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Beersmith 08-04-2011 09:26 AM

Engine Room Sound Insulation
I am looking at getting some Soundown foam to insulate my engine room. I am a bit confused by the difference between these two products:

Soundown Composite Insulation Vinyl Foam Sheets

Soundown Acoustic Absorption Foam

The second is much cheaper than the first, even at the same thickness. What are you getting with the vinyl foam sheets that the acoustic absorption foam doesn't have? The only thing I can figure out is the "barrier" feature, but that appears to be nothing but odor control, is that correct? Would I be extremely unhappy if I got the cheaper foam?

shogan50 08-04-2011 12:20 PM

The latter works by absorption, generally in the higher frequency ranges, the former more as a barrier in lower frequency. As a point of reference, I installed something similar to the foam, (1.5" noise attenuating ceiling tile), in my Islander 30 and could perceive no change in noise level. I fear in my case that the noise is getting transmitted right through the beds to the hull. If you install something, be please let us know how it worked out.

hellosailor 08-04-2011 03:56 PM

The barrier layer used to be LEAD in many products, but with the push to get lead out of the environment, and the cost of lead these days, vinyl is more common.

IIRC the science of it is that high frequency noise can be absorbed by foams, but low frequency noise consists of much higher energy levels (think of how you literally feel subsonic and bass noises) and you can only stop that energy by abosrbing it with something that has high mass (lead sheeting) and takes a lot of energy to move.

Depending on what your noise source is generating, one or the other may be more effective but the stuff with the "mass" layer generally should absorb more noise. It isn't just to block odor or moisture, it is there to absorb energy.

As shogan says, those lower frequencies may come through things like your engine bed. In theory you have rubber engine mounts, which stiffen as they age and should be replaced every 5 years or so. Those also dampen vibration and noise. In theory.

And plugging up every hole, every noise pathway, and using the right hangers/adhesives, is supposed to make a huge difference, regardless of the material.

Beersmith 08-04-2011 04:21 PM

Thanks very much for the info.

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