Engine Compartment Insulation - Recommendation?
- Thread starter jviss
- Start date
Jim
I started looking at sound reduction but chose to explore the way trucks have been addressed not boats. They have been doing it longer and more trucks than boats. Here is a link that I found helpful. Not fully scientific but lots of common sense.
http://www.cumminsforum.com/forum/9...s-consider-when-soundproofing-your-truck.html
I decided I will tackle this task but not immediately. It will be when I pull the electrical lines off for the new electrical system. At that time I'll have clean walls to tackle the sound proofing then reinstall the electrical.
It is never just one thing with a boat.
John
I started looking at sound reduction but chose to explore the way trucks have been addressed not boats. They have been doing it longer and more trucks than boats. Here is a link that I found helpful. Not fully scientific but lots of common sense.
http://www.cumminsforum.com/forum/9...s-consider-when-soundproofing-your-truck.html
I decided I will tackle this task but not immediately. It will be when I pull the electrical lines off for the new electrical system. At that time I'll have clean walls to tackle the sound proofing then reinstall the electrical.
It is never just one thing with a boat.
John
I am almost done with my reinsulating project, I removed the old lead foam deteriorating falling down unsightly crap, scraped and scraped to get the original foam backing with the adhesive off using Goof Off to help release the tenacious stuff. I have been applying the material from Sailors Solutions which is a 12" x 12" tile sandwich of adhesive then a foam (not lead) about 1 1/4" topped by a fairly thick super tough reflective membrane. They claim the foam is what truck manufacturers use to silence diesels. I will know shortly as I have about a final day of installing the remaining tiles and taping the seams with a foil tape as I don't like exposed corners or seams. When I make noise in the engine compartment it already has a very dull absorbed sound. The only complaint I have with the material is that there is a plastic film on the reflective membrane that needs to be removed and the only reference to removing it was a how-to video far down on the web site, now I have to remove the taping and plastic in the generator enclosure as I did not know to do this before finishing up that area, mutter mutter! Even if it is not as quiet as I hope it to be it already is a vast improvement in appearance and no more leaded foam falling all over the place. Anyone else ever stepped on a bit of that leaded stuff on teak and holly sole, it's almost permanently stained.
Excellent explanation and clarity, at least for me. Thanks @jviss
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Me too!!
I went to Defender and looked up the 1" sound barrier stuff that seemed to be what @Rich Stidger et al. were discussing. This is the linked material, I think.
https://www.defender.com/product.jsp?path=-1&id=3018150
So I took the...
Sound Reduction Challenge...
Here is the sound reduction Data by ASTM standards, which is the common reference to all Sound Reduction Material. Note: Personal Protection by maximum 80 dB volume in not the key here, but sound frequency reduction.
Here is the Defender Material Data..
https://www.defender.com/pdf/301872_DATA.pdf
At the bottom, is a table with Sound Absorption Coefficients at octave band center frequencies, Hz.
Their label is "Sound Absorption per ASTM..."
A Sound Absorption Coefficient of 1.0 = 100% of that Frequency absorbed and one of 0.14 = 14% absorbed.
The largest was 0.79 at 2k Hz.
Next is the Owens Corning Sound reduction Duct Board's data at 1" comparison thickness.
https://dcpd6wotaa0mb.cloudfront.ne...etR-Duct-Board-Data-Sheet.pdf?v=1476984225000
This significantly out preforms the Defender Material as a sound reducer.
Example 0.99=99% at 2kHz
The only frequencies of lower reduction were the 125 and 250 Hz, which are the low frequency "Humming"
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Ok like @jssailem investigated, what was a Auto Diesel noise? That link discussed the MLV lead layer material.
So I looked up a full testing of sound by a Diesel Engine...
Gulp! What a study...
http://acta.fih.upt.ro/pdf/2014-3/ACTA-2014-3-21.pdf
You are welcome to gag on that, but here is MY take away...
The highest volume [dB] takes place a the ≈2k Hz frequency [based on Crank shaft position]
But the "Hummmm" is the 125, 250 Hz. which amounts to most of what I hear, but it is does not drown out human speaking frequency.
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So if you want Volume control use the Duct board.
If you want very little "Hummm" reduction, with Sound Reducers they work about the same, only about 37% maximum for Defender Material vs Duct Board at 19%,
Don't gag to much on this.
As I said, I was curious.
Jim...
