Metal interior sound deadening?

I am about to install my metal interior before I cover the fuselage. I am a little worried that there "might" be more noise than I would like, (even with Atlee's 3" gutted muffler and ANR headphones). Has anyone had any luck with some kind of sound deadening insulation?
My side panels and headliner are .016 alum. and metal floorboards (.032 and .040). Airplane is a 2+2.
Laz[/i]

I glued fabric or vinyl to the interior metal and put carpet on the floor. Seemed to help, but does add some weight.

There are many products that can be used for noise attenuation, and the objective for your application should be to find the lightest product that gives the greatest attenuation at the frequencies your aircraft vibrates at. It is very, very easy to add lots of weight while producing only tiny improvements in the noise level, so if you choose to pursue this it will be worth your time to do a thorough investigation.

In an earlier life I spent a fair amount of time dealing with resonance issues on small steel structures. For the problem I was dealing with, the best solution turned out to be a 3M viscoelastic polymer bonded to a thin substrate (in this case it was a stainless steel foil). The combination of the polymer and the steel was tremendously effective in damping out the resonant frequencies, and the material worked over a wide range of temperatures. While working on the solution, I found that 3M was selling a similar product to Boeing. Boeing was applying sheets of the material to the inside surface of the fuselage. This product was optimized to damp out the resonant frequencies experienced in a jet, so it might be suboptimal in a Cub, but there's no harm in checking with the Boeing surplus store to see if they have any on hand. The 3M website may also be able to refer you to converters who sell their viscoelastic material bonded to various substrates.

Beech has extensive noise reduction programs for its aircraft. They use passive and active noise damping techniques. Are there any Beech employees on the site who can share the techniques used on Bonanzas and Barons?

The low cost automotive approach is a fibrous mat coated in a tar-like substance. I know this stuff is available through body shops, but I have never seen any performance data, so I can't tell you how much noise attenuation to expect, or the frequencies at which it's effective. I do know that it's rather heavy. Are there any Big 3, BMW, or Mercedes employees on the site who know more about those products?

Eric

Sound deadening

Body shops use a product that has thin aluminium tape with a thin putty stuck on the one side that can be cut in strips and stuck to new panels.
Helped on new car panels but I wouldn't want it in my airplane to add extra weight.

DYNAMAT
http://www.dynamat.com/

this may help

I have thought about this too. I think I will just get a better pair of headsets. I'm already half deaf.

A lot of guys are using that bubble wrap style insulation and using super 77 to adhere it to the metal. i also have al. floorboards when i installed i put small dots of silicone along the tubing between the floor boards and tubing, it went from a ringing sound to a dull thump when you tap on it and it does not weigh very much. alot of people do not like al. vs wood because of the noise but if installed correctly they can be as quiet and definetly lighter.

delete

One of the dynamat products is made specifically for this purpose and is DOT approved.

TacMat is approved by DOT FMVSS 302 and passes Federal Aviation Regulations

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http://www.dynamat.com/products_automotive_tac_mat.html

Try Soundex aviation insulaton available from Soundex Products Company in Southaven, Mississippi.

www.soundexproducts.com

I've used it in a Cherokee, and it works quite well. It is a black, viscoelastic polymer with a thin metal lining on one side. Comes in several different thicknesses and can be cut with scissors.

JimC

One of my sons has a Cessna 150/150 Texas taildragger in Colorado. The rebuilder of his plane used Soundcoat soundfoam throughout his fuselage. He called me on his hand heald cell phone yesterday from 11500 ft over Teluride, CO and the call was so clear and quiet that I thought he was in his truck. The cabin of his little airplane is so quiet earphones are not necessary. I bought some sheets of the foam for his brothers wide body Smith Cub project and a sheet from them that is milar covered for the back of the Cub firewall. Their web site is: http://www.soundcoat.com/index.htm
I do not know anyone at this company and am not an owner. I just know the stuff works but is expensive. Jerry McCammon

