Acoustic/Sound tile substitute?

[daveschile]

Hello all,
I've been considering some different materials for the ceiling of my engine room (the underside of the pilothouse floor) to act as a sound insulator. I've found that acoustic tiles seem a bit expensive for what they are. The other day I found a package of this closed-cell foam stuff that is intended to go on your shop floor as "comfort pad." It's basically 1/2" thick foam like in a camping pad. Anyway, I got enough to do the whole ceiling for $10. Anyone care to comment on this? Or at least tell me why it's a stupid idea? Also, I'm thinking of just using contact cement to install it (stick it to the ceiling). Any other suggestions?

Thanks,
Dave

[Dutch Peter]

Don't know the stuff, but what springs to mind is:

- Oxygen coefficient (burn behaviour).
- Absorbtion of fuel, is top layer closed?

For fixing it to the ceiling:

- contact cement, at first, not a problem. But also mechanically secure the insulation. If you don't, it can come done and start a fire.

Yes, the reall deal, the good stuff is expensive and sometimes only because it has "marine" on the package. But you're also pretty sure it is designed for the marine application, something you'll always be wondering about with the Home-products.

[gonzo]

What is the heat resistance of the foam? It could melt or ignite.

[FAST FRED]

To get any real effect the sound absorber should contain at least 1lb sq ft of sheet lead.

www.soundown.com is a source for MARINE foam that works inside the engine space.

Anything will help in the cabin , even stuff from Home Depot , stuck on the overhead will absorb some noise.

FAST FRED

[asathor]

I would not use anything but testet and known materials inside the engine compartment or passenger compartment. It would be a shame to have to abandon ship because of fumes.

I have some similar floor foam and it seems to be a bit to stiff and have too low mass to have any impact on low frequences (it will vibrate along with whatever you attach it too unless you constrain it).

I am thinking that you will need both some of the barrier materials to cut airborne noise transmission as well as constrained layer damping to cut structural transmission.

Constrained layer damping requires mass to work against so it is most effective if applied during the building process - but if you find that you have vibrating panels you can use it in combination with stiffening support that breaks the panels up into smaller sections (moving the vibration mode up to higher frequences where you can more easily damp it). You could also apply such a sandwitch of commercial or your own design to the pilothouse floor.

Since frequences below 1000Hz are increasingly difficult to dampen without a lot of bulk and mass you might want to borrow a spectrum analyzer in particular if you are not familiar with judging sound and noise. Or you can use a computer in combination with a good audio editing program like Adobe Auditions (make sure to get a good microphone as well I just bought a reasonably priced Audio Technica Electret condenser that can work with standard computer sound cards). I have attached an adobe spectrogram (music).

Fortunately you don't need laboratory grade equipment because you are merely trying to identify the frequencies of what annoys you so you can spend your money on damping that.

Compare your findings with the product litterature to see what materials may be suitable.

Motormounts cannot be overlooked as they cut structural borne vibration at the source. Airborne noise is by far the easiest to control.

by the way www.soundcoat.com is another excellent outfit.