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Old 05-25-2019, 08:38 PM   #1
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Homasote Soundboard Insulation

Has anyone ever heard of or used this stuff? It is a 1/2' thick 4'x8' sheet similar to plywood but it is listed as a sound deadening insulation.

I think it has an R-value of 1.2, but I am more interested in its sound deadening qualities.

I am hoping to cut down on the road noise and keep the roar of the screaming jimmy at bay. I love the sound of that engine and I can, and have, listened to its mechanical symphony clear across the continent, but I think it will be a more pleasurable experience for the family if its toned down a little.

I was planning on doing 1/2" rigid foam over the existing plywood, then 1/2" plywood over that. This would replace the foam but its double the cost per sheet, at about 1/2 the thermal insulation.

I think I will be ok with the loss of r-value, the floors on this bus are already 1.5" thick plywood so the heat gain/loss is slower than just sheet metal, but is the soundproofing worth double the cost? Are there better/cheaper options?

https://www.homedepot.com/p/1-2-in-x...6136/202090212
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Old 05-25-2019, 10:18 PM   #2
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What a coinkydink, while reading your post my email tones in, it's an offer from Amazon for this 3/4" Dynamat sound deadener.

https://www.amazon.com/gp/product/B0...3960_411509020
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Old 05-26-2019, 12:10 AM   #3
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Dynamat is a great sound dampener. I used a 1-1/4" thick version of it on my doghouse over the engine. I had purchased the homasote to try before finding Dynamat. The homasote is basically a compressed fiberboard which looks like it might replicate a sponge when exposed to water.
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Old 05-26-2019, 08:45 AM   #4
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Quote:
Originally Posted by peakbus View Post
The homasote is basically a compressed fiberboard which looks like it might replicate a sponge when exposed to water.
I had the same thought, reminds me of some LDF or something like that. I like the Dynamat, and I will probably use some of that under the drivers area and on the front skins, but its too expensive to do the entire bus floor or undercarrige.

I think I might try to get a small piece of the homasote for some backyard testing.
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Old 05-27-2019, 10:36 AM   #5
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And then there is availability to consider. None of the Home Depot stores around here carry Sound Board Sound Barrier and they won't ship it.

So I guess I will calculate the square footage of the engine compartment in my rear engine Blue Bird, because it is pretty noisy in there. But I want to build cupboards and a bed there. That in itself will provide some soundproofing, but more might be nice.

I wonder if dynamat has to be the top layer to be effective. Does anyone know about that?
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Old 05-27-2019, 11:48 AM   #6
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As far as sound deadening is concerned the black tar like portion of dynamat is doing the work. The shiny side serves to reflect heat. The bitumen (tar) portion can be installed top, bottom or middle but it needs to cover all surfaces without gaps for the best results. The reflective side needs to be facing open air for it to be effective.

The science of sound is quite interesting. Pour yourself a beer and read through this: /www.explainthatstuff.com/soundproofing.html as a start.

Hope this helps. Jack (AKA Dr. Science)
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Old 05-27-2019, 07:02 PM   #7
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Yeah, it did help, thanks. I can see I've had a tendency to equate insulation to sound deadening. But after reading that article, and scanning through some of the others on that site, I can see they're quite different.

Now I see that I need to rethink my plans for what to do on the engine compartment. What I have been thinking of will have minimal thermal bridging, but will still transmit sound effectively enough to have minimal effect on the noise level. But I am not there yet; I have time to think about it. Thanks for inspiring thought.
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Old 05-27-2019, 07:18 PM   #8
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A couple of interesting links I just ran across:

https://www.soundproofingtips.com/soundproofing-floors/

That first one has links to products listed on Amazon that fit into the categories they discuss, such as:

https://www.amazon.com/Roberts-70-19.../dp/B008N6Q7HI
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Old 05-27-2019, 07:25 PM   #9
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Or this stuff: https://www.amazon.com/Loaded-Soundp.../dp/B008JHE1P6

Now I understand why the vinyl flooring I pulled out of my bus was so heavy.
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Old 05-27-2019, 07:57 PM   #10
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on my DEV bus I dynamatted the metal then insulated with a product called themoguard FR. all in the drivers area and it made a HUGE difference in engine noise.. and along with fixing how the body and floor were mated pretty much eliminated engine heat.. my A/C actually stands a chance up front now rather than just barely cooling..



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