Wind Noise Detection/Follow on

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Steve Smith
Pico Staff Member
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Joined: Sun Aug 25, 2013 7:22 am

Wind Noise Detection/Follow on

Post by Steve Smith »

Following on from the forum posts below (thinking about cabin leakages):
post50851.html#p50851 where I touched upon……….

“The Function Generator can be used to playback very high frequencies via the In Car Audio System whilst searching for cabin air leaks or wind noise.

Playing back a fixed high frequency audio signal (around 20 kHz) whilst using the NVH Mic to “Sniff” about the vehicle exterior trim and monitoring the frequency display for high amplitudes at 20 kHz will indicate the source of the cabin air leak.”

And………, topic21710.html (using ultrasound)

Thanks to discussions with colleagues and delegates it occurred to me we could also use a Smart Phone to act as a squawker inside the cabin.

Using a Tone Generator App (off which there are many) we can place the Smart Phone inside the cabin whilst using our NVH software & Mic outside the cabin to capture leakages via seals, seams and bungs etc.
Tone Generator App
Tone Generator App
With the Smart Phone inside the cabin emitting a fixed frequency between 200 Hz and 20 kHz we can use the NVH Mic to capture sound leakage from the cabin.

10 kHz was chosen from the Smart Phone as this falls centrally within the human sensory spectrum (for Noise and Vibration) of 0 - 20 kHz
NVH Mic
NVH Mic
Below we have the results of leakage present at the top left had corner of the RH cabin door drop glass seal
Cabin Leakage
Cabin Leakage
For your initial reference of cabin leakage, measure the sound level of the tone emitted from the Smart Phone with the cabin door open. (Here we have 74.3 dB)

This will act as your peak reference by which to judge any leakage found with the cabin door closed. As you can see the peak sound level captured at the leaking drop glass seal was 43.6 dB which is clearly protruding from the noise floor at approx. 16 dB

Remember as per the forum post mentioned above post50851.html#p50851 you could also use the Frequency Generator built into the NVH software to generate a fixed frequency sound of our choice.

With that said, a greater degree of flexibility is allowed using a
Smart Phone as we do not introduce a cabin leak due to the Frequency Generator wiring (3.5 mm jack to 3.5 mm jack cable) passing into the cabin (to the In Car Audio Aux socket) from the Laptop outside the cabin.

With that said we could use the Laptop Bluetooth feature to pair to the In Car Audi system.

Food for thought once again and I hope this helps, take care……Steve

Diaz310102
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Joined: Fri Jan 26, 2018 7:04 pm

Re: Wind Noise Detection/Follow on

Post by Diaz310102 »

Hi Steve, I was visiting a dealer to sign a car off after a wind noise repair and was thinking of another way other than using your parking sensor probe setup. The NVH mic came to mind, so the night before the visit, I put it to test on my own car. The result’s were great. Used it on the car at the dealer with confidence. No need to use a smoke machine. I tied it in both NVH and PS7. Both worked great although I like the NVH app because I can say where I am etc.

I thought I came up with something no else thought of, but I was very wrong. :D

Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 1578
Joined: Sun Aug 25, 2013 7:22 am

Re: Wind Noise Detection/Follow on

Post by Steve Smith »

WOW, thank you for taking the time to feedback and share your experience as it is great to hear how these theories actually work and are used in practice.

This test has saved hours of work when looking at wind noise from frameless windows where the rake of the drop glass has compressed the window seal over time

Adjusting the rake or changing the seal works a treat and being able to measure before and after confirms the repair process

You may find this one useful in the field too viewtopic.php?p=98624#p98624

Thank you agin for the feedback, take care......Steve

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