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Old 05-15-2022, 09:11 AM
Camillo Camillo is offline
Join Date: Sep 2006
Location: Roma, Italy
Posts: 531
Default High cabin noise (even with ANR headset)


I haven't flown too much since completing my -4. So, I am still fixing some issue.

Now, I feel that even with an active noise reduction headset (Zulu) the noise in the cabin is really high when RPMs are over 2.000. Even worst when side vents a-la-RV10 are opened. I have a 4 exhaust system.

Noise is way more than that on my previous -9A. The latter had the complete Classic Aero Design padding and pockets (side pockets, rubber floor). The -4 has nothing. Could the upholstery make the difference?

How can I improve the soundproofing? I read that a padding on the FF, cabin side, will not improve the SP...

RV4 IO-320, Catto 3-blade, Christen, I-BILT
Flight time: 20 hour
Status: flight

ROME, Italy
RV9A O-320 D1A, Hartzell C/S prop, slider, I-PRCA
Flight time: 350 hours
Status: SOLD
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Old 05-15-2022, 11:09 AM
wcalvert's Avatar
wcalvert wcalvert is offline
Join Date: Jan 2019
Location: Anacortes Wa
Posts: 454

Camillo, this is all from my experience (lots of I's in this write-up!)

On my -7, the noise level was very high (to my ears at least, my first extended exposure to the propeller aircraft). The sound seemed to be coming from the floors, ie. I could move my feet around to different spots and change the sound level by damping an area with pressure from my foot. There was still engine/prop noise, but the sound from the floor was much less.

The solution was to build a sandwich of insulating materials that covered the floor area from my heals up to the firewall. I used 1/8" heavy rubber type material on the base, on top of that 1/2" of heavy wool felt (horse blanket!) topped with a thin layer of non skid material. All was bonded together with contact cement and is not attached to the floor itself. The sound level difference is amazing, and it added about 8 lb to the aircraft, a worthwhile tradeoff for me.

There is also a similar but lower level of sound from the sidewalls, and a pad there might be helpful but in my mind not worth the weight.

This approach basically changed the weight (and maybe the stiffness) of the vibrating floor panel, changing the frequency where it was most likely to resonate. Damping and also absorbing sound.

So maybe the first effort would be to identify if you have a similar problem, experimenting while in flight. Just for reference, I fly the Catto three blade as well but behind an IO-360, 4 into 2 Vetterman crossover exhaust.

Good luck and keep moving forward. Cheers!
RV-7 Tipper
Bill (Wild) VA-165 '90-'93
Anacortes, Wa

First Flight 7/17/2021!! 200 hours 6/22
- Been there, Donated 2022
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Old 05-15-2022, 11:31 AM
FireMedic_2009 FireMedic_2009 is offline
Join Date: Nov 2016
Location: Tampa, FL
Posts: 263
Default Sound proofing considerations

Something to think about. If do you use any material that can catch fire or smoke and the engine compartment catches fire the smoke would incapacitation you before you hit the ground. Of course to insulate the firewall from heat on cockpit side you want to use fiberfaux and stainless steel foil on the engine compartment side. Dan Horton has a good description on how to do it. You also may want to do that on the belly of the plane from the exhaust exit back 3-4 ft. There was an RV10 that caught fire and lucky the pilot was flying barefoot and felt the heat from the floor and realized the engine was on fire and landed the plane. Part of the floor board was burned away by the time he landed.

After insulating the firewall on the engine you can most likely use wool on the cockpit side of the firewall for some soundproofing
RV-6A IO-320 FP sold
RV3B O-320 160hp
Donated 2018 and continue annually
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Old 05-15-2022, 12:22 PM
wcalvert's Avatar
wcalvert wcalvert is offline
Join Date: Jan 2019
Location: Anacortes Wa
Posts: 454

Hear what you're sayin'. The fire risk was part of my decision... also keeping the pads removable does give the option of pulling them off the floor if necessary! Just balancing absolute risk against likely risk during the life of the plane.

... and now about flying barefoot !!!
RV-7 Tipper
Bill (Wild) VA-165 '90-'93
Anacortes, Wa

First Flight 7/17/2021!! 200 hours 6/22
- Been there, Donated 2022
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Old 05-15-2022, 01:07 PM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 8,247

By far, the most cost-effective approach is to wear foam ear plugs as well as your headphones. Turn up the radio/intercom volume as needed.
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Old 05-15-2022, 01:21 PM
theduff theduff is offline
Join Date: Jan 2012
Location: L-18
Posts: 375
Default RV-4 Cabin Noise

