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Old 01-02-2023, 06:24 PM
edmondthx1138's Avatar
edmondthx1138 edmondthx1138 is offline
Join Date: Jun 2021
Location: Tucson
Posts: 20
Default Soundproofing Engine Cowling and Firewall

I am interested in reducing sound and vibration levels as perceived in the cockpit. ANR headsets are fine, but hearing loss occurs over a long period of time being exposed to noise.

I would like to add soundproofing material to the cowling of my RV-12iS.

I also would like to add soundproofing material to the firewall and avionics bay. I suspect this would be best accomplished inside the cockpit as much as possible to facilitate condition inspections, etc.

For overall soundproofing, the cowling seems a logical and relatively easy solution, as there is room for the material.

Other than added weight and recalculating the W&B, does anyone have any thoughts on this topic?
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Old 01-02-2023, 06:48 PM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 8,699

Originally Posted by edmondthx1138 View Post
I also would like to add soundproofing material to the firewall and avionics bay. I suspect this would be best accomplished inside the cockpit as much as possible to facilitate condition inspections, etc.
Please read the many posts of actual tests done by DanH, on the fire danger of cockpit side firewall insulation.

The easiest and best solution to your problem is to wear earplugs under your ANR headsets.
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Old 01-02-2023, 07:01 PM
Mikeyb Mikeyb is offline
Join Date: Nov 2018
Location: Pasadena ca
Posts: 242

Just one of many posts on the subject. The consensus is:
1. It doesn’t work
2. Adding anything to the inside of the firewall is a fire/smoke hazard.
SN 83764
Hartzell Composite CS
Phase 1 complete 10/29/22
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Old 01-02-2023, 07:22 PM
Piper J3's Avatar
Piper J3 Piper J3 is offline
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,856

I agree with BobTurner above..... I have LightSpeed Zulu3 ANR and wear Bluetooth hearing aids. I have a special program for the hearing aids that I turn on via cell phone app. The hearings aids go into 'Mute" so they act like an earplug but they also function with Telecoil loop that allows EMF induction from the voice coils in the headset to present as real-time high-fidelity audio without background noise or feedback. The end result is concert hall fidelity with a soft turbine-like engine noise. Pretty much like sitting in first class on a 747. Very pleasing and works charm....
Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 830

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father - CFI) - USAAF 1st Lt. Captain B-17H
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Old 01-03-2023, 04:02 PM
Handclutch Handclutch is offline
Join Date: Feb 2015
Location: Bendigo, Australia
Posts: 152

+1 for what Jim said. The other day I forgot to turn on telecoil and the difference was remarkable. ANR still working but engine noise much louder.

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Old 01-04-2023, 06:25 AM
Avanza Avanza is offline
Join Date: Jul 2020
Location: Vastervik Sweden
Posts: 226
Smile How worried should I be ?

I suggest, check cabin with a Noise level meter.
The headset will provide a certain nr of dB.
If the noise level in the cabin is 105 dB and the headset gives a reduction
of 20 dB, you will be at 85 dB which is considered safe for 8 hours.

Good luck
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Old 01-04-2023, 06:36 AM
Mike Meehan's Avatar
Mike Meehan Mike Meehan is offline
Join Date: Apr 2021
Location: Decatur, TX
Posts: 97
Default 82 dB

The ambient sound level in our -10 is about 82 dB at cruise. Moderately loud, but not significant. Check out this thread.
Mike & Becky
RV-10 - N260MG
Decatur, TX (KLUD)
2023 Donation Paid
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Old 01-04-2023, 07:05 AM
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MacCool MacCool is offline
Join Date: Aug 2020
Location: central Minnesota
Posts: 1,482

My Apple Watch has a pretty sophisticated hearing protection and sound-measuring function and I’ve occasionally had it warn me about cumulative low-frequency noise exposure when on my tractor…some implements more than others. OTOH, I’ve never had any notifications about noise exposure in the cockpit of my airplane, even on a long flight. You can set the exposure levels according to your preference. The watch will warn you if you exceed a set threshold for more than three minutes. Mine is set for 80db I think.

As Bob said…a pair of earplugs with a sound brake, such as Surefire Sonic Defender, worn under noise cancelling headphone will work well in reducing noise exposure if one is concerned about that. I do that routinely under my electronic ear protection in competitive shooting events, depending on firearm, caliber, and indoors vs outdoors. I’ve never found it necessary when flying. If the user finds that it impairs ATC communication then they could always open the brakes, which will still contribute to good noise reduction but improve hearing of voice frequencies.
RV-9A, 2011, bought flying
IO-320D1A (factory new), C/S
Dual Pmags
IFR equipped
AFS 5400/3500, G5, IFD440 navigator,
bunch of other stuff

Last edited by MacCool : 01-04-2023 at 07:19 AM.
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Old 01-04-2023, 01:20 PM
RV8JD's Avatar
RV8JD RV8JD is offline
Join Date: Jan 2005
Posts: 745

I use the 3M E-A-R Classic Plus ear plugs under my ENC headset (currently a DC ONE-X). I buy them by the box. They are slightly longer than their regular Classic ear plugs which makes them easier to insert. They have an NRR of 29 dB to 33 dB. I've been using headsets in conjunction with ear plugs since the mid-80's. Especially helpful in very noisy towplanes.
Carl N.

Last edited by RV8JD : 01-04-2023 at 01:43 PM.
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