Quiet Cabin

[BruceMe]

My non-insulated RV-4 is much noisier than I'd prefer. What is the least weight simplest and effective way to improve it? Bubble wrap, foam insulation, carpet? Wondering what others have done, other posts, articles or ways to make it flyable. Objective results would be best (db lost per lb added)

-Bruce

[Auburntsts]

A good ANR headset.

[RVbySDI]

There is a great deal of discussion on this topic from many years of past posts. Search is your friend on such a topic (3rd from the right on the blue ribbon just above this thread). Here is a search I did on "cabin insulation":
http://www.vansairforce.com/communit...rchid=32789943

[bkervaski]

Just adding Carpet made a significant difference to one of our local 7 guys .. he put a layer of foam and then carpet on the floor and in the luggage department .. didn't bother with the side panels it made such a difference.

[dmat]

ANR headset +1

[snopercod]

Originally Posted by Auburntsts

A good ANR headset.

That was my original plan as well, but what I failed to consider was that every time I keyed my mic, all that cockpit noise was being broadcast to ATC. The noise was so loud that they could barely understand me. Here's how I solved that problem:

1. I added sound insulation to the cabin and improved the canopy seals.
2. I added a full 1" of foam insulation to the cabin side of the firewall.
3. I added foam/rubber insulation to the floor.
4. I bought a Sigtronics S-20 headset with a noise-cancelling mic
5. I added a Mic Muff over the microphone
6. I added down turns on my exhaust pipes
7. I adjusted my Icom A-210 as follows:

INCOM LVL = 051
MIC 1 GAIN = 10
MIC SQL = 026

[rv7charlie]

By far, the most effective thing I did on the 1st -4 I owned was to seal up air leaks.

Sealing leaks can be a lot of work, but should add minimal weight and minimal expense.

After that, just a good set of headphones; either noise cancelling or 'plug' type like QT Halos. If ear plugs don't bother you, the passive in-ear models can have noise reduction as good as, or better than the active over-ear models. And no batteries, and no head vise, and no weight on your head.

[gfb]

Originally Posted by snopercod

2. I added a full 1" of foam insulation to the cabin side of the firewall.

Careful here, with a fw fwd fire the foam could offgas/melt into stuff you don't want in your lungs. There is a thread on this on the forum, some of the foam insulation breaks down into seriously nasty stuff when heated.

[snopercod]

Originally Posted by gfb

...the foam could offgas/melt into stuff you don't want in your lungs.

I used Super Soundproofing Foam from ACS which supposedly "has fire retardant qualities and meets FAR 25.853a Appendix F, Pt1". I have no illusions that the stuff won't burn and give off toxic fumes, but I decided that I would rather take my chances. I did install a temperature sensor in my lower cowling so I would (might) know if there was a fire up front. I also installed a spray header in the engine compartment leading back to a receptacle on my panel that my Halon fire extinguisher will fit into.

[sglynn]

Bruce
There are sometimes presentations at fly-ins from sound engineers like Oshkosh and others. Their content reduced to the executive summary is:

1. Seal gaps. Gaps is the number 1 source of sound getting into the cabin.
2. Stop vibrations. This is number 2. Use foam with an aluminum foil on one side to add a little weight which changes the natural frequency of aluminum skin so it doesn't vibrate in the wind as much. This is damping. (Note there is no such word as dampening). Sound engrs say, "Dampen vibrations).
3. Absorb noise. This is the least effective, but the most attempted. Just use thick foam or other sound absorbing material. Carpet is an absorb-er.