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Old 11-04-2014, 18:51   #1
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sound insulation ideas?

For an engine room, or a generator. Resistance to moisture and fire are important.

Success stories to share?

What did you buy, and where?
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Old 11-04-2014, 19:30   #2
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Re: sound insulation ideas?

Lead. Joking, but only a little.

The key to sound reduction is vibration isolation (check engine mounts, etc) and heavy mass between you and the sound waves.

It's dead simple. You just have to find very heavy materials and isolate vibration.
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Old 11-04-2014, 19:43   #3
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Re: sound insulation ideas?

Managing vibration is a pretty technical field.

Let me distill the engineering into a few short sentences. Sound, noise, motion, etc is all just some form of vibration.

There are two primary sources of vibration, airborne and stuctureborne. Rarely will you ever be dealing with just one in the real world. Superposition and harmonics are the other issue. Basically you rarely get nice clean vibration.

On a more practical side you have a number of approaches you can apply. Absorption, deflection, elimination and attenuation. Note that its usually much easier (cheaper and quicker) to deal with the source.

The approach i usually take is
1) prioritise the sources for annoyance (some form of dynamic measurement may be needed but usually a process of elimination is good enough)
2) address the source (some form of before and after measurement either objective or subjective is needed to avoid chasing your tail)
3) address the effect (last resort)

Note that we only make one change at a time. (We are dealing with complex systems)
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Old 11-04-2014, 21:06   #4
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Re: sound insulation ideas?

Quote:
Originally Posted by dave777 View Post
For an engine room, or a generator. Resistance to moisture and fire are important.

Success stories to share?

What did you buy, and where?
A friend of mine used a lead foam product recently. I know a metal foam sounds kind of odd but there is one engineered for marine uses. It works but you need a bit of stand off space between the wall and the material; in this case it was a few pieces of double-sided tape. I suppose that's of what leftbrainstuff was referring to
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Old 12-04-2014, 23:21   #5
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Re: sound insulation ideas?

The product designed for sound reduction is called Soundown. Here is their website: Soundown (Sound Down, sound down, sounddown) - The Woldwide Leader in Noise Control Engineering

Here are the product details:http://www.soundown.com/Section%202%...nyl%20Foam.pdf

It uses mass loaded vinyl, not lead, between layers of foam with a foil surface. It should be available at any good marine store.
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Old 13-04-2014, 00:01   #6
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Re: sound insulation ideas?

I used this:

WEST MARINE Noise Control Barrier Material | West Marine

when replacing the insulation around our engine. It was easy to work with and had a descent sticking adhesive but use the hangers for the overhead pieces or it will fall down. I also sealed any of the exposed foam edges with aluminum tape as the old foam broke down very quickly when exposed to the heat and fuel/oil vapors.

It wasn't cheap but I'm happy with the result.
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Old 13-04-2014, 00:12   #7
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Re: sound insulation ideas?

The West Marine product is Soundown that is re-labeled for West Marine.
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Old 13-04-2014, 00:58   #8
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Re: sound insulation ideas?

I have tried a number of materials to sound insulate my engine bay - lead backed foam foil, rubberized carpet underlay, acoustic ceiling tiles, all with not too much success. The problem seem to be that good sound insulation requires 100% coverage. Just the smallest gap defeats the whole exercise and this is difficult to achieve in practice. My current method works very well in reducing the annoyance of engine noise. I find that in old age ive got to be pretty darned deaf. No doubt this wont suit everyone but hey, it works for me!
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Old 13-04-2014, 01:04   #9
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Re: sound insulation ideas?

Mascoat Sound Control is a marine sound insulation and viubration damping stuff I will most likely be using (as well as their DTM for thermal insulation). However, I don't believe it will dampen all sound, so using of proper foamy stuff will help.
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Old 15-04-2014, 18:50   #10
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Re: sound insulation ideas?

Thanks for the product references and advice.
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Old 16-04-2014, 10:30   #11
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Re: sound insulation ideas?

Hello, On my last boat I tried knocking the noise back on the cummins diesel with lead and the mylar covered foam, using the hangars as noted in a previous post. My biggest issue with it is it certainly burns, breaks down with the engine room fumes, and the mylar tape eventually falls away.
On my new boat with huge engine room has four to eight inches of Roxul marine board everywhere. This product is also called navy board in the U.S. I believe. It is basically spun basalt so is fire proof to 2000 +/- degrees F. doesn't absorb water, is non-toxic and relatively cheap. It comes in varying thickness and densities and is also mylar covered if you so desire. I love it!
cheerio, Greg
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Old 16-04-2014, 11:26   #12
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Re: sound insulation ideas?

As mentioned, sealing all gaps to stop air transmission of sound is the first step. There are special sound caulks but anything will do. Without this, the rest is wasted.

To stop sound transmission through a wall, mass is the key. Ideally multiple layers of mass that are "decoupled" so sound vibration in one layer of mass isn't transmitted to the next layer. Using the vinyl/foam sandwich does this by having the two mass layers (the heavy vinyl and the wall of the engine room) separated by the decoupling foam. Rubber is a good decoupler. So is air. The heavier the mass the better. Thus lead is better than vinyl. Thick concrete would be even better.

Besides the foam sandwich, Sounddown has a product made of two layers of plywood separated by a rubber layer. Not cheap but very effective.

Soundown - Barrier Acoustic Insulation, Carpet Underlay, Acoustic Absorption Materials, Damped Metal Panels, QuietClad, Quiet Clad
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Old 16-04-2014, 11:54   #13
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Re: sound insulation ideas?

"... covered foam, ...certainly burns, breaks down ..."
Foam can be dosed with fire retardants but since it usually is a petrochemical at heart, burning shouldn't be a surprise. And the toxins it can produce can kill you before the fire does. Foams also almost always break down as they age, how well they hold up has to do with how they are made and of course, there's no way to be certain of that unless you have an inspector at the factory who then rides along and escorts them all the way to delivery. Problematic at best, but still, a standard solution.

"On my new boat with huge engine room has four to eight inches of Roxul marine board everywhere."
Sounds like a wonderful alternative and an innovative product, but what small craft has even four inches of extra space all around the engine? Eight inches, good lord, that would mean 16" of extra clearance plus enough to leave airspace after that was installed. Either you've got a relatively huge boat, or it was designed from the ground up with that extra space. Retrofitting would be impossible for the average boater.

A much thinner layer (3/4" ?) might be a nice alterative for fireproofing, but you'd still need the density of lead sheeting to absorb vibration, and foam to de-couple it, to get the same acoustic benefits, wouldn't you?
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Old 16-04-2014, 20:39   #14
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Re: sound insulation ideas?

You are correct Hellosailor, The engine room was designed to be quiet and fireproof to start. I had a major lecture from a knowledgeable person before starting and had a chance to see and listen to his installation. when his engine was at full revs, the noisiest thing in the pilothouse was him closing the logbook.
The eight inches refers to the main watertight bulkhead with four inches on each side, four inches everywhere else. I lost a lot of room for sure, but used basically the whole aft ten feet of the boat for mechanical space. You can buy the Roxul marine board down to about one inch thickness I believe, so would give a good fire rating on top of everything else.
As a segue, I did the entire hull with four inches of the stuff instead of the usual foam.
Greg
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Old 13-05-2014, 15:55   #15
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Re: sound insulation ideas?

What if your galley sinks are above the engine? Seems like they'd act as speakers unless some sort of cabinet is built around them and it's covered in sounddown. Anyone done something that was effective with sinks?
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