Sound deading material.

[nj-boatbuilder57]

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]

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]

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

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

[Chris]

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.

[Chris]

quote Chris_P:

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.

[crosbyman]

quote NJ-boatbuilder57:

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 🙄 since our hears all vary in perception with age and …wax content 😆

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

(former Telco transmission man here …)

Joining AOMCI has priviledges 🙂

[PugetSoundBoater]

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.

"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson

[PugetSoundBoater]

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.

"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson

[reivertom]

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]

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…

[Author]

Posts