Tyre Cavity Noise: Mercedes C200 v Nissan Qashqai

[classcchap]

I think it’s time to talk about Tyre Cavity Noise. You will have heard it even if you’ve not heard much about it.

To kick off have a look at this:

The spike at the centre is tyre cavity noise and, in case you’re wondering, up is loud - so it is by far and away the loudest noise in the cabin. That’s Mercedes-Benz.

Nissans Qashqai - same conditions, same location - looks like this:

I find this quite shocking and I for one will not be buying another Mercedes-Benz.

Like I said, I think it’s time to talk about this and, if there is any interest I can show you how to test your own car - chances are you’re holding all the tools you need right now.

 

[merc85]

Our Qashqai was a terrible car, They couldn't even weld the Tailgate on straight when they made it, It had to go back to Nissan for it tobe re-welded lol The Sack of spuds (65) Reg X-trail we bought is going Rusty along the roof and around the door rubbers, Not to mention the random miss fire from cold which Nissan has tried to fix but cant. Terrible car's and terrible service. The X-trail was 28k! Cant wait for it togo back very soon.

 

[Crickleymal]

So what is tyre cavity noise? Resonance within the tyre?

 

[NigelOB]

I think it’s time to talk about Tyre Cavity Noise. You will have heard it even if you’ve not heard much about it.

To kick off have a look at this:

The spike at the centre is tyre cavity noise and, in case you’re wondering, up is loud - so it is by far and away the loudest noise in the cabin. That’s Mercedes-Benz.

Nissans Qashqai - same conditions, same location - looks like this:

I find this quite shocking and I for one will not be buying another Mercedes-Benz.

Like I said, I think it’s time to talk about this and, if there is any interest I can show you how to test your own car - chances are you’re holding all the tools you need right now.

There a lot more factors to take into consideration such as, tyre make, type, size, suspension setup etc. Not to mention weather and conditions.. the spike looks more like the cars hit a pot hot or similar.


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[Dippo]

Why is one at 35 mph and the other at 30 mph if you're trying to compare them?

 

[classcchap]

So what is tyre cavity noise? Resonance within the tyre?

Yes, exactly that. The ‘doughnut’ of air inside the tyre rings like a bell at its characteristic frequency - it contains a lot of energy which then comes in via the suspension producing a single clear note. In this case, as you can see, my C200 produces 220Hz which is the ‘A’ below middle C for those musically inclined. It’s very loud, again, as you can see, and it drives me bonkers.

Here’s a nice Loughborough University PDF if you’d like to know more:

https://dspace.lboro.ac.uk/dspace-jspui/bitstream/2134/22561/1/DJO-InterNoise2016_V5.pdf

 

[grober]

So what is tyre cavity noise? Resonance within the tyre?

Its a wheel +tyre air cavity resonant frequency/s set up by excitation caused by the interaction of the tyre tread and road surface- main direction being circumferential. It used to be called tyre noise or road rumble but tyre cavity noise is a more up to date description. TCN is only going to be partly influenced by vehicle manufacturer. Far more by tyre tread pattern, sidewall stiffness and inflation pressure. Unless the quashqai was running the exact same tyres at the same inflation pressure as the C class the signicance of any comparison would surely be in question? These resonant frequencies can be damped down by suitable internal absobers.

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I imagine that todays low profile tyres and routinely higher inflation pressures [ to reduce rolling resistance ] don't help either!

 

[NigelOB]

And different days


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[whitenemesis]

My Lexus was advertised as having acoustically damped rims. Any information that might support that?

 

[Deleted member 65149]

Why is one at 35 mph and the other at 30 mph if you're trying to compare them?

Because the Qashqai is too noisy to drive above 30mph?

 

[Mactech]

Whilst I agree there is a spike in the noise frequency which is fairly typical of internal tyre resonance, you will also note that the majority of noise is under -48 in the Mercedes at 35mph and much above that in the Nissan at 30mph!
Without knowing the tyre type, size, make and pressure and more importantly the actual surface the cars are running on the two snapshots are not directly comparable.
I also agree that tyre cavity noise is a huge problem in most cars now, specifically because all other noise is well subdued....as shown in the Mercedes trace.