The foam in my engine compartment was a disaster. It had some sort of plastic film with fibers (like strapping tape has in it) and was frayed and disintegrating.
I used Reflexite right over the top of the old foam, stapled to the substrate.
It is not the best, but it keeps the dust down, the noise down some, and the heat in the engine compartment some.
It also significantly brightened the engine compartment ( maybe the most important thing) and is easy to clean.
A short video....
Greg
I used Reflexite right over the top of the old foam, stapled to the substrate.
It is not the best, but it keeps the dust down, the noise down some, and the heat in the engine compartment some.
It also significantly brightened the engine compartment ( maybe the most important thing) and is easy to clean.
A short video....
Greg
Wow great audio. I can hear the Crank shaft position noise
And I do hear the "Hummm"
Jim...
PS: I heard your voice, Greg, above all the open or closed noise.
I am not a diesel guy...is it supposeD to sound like that, or do you hear something that doesn’t sound right? She seems to run well, but I don’t really use it all that much.Wow great audio. I can hear the Crank shaft position noise
And I do hear the "Hummm"
Jim...
PS: I heard your voice, Greg, above all the open or closed noise.
Greg
No! It sounds just like mine.
Good shape to me, by just sound.____
I was joking about the in depth study on my post #25 above. That study found all major diesel engine noises were associated with Crank Shaft position.
Of course it does. When the fuel fires versus exhaust Cranks Shaft position, etc. Over all they found the highest volume noise was at the ± 2k Hz frequency, but they mapped out, all sorts of NORMAL noise conditions versus Crank Shaft position.Sorry, I didn't intend to make it mean... Alert for you!!!
Jim...
That is my attachment method in my genset compartment.
I dumped the tack/washer type nails.
The limestone tile is "way cool" add on. I wonder if it gets the "Hummm" reduction award.
Jim...
Looks good, Chip. So, I'm new to this; what's the 'design' of your treatment, meaning, what are the mass, dampening and absorbing layers? I got that the VCT is the mass layer. Is the board both dampening and absorbing? Is it flexible?
Thanks.
Thanks.
This board is normally used for HVAC duct work. it is stiff, but easily cut. it does not really bend. Below are the acoustic properties for the 2 most common Johnson Manville Duct boards.
Thank you! Yea, I am going to need at least some stuff that bends, follows contours; the inside of the fiberglass companionway stairs isn't insulated at this time, and I bet if I do that it will quiet things down a lot! Not that it's super loud now, but I think it can be a lot better.
The Duct Board doesn't bend so much, but I have shaped it by thin inside cuts and it does "bend" sorta.
Not much that I can't make fit.
Jim...
Ok! No end to what I learn on this site ;-). Just wanted to make sure I wasn’t missing something. Like I said, she runs well and starts very dependably. But I don’t know a lot about them. Changed my fuel filters for the first time in 4 years a few weeks ago...had me very nervous. But all went well.No! It sounds just like mine.
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I was joking about the in depth study on my post #25 above. That study found all major diesel engine noises were associated with Crank Shaft position.
Sorry, I didn't intend to make it mean... Alert for you!!!
Jim...
Greg
Most yanmars before 2005 did not have intake silencers on the engine. You would be very surprised by how much bass noise is created from the intake pulses. On our 2004 4JH3E ( 56hp) the cabin noise was terrible even with the insulated engine compartment. It was impossible to have a conversation while motoring. My solution was to attach a 4 foot long flexible carpet cleaning hose of the same diameter ( I believe 1.5 inch) on the intake pipe and coiled it behind the engine. The intake pusles were significantly reduced to the point you could talk in the cabin while motoring. $10 solution.
I was surprised too, until I read and partially absorbed, the Italian Engineering report of Diesel Engine Noise, in the link of my post #25.
The low frequency "hummm" is basically mechanical noise. Most sound reduction material is Terrible to stop that.
However the air "intake stroke" it OPEN from your engine compartment intake to the cylinder. [The open cylinder exhaust is water quenched and muffled.]
Most of the sound reduction material is designed to reduce noise frequency in the normal human hearing/talking frequency range.
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Sound likes to move in a "straight" line. By coiling the hose, you are reducing echos, reverberations and harmonics.
The spiraling is actually changing dampening frequencies.
Clever idea!
Trivia: One of the earliest engine mufflers was a coiled hose pipe.
Jim...
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