Thanks everyone! Lots of good ideas.
Happy Thanksgiving!
laz

Most of the noise I get in my CC is the the aluminum headliner rattling around from the wind when the door is open. Expecially when you slip it in. In the winter when the door ic closed it is pretty quiet. I have used most of those sound deadener systems and they work great, but they are heavy. I bet if you do all the headliner and side panel pieces you could pick up an easy 10 to 20 lbs. I think I'll invest in a good ANR headset too.
PR

Sound Deadening

I have seen a lot of guys use small strips of material bonded to aluminum on metal interior panels in Alaska. Reeve Airmotive sells the stuff and it supposedly works great (costs plenty, too) Usually a 2" wide strip by 6-12" long is placed somewhere near the center of the panel. From a vibration dampening perspective this makes sense. You are changing the natural frequency of the panel by adding a little mass and stiffness. It also weighs very little when used sparingly. I haven't tried it yet as my project completion date is more than a year away.

I originally purchased a lot of 1/8" Super Soundproof from Spruce that I was going to glue to the back of each metal panel. I have lots of it if anyone is interested!

sound proofing

If you have access to a beading machine to stiffen the panels this will eliminate the drumhead effect of the panel. It will also add strength to the panel, to resist oilcanning when you throw that moosemest in there.

soundproofing

I just wipe the flat panels with a little MEK or acetone and then apply a pencil sized bead of Hi temp silicone in an "S" or "X" shape. Stops the vibration with a minimal weight gain. It also does wonders for larger portions of the engine baffling. Mine don't crack out anymore.

Mine has X's of what I would call undercoating on the back side of the interior and extended baggage. I don't have any knowledge of what is was like without it.

Does anyone have experience with the 3M Damping Foil 2552?

It's a layer of viscoelastic polymer attached to a dead soft aluminum foil. It damps low frequency vibrations, with greatest effect in the 100 - 2000 Hz range. The technical data sheet deals in "Composite Loss Factor" instead of dB, so I can't compare it to the attenuation achieved by a good headset. If anyone knows how to convert composite loss factor to dB, it looks like it peaks at 0.3.

It weighs 0.17 lbs/sq ft, is resistant to intermittent exposure to mild acids and alkalies, most oils, grease, gas, kerosene, JP-4, hydraulic fluids, etc. Its operating temps are 32*F - 140*F and is survivable from -25*F to 175*F. It comes in rolls 36 yds long and up to 23.5" wide.

A rough estimate of the installed weight in my a/c is 8 lbs (!). This is for the firewall and the aluminum headliner and sidewalls in the cockpit and baggage compartment. I wonder how that compares to some of the other materials previously mentioned

3M tells me their 4014 damping product is especially well suited for firewall applications. They say 2552 and 4014 are both available through Aircraft Spruce.

Get a good headset! Save the weight.

sadams said:

Get a good headset! Save the weight.

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As intriguing as the 3M products seem, I have to agree that the best solution is probably a top notch headset with noise canceling.

Eric

pa12_pilot said:

sadams said:

Get a good headset! Save the weight.

Click to expand...

As intriguing as the 3M products seem, I have to agree that the best solution is probably a top notch headset with noise canceling.

Eric

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There is a difference between active and passive and what actually damages your ears.

Tim

Mine was a lot quieter after the rebuild. We did a couple of things to quiet it. First, we sprayed the back of the interior panels with an automotive undercoating product. It comes in an 8 oz aerosol can. It goes on thin and takes very little. This is the same stuff that Piper used for a while. Secondly, instead of using the metal ceiling, we used a fabric ceiling -- same as the covering material. It is tough, quiet and light. It also provides a couple inches of extra headroom in back. Finally, the widebody STC allows more latitude for interior installation. The extended baggage area is fully supported with makes it a lot quieter. Mine weighs in at 1,150 with a full electrical system and a pretty deluxe panel.