I have a high powered RV-4 (over 210 hp) with a 4 into 1 exhaust and absolutely no interior or sound proofing other than leather seats. When I upgraded my 320 w/ 4 into 2 exhaust to the high powered IO-360 with the header the noise went up substantially. The floorboard idea deserves consideration but in my case with a 1000 lb airframe I didn’t want to add the weight yet.
I’ve tried several brands of ANR headsets including the Bose and the new David Clark’s and AKG’s and to my amazement these headsets seemed to amplify the high frequency noise ! I’m talking painful as in making my ears bleed... tongue in cheek but was uncomfortable enough to terminate the flight. It seemed as if the ANR system was being overwhelmed by the high noise environment. Since I switched power plants I’ve been using my old Sennheiser ANR’s which out perform the newer ANR’s by a large margin. When I spoke to DC about this they explained because of the large amount of high frequency noise I needed headsets with better passive noise protection than the DC’s offered (same explanation from Bose). DC gladly accepted my return and even apologized that their headsets didn't work out for me. Excellent Customer service. The ANR does well with the low frequency range but my noise appears to be in the high frequency range. ( somewhat subjective) and I need a balance of both passive and active to be comfortable.
My Sennheiser’s seem to be the best balance that I’ve been able to come up with so far and recently was able to purchase a new old stock set to keep me flying. I’ve not tried the Zulu’s.
I’d appreciate others thoughts but it seems to me the modern light weight ANR’s are not the answer in our high noise environment.
RV-4S (slider) Builder and 1300 hr RV Pilot

Last edited by theduff : 05-16-2022 at 09:48 AM. Reason: clarify
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Old 05-15-2022, 04:24 PM
gasman gasman is offline
Join Date: Mar 2007
Location: Sonoma County
Posts: 4,393

I purchased 2 sets of Lightspeed QFR XC headsets around 2007. They worked great. and they were cheap!

Years later, I purchased the first Zulu offered..... One flight and back to the QFR's. Zulu went back into the box and shelved.

Don't count on electronics to solve all of your cockpit noise problems. Rely on passive noise protection first, then ANR. In the past, headset manufacturers would list passive and ANR in their specifications. They don't seam to do that any more. Look for, and ask about 23db passive minimum on any headset used in an RV.

VAF #897 Warren Moretti
2021 =VAF= Dues PAID

Last edited by gasman : 05-15-2022 at 05:02 PM.
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Old 05-15-2022, 08:00 PM
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DanH DanH is online now
Join Date: Oct 2005
Location: 08A
Posts: 10,761

First make sure there is no mechanical contact anywhere which could transfer engine vibration to the airframe. For example, if one of the baffle walls is too tall and contacts the cowl, it can resonate another part of the airframe. Same for exhaust pipes and other parts.

The canopy assembly can vibrate due to prop blast.

Lining a single wall floor skin with rubber foam is a bad idea, period. We've seen multiple reports of melted floors right here on VAF. Assuming the owner does not wish to shield the exterior of the belly, a separate floorboard with an air space between it and the belly skin would be safer and probably just as effective.

Can't endorse wool or anything else on the cabin side of the firewall, even with a good insulation package on the engine side. The issue is small point hot spots, for example, AN3 bolts through the insulation and firewall.

I'll have very complete insulation kits available shortly, cored with better than fiberfrax 970.

FWIW, after a few different Lightspeed models over the years, I've switched to passive in-ear headsets and am unlikely to ever go back.
Dan Horton
Barrett IO-390
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Old 05-16-2022, 07:08 AM
FinnFlyer FinnFlyer is offline
Join Date: Aug 2018
Location: Bell, FL
Posts: 664
Default Floorboars

I too have noticed a significant difference in noise when resting my heels on the floorboards and lifting them of off them.

Don't know if it's prop blast, exhaust pulses or just some resonance.

I have 1/8" fiberfrax sandwiched between 6" wide SS shim stock from firewall to under pilot seat.

N214FL RV-4 Mazda 13B Renesis First flight 20 Feb 2021
N46AZ RV-3B Mazda 13B EFI -- Bought -- Flying
N993FL RV-3A Mazda 13B NA 575 hours
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Old 05-17-2022, 05:43 AM
fixnflyguy fixnflyguy is offline
Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 1,554
Default What I did

I built my -4 with the Vetterman 4 pipe, which historically created drumming in the floor of the -4, depending on pipe tip angling. I had no floor covering for first several flights, and had slight noise , but the floor also got pretty warm..I was wearing boat shoes and could feel it. At my day job, I used a lot of high temp silicone foam rubber sheeting (1/8" thick or so) for various airliner flame resistant applications, pretty much the same stuff the red valve cover gaskets are made from. Its high density, burn proof and easy to cut. I made pieces that fit the footwells and the battery tunnel. In the foot wells, I also made .025 titanium (SS would work also ) overlays. These pieces are bonded to the floor with a small bead of red silicon RTV. No more heat, less sound. The titanium makes a nice finish for your heels to slide on. As a last note, I fly with Halo in ear headsets, which provide really good noise elimination and comfort second to none.
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Bill E.
8A7 / Advance NC
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