 

[brucemillar]

As said by many above. The make up of the tyre/manufacture and design contribute a vast amount to this noise.

To get to anything close to blaming the car you would have see so many comparisons your head would melt. It simply is not "apples with apples"

To name a few:

Road Surface
Surface Temperature
Surface make up
Surface Condition
Wet or Dry
Contaminants

Tyre Brand
Design
Make Up
Pressure
Cornering forces (or not)
Downforce
Lift
Turbulence

Or just sit in the car. My AMG on Pirelli's was the equivalent of driving inside an empty oil drum with steel wheels = horrendous. On Falcons? Lovely.

 

[Mactech]

Couple of other factors which have significant effect on this issue are depth of tread, and therefore the mass of the tread of the tyre which has huge effect on the damping the resonance, and Airmatic.
One of the often unsung attributes of air suspension is the isolation of the noise path from the tyre to the car, which is why almost all of my recent cars have had this feature.

 

[merc85]

Because the Qashqai is too noisy to drive above 30mph?

Or probably in LIMP mode

 

[classcchap]

Whilst I agree there is a spike in the noise frequency which is fairly typical of internal tyre resonance, you will also note that the majority of noise is under -48 in the Mercedes at 35mph and much above that in the Nissan at 30mph!
Without knowing the tyre type, size, make and pressure and more importantly the actual surface the cars are running on the two snapshots are not directly comparable.

Oh yes, of course the majority of noise in the Mercedes is less - that’s why I bought it. That isn’t the issue. It’s the cavity noise which, in the Mercedes-Benz is very much louder than the Nissan. If I’d known that I’d never have bought one and, as I said, I won’t be buying another.
As for tyre pressures, they were set i.a.w. the handbook prior to test and road conditions were the same and it was the same stretch of road. The snapshots show the highest peak recorded in each case.

BTW I’m not carrying a torch for Nissan - it was just

 

[Mactech]

Well I would be looking at the source of the noise and not the car. I think you would agree that a set of tyres is going to be a great deal cheaper than a car swap.
What is the current tread depth? Are they Continentals?
I have seen some huge changes in different tyres as Bruce Millar has eluded to.

 

[Eddy77]

My CLK is super quiet. My Mondeo is wAaaaaaaay louder. Both run 18” rims on low profile rubber. I think the MB has better sound proofing. But a lot depends on tyre brand and pattern. Mondeo runs Uniroyal rain sports....Mercedes is on Avon ZZ5s

 

[classcchap]

Well I would be looking at the source of the noise and not the car. I think you would agree that a set of tyres is going to be a great deal cheaper than a car swap.
What is the current tread depth? Are they Continentals?

The noise was present within a 100 yds or so from delivery, at that time I had no idea what it was - it sounded like a prop shaft on the way out. On every journey it begins at about 15 mph and stays until walking pace. As far as tyres go it was delivered from Benz on Continentals, the vendor swapped them for Goodyear’s - I’ve recorded the highest peak on Goodyear’s. Nothing to do with treads or brand or pressures or roads or anything else - it’s a suspension fault.
Clearly I can’t control for every variable - that’s just stupid - the bottom line is that I should not be able to produce these graphs at all nor would I be motivated to - if there was not a very serious problem with the C200.
BTW I am aware of what the tyre makers are up to and polyurethane tread backing is only good for 6dB at most - my C200 creates 18dB.

 

[grober]

Does pose some interesting questions tho. Manufacturers now offer a wide range of wheel and tyres sizes on their new cars. Should we assume that each of those are all tested /optimised during vehicle chassis testing/development or do they optimise on one particular suspension/wheel/tyre combination and "wing it " a bit on the rest ? If so that would be the one to go for if we could only find out which one that was.

 

[classcchap]

My CLK is super quiet. My Mondeo is wAaaaaaaay louder. Both run 18” rims on low profile rubber. I think the MB has better sound proofing. But a lot depends on tyre brand and pattern. Mondeo runs Uniroyal rain sports....Mercedes is on Avon ZZ5s

I’m very pleased for you eddy - that’s lovely.