Measuring sound level at freeway speeds

[Kyiv]

Today I measured how loud my 400E (16 inch MB eight hole wheels, 215/55 continental all season performance tires), a/c off, while driving a steady 82 mph with my phone and an app. Measurement bounced between 68 and 71db. I'd say it was mostly 70db. It's understood that this is not a scientifically accurate figure.

Anyone else measured their car? What was the result (on what wheels/tires)?

 

[500AMM]

I have never checked the noise level, but yes, the 124 is pretty noisy inside. I find the wheel noise to be the most dominating and it increases rapidly around 80 kmh, have to start talking louder to the passengers. The wheel noise do also vary with wheel size, tire type and road surface conditions.

Could be done something with this, but one thing is to put sound barriers inside the entire cabin, on the backside of the door skins etc.. and spray something inside the wheel wells, but it is several hollow sections which carry the noise as well. The channels under the doors, the roof/door frame members and I think it is hollow sections behind the back seat rest bolsters - in front of the lower part of the wheel wells. It is also hollow sections in the sides in the front foot well, behind the plastic trim. None of these have any proper sound barriers but could be filled with foam or expandable spray foam, but I wouldn't use spray foam in all places due to work on the car at a later point.

10 dB increase sounds like a doubling of the noise level, and the opposite on reduction. But I guess which frequency or type of noise may be more important.

 

[TerryA]

@gsxr, Dave, It’s time to show your DynaMat pics again. Did it reduce the noise level any?

 

[gsxr]

@gsxr, Dave, It’s time to show your DynaMat pics again. Did it reduce the noise level any?

Subjectively, yes, it did reduce cabin noise a little. But I had no way to measure dB's before & after so I can't quantify the results.

 

[Jlaa]

Today I measured how loud my 400E (16 inch MB eight hole wheels, 215/55 continental all season performance tires), a/c off, while driving a steady 82 mph with my phone and an app. Measurement bounced between 68 and 71db. I'd say it was mostly 70db. It's understood that this is not a scientifically accurate figure.

Anyone else measured their car? What was the result (on what wheels/tires)?

I have never checked the noise level, but yes, the 124 is pretty noisy inside. I
1 dB increase sounds like a doubling of the noise level, and the opposite on reduction. But I guess which frequncy or type of noise may be more important.

Wow, I feel the 036 is very quiet inside. Maybe my reference of comparison is off. Compared to a 2021 Toyota Venza, which is kinda like a “Lite” Lexus NX, I find the w124.036 v comparable in wind noise, tire noise, etc.

I feel like a spectral plot to see noise energy across all frequencies is perhaps a better gauge for noise …. To discern what kind of noise one is hearing. 10 dB increase is a perceived doubling of noise since it is on a logarithmic scale.

 

[kegmankipp]

I put a case of 10 sheets of Dynamat Xtreme on the doors, inner and outer skins, on deep wells on floors, under and behind rear seat, under rear shelf and on the parts of wheel wells I could access. Took a day but we’ll worth it.

I measured a 4db drop, via my SPL meter that was set for A weight and slow response.

Noise used to come evenly from all around. Now the noise from below the windows dropped so much that now the wind noise around windows is much more noticeable. But I’d Dynamat it again in a heartbeat as it makes the car much more enjoyable.

 

[socal210]

I agree with Jlaa, 124s are very quiet cars even by modern standards. That being said my cabriolet is a very quiet car but does have some noticeable wind noise coming from the canvas top. Still much quieter than my Truck by far.

 

[Kyiv]

I measured a 4db drop, via my SPL meter that was set for A weight and slow response.

Do you remember from what to what figure?

 

[500AMM]

Wow, I feel the 036 is very quiet inside. Maybe my reference of comparison is off. Compared to a 2021 Toyota Venza, which is kinda like a “Lite” Lexus NX, I find the w124.036 v comparable in wind noise, tire noise, etc.

I feel like a spectral plot to see noise energy across all frequencies is perhaps a better gauge for noise …. To discern what kind of noise one is hearing. 10 dB increase is a perceived doubling of noise since it is on a logarithmic scale.

It should be 10 dB of course, misprint corrected in my previous post, thanks!

 

[TerryA]

Subjectively, yes, it did reduce cabin noise a little. But I had no way to measure dB's before & after so I can't quantify the results.

I had no complaints when I had the stock muffler and resonator on my car I was perfectly happy with the noise level. However, I switched out that for a TV Y-Pipe and RennTech back box. Then the noise was pretty loud inside the car.

I haven’t tried DynaMatt yet but I have installed a sheet of sound rated drywall under my trunk carpet along with stuffing batt insulation around the fuel tank and behind the trunk fender covers.

I have since removed the Y-Pipe in favor of a straight thru Magnaflow SS Camero muffler fitted into the stock resonator pipes so it bolts up into the stock location.

My latest setup makes inside the car sound OK but at certain speeds it still makes some noise but bearable.

One thing that I think might help is under the car where the resonator cavity is would be to fill it with sound insulation and cover it with sheet metal. I think the resonator cavity traps noise from the straight thru exhaust system.

Anyway, that’s my story and I’m sticking w/ it.

PS: Before my car sat for 3+ years the noise didn’t bother me as much. But I have been driving a stock KIA for the last 60K miles which is pretty quiet. Stepping back into the 500E was kind of a shock to my system I guess

lol

 

[kegmankipp]

Do you remember from what to what figure?

I don’t remember but I’ll retest as I still have my vintage SPL meter. Give me a day or two

4 db drop was at 70 mph.