W204 vs W207 noise assessment

[cinek]

Yesterday's discussion got me thinking, is there really a difference in internal noise between C Estate and E Coupe?

Two subjects tested were:

E 350 Cdi Sport Coupe (auto)

and

C 220 Cdi Estate Sport Plus (manual)

The journey was covering exactly same route, starting at 30mph single, then 40mph dual, 70mph motorway, back to 40mph dual and lastly 30mph single. All in all, about 11 miles in total.

Windows up, music turned off, no harsh accelerating just plodding along.


Here are the results:

W207 Coupe




Average 66.1dB






W204 Estate



Average 68.1dB

Although there is a difference (+/- 2dB), it would be pretty much unnoticeable to a human ear, so my previous statement about estate sounding lot louder is clearly wrong

 

[whitenemesis]

Could the frequency of the noise make one seem "more noisy" than the other?

 

[cinek]

Could the frequency of the noise make one seem "more noisy" than the other?

Possibly, there is also the 'content factor' to be considered.

The estate was completely empty at the time of the test, no loose items, nothing in the cab/back.

The coupe on the other hand, had a large child seat (non ISOFIX), another seat booster and some toys in the back which all together did make a rather annoying racket during driving.

 

[st13phil]

Interesting experiment, thanks for sharing it.

My experience of my W212 vs the W204 that I used to own is that under cruise or moderate acceleration the perceived noise levels were fairly similar, with the W204 being slightly louder. This would correlate with the +2dB average difference you measured. However I would suggest that most people don't use the average under cruise as their sole criteria when describing one car as being noisier than another, instead also factoring in peak noise levels under hard acceleration. Of course, the noise "signature" is also important in perception of noise, as mentioned by whitenemesis. How many times have you heard the description "sounds a bit gruff when pressed" about the 4-pot MB diesels?

It would be interesting to do a further test, accelerating on full throttle in both cars and looking at the peak noise level in each. I would suspect that the difference is more than the 2dB delta from the first experiment, but it would be useful to quantify it.

 

[cinek]

It would be interesting to do a further test, accelerating on full throttle in both cars and looking at the peak noise level in each. I would suspect that the difference is more than the 2dB delta from the first experiment, but it would be useful to quantify it.

Will look into it when get a chance again.
Acceleration noise will be no doubt much higher than 2dB compering V6 to gruff V4.

 

[grober]

It should perhaps be pointed out that decibels are a logarithmic unit. This means that a 3 dB difference means a sound that twice as loud. Decibel - Wikipedia, the free encyclopedia The human ear is also more sensitive to certain frequencies 2-4 Khz and this will also vary with age. I assume the dB meter was" listening " to the full audio frequency which again might be in contrast to the what the driver's ear might experience as others have alluded to. Tricky business this noise thing! Personally I have found that the V6 diesel is noticeably quieter- especially under hard acceleration. There are however lots of factors to be taken into consideration. For example I have found diesel fuels with a higher cetane rating will quieten down the OM651- not by much but perceptible and in the estate running with the luggage cover "deployed" reduces rear road and exhaust noise. Thanks for taking the trouble to post those figures.

 

[blue gnome123]

Also just to be pernickety - isn't the W207 built on a W204 chassis? Maybe a c-class estate vs e class estate would be a better comparison?

 

[cinek]

Also just to be pernickety - isn't the W207 built on a W204 chassis?

Not as far as I know.

 

[blue gnome123]

The Mercedes E-class coupe (W207) shares its platform with the C-class.

from Mercedes-Benz C-Class - Wikipedia, the free encyclopedia

and http://www.autoblog.com/2009/05/19/2010-mercedes-benz-e-class-coupe-a-c-class-underneath/

 

[grober]

It sort of depends on how you define chassis. In fact the W204 C class and W207 E class Coupe do share the same platform--- wheelbase and track-- no doubt with recalibrated suspension elements to compensate for any changes in body weight--if any.
Mercedes were a bit naughty with this one as the the rest of the W212 E class range saloon estate have both a wider track and longer wheelbase and are noticeably bigger cars when viewed together.

 

[cinek]

Well, they do say you learn every day...

 

[Dieselman]

Also just to be pernickety - isn't the W207 built on a W204 chassis? Maybe a c-class estate vs e class estate would be a better comparison?

I thought he wanted to compare two C class cars, one being the E coupe (C class in drag) and the other the estate.
I thought it made a good comparison.

As grober pointed out, the noise is 66% louder in the estate.

The original question related to the quality of sound in both cars. The smaller more acoustic Coupe will always sound better than a longer, open estate.

 

[V12]

And despite what they say, they don't share the same sound system.

MB generally use an infinite baffle setup in all the coupe and saloon cars which produces a much smoother frequency response and blends effortlessly with the door speakers.

An estate car always uses a 'sub box' which is used to try and make the speaker as efficient as possible in as small a space as possible. This inevitably leads to dips and peaks in the frequency response which has a knock on effect in how the whole system interacts.

Add to this that the coupe only has one set of tweeters up front where as the estate cars have a second set in the back doors which will also mess with the focus and sound stage.

Then you have the acoustic environment which is another major factor, as you've already covered.

In summary, All cars are a compromised environment but estate cars just totally suck for sound system.

 

[cinek]

...estate cars just totally suck for sound system.

Amen to that