noise quality is easy to spot but very hard to measure and quantify. The Audiophile and top end of the Hifi business has worked on this principle for years. The human ear is the best judge of what is a pleasant sound and what is annoying....and we are all slightly different!
Ford coined 'NVH' many years ago and it is made up of 3 distinct elements Noise, harshness and vibration....but they all come together to create the environment we either love or hate.
In recent years I have got into hi-res audio and now find many CD quality tunes 'harsh and spikey' despite exactly the same volume and frequencies.
This a very big subject, and because of the human element, is always going to be......well subjective!

 

[grober]

Maybe Mercedes should be offering Vehicle Noise Cancellation systems as an option in future on all their models ? I don't know just how effective these systems are at present but could be part of the solution? Should be relatively easy to implement since the distributed output sound system is already there in the form of ICE transponders?
HALOsonic - Active Noise Management Solutions

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[whitenemesis]

Cars generally are far far quieter now than in my youth but is this really a ''good' thing? Great for the chauffeured few but as a driver one has become very detached from the experience. Cocooned in one's own little world. Young drivers seem easily distracted buy their tunes, phone, passengers. Before they know it they're speeding, or drifting across the lanes.
Perhaps this detachment explains the popularity of noisy aftermarket exhausts, the harsher, sporty suspension, at least for those who love to drive?

Back in the 70's travelling at 60mph in the average car was a raucous, white knuckle experience. As a driver one was very much 'in tune' with the job in hand.

 

[rockits]

I have an old C class , all I can hear is the V8 engine in front of me and the Quad exhaust behind me .

Agree with that....buy a V8....problem. solved [emoji6]