Sound deading material.

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NJ-boatbuilder57
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Re: Sound deading material.

Postby NJ-boatbuilder57 » Tue Sep 11, 2018 1:32 pm

Well, yes & no. Hearing is logarithmic. While 3db is a doubling (or halving) in mathematically-calculated change of level, the perception of doubling (or halving) of acoustical loudness is 10db.

(former sound engineer here....)

Chris_P
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Re: Sound deading material.

Postby Chris_P » Tue Sep 11, 2018 3:37 pm

Different materials attenuate different Db levels.

The best material for an outboard would be a dense material. Perhaps 1# Vinyl Septum epoxied inside the cowl. I have some I could try.

One of the offerings of my company is sound attenuation. Never tried it on my hobby though. We mainly do Natural Gas Plants near residential neighbourhoods.

Chris_P
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Re: Sound deading material.

Postby Chris_P » Tue Sep 11, 2018 3:38 pm

Something like this may work well? I have not tried it myself.

https://www.ebay.com/itm/SOUNDCOAT-1-2- ... 1438.l2649

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chris
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Re: Sound deading material.

Postby chris » Tue Sep 11, 2018 4:09 pm

I used some 1/2" thick carpet pad from hardware store. The multicolored kind, made of little chunks of different foam rubber.
It worked very well, a very noticeable difference in sound level. Can just about have a conversation between front and back seat.
My only issue is that the spray adhesive I used is not the best. I used 3M super 77 If I recall. Seems to stay sort of soft, and the foam will peel away in spots with that stuff. A good old rubber cement brushed on from a can would be best.
1955 10hp, 25hp, 1957 18hp Johnsons. 1958 35hp, 1972 50hp Evinrudes. Among others...

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chris
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Re: Sound deading material.

Postby chris » Tue Sep 11, 2018 4:14 pm

Chris_P wrote:Something like this may work well? I have not tried it myself.

https://www.ebay.com/itm/SOUNDCOAT-1-2- ... 1438.l2649


I really like the looks of this. I wonder if the adhesive is good?

Some other types of stuff have been mentioned here, but it is my opinion that you would want a porous and not too dense material for the type of sound reduction we're after here. If putting something with a smooth backing or whatever, I'd think the sound waves would just continue to bounce around. Sound studios have porous foam shaped like peaks and valleys.

The best solution I'd think would be some Dynamat type product with soft foam over top of that.
1955 10hp, 25hp, 1957 18hp Johnsons. 1958 35hp, 1972 50hp Evinrudes. Among others...

crosbyman
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Location: Montreal Canada

Re: Sound deading material.

Postby crosbyman » Tue Sep 11, 2018 5:39 pm

NJ-boatbuilder57 wrote:Well, yes & no. Hearing is logarithmic. While 3db is a doubling (or halving) in mathematically-calculated change of level, the perception of doubling (or halving) of acoustical loudness is 10db.

(former sound engineer here....)



well of course I was talking logarithmic stuff :roll: since our hears all vary in perception with age and ...wax content :lol:

http://www.animations.physics.unsw.edu.au/jw/dB.htm#log

(former Telco transmission man here ...)

PugetSoundBoater
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Re: Sound deading material.

Postby PugetSoundBoater » Tue Sep 11, 2018 6:43 pm

I used the Soundcoat brand as in the ebay listing Chris posted. It cut nicely and the peel back adhesive was very sticky. I took my time and made carefully measured paper patterns, resulting in a nice neat job. Used this on a 15 hp cowling but have yet to try it out on the water for results.
"We only learn in two ways,one from reading,the other by association with smarter people" Will Rogers

PugetSoundBoater
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Re: Sound deading material.

Postby PugetSoundBoater » Wed Sep 12, 2018 12:29 am

Here are 2 photos , before and almost completed on the 15 hp cowling. I made patterns off my other 9.9 since the insulation on the one shown was too far gone to make a good pattern from.
IMG-20180527-01143.jpg
IMG-20180527-01143.jpg (315.38 KiB) Viewed 38 times
IMG-20180418-01087.jpg
IMG-20180418-01087.jpg (410.54 KiB) Viewed 38 times
"We only learn in two ways,one from reading,the other by association with smarter people" Will Rogers

reivertom
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Location: Eastern Kentucky

Re: Sound deading material.

Postby reivertom » Wed Sep 12, 2018 1:33 am

I wonder if that spray on or brush on rubber sealer they sell on TV would work? You could build it up a few layers and it would be like a thick rubber sheet.

SteveH
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Re: Sound deading material.

Postby SteveH » Wed Sep 12, 2018 5:46 am

Somewhere I read about a guy who put a plastic bag over the power head, put the cowling back on and used spray-in foam...


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