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From: (no name) (no email)
Date: Tue May 01 2007 - 12:44:36 EDT
In a message dated 5/1/07 12:01:03 AM, George writes:
> I am going to insulate my engine room. We have had the boat for 4 years
> and my new 5.5 KW Phasor Generator does not have a sound shield. I like
having
> the generator exposed. It will cost about the same thing to insulate the
> whole engine room as buy a sound box. My question: I have looked at sound
> down and sailing solutions but I am sort of favoring the Glacier Bay sound
> proofing stuff. Does anyone have any tips/ solutions and recommendations.
>
Sound proofing the entire engine room is not a bad idea if you find the main
engine noise annoying. Be aware that the sound proofing process is a lot more
complicated than slapping up a few layers of insulation on the engine room
walls. Most engine sound is structure borne so you will have to use engine
mounts
designed to reduce the transmitted vibration to a minimum. This also means a
flexible connection to the propeller shaft. A surprising amount of sound
escapes through small holes and air ducts. Pass through holes for wires,
cables and
connections must be blocked up with silicone. Air ducts must be internally
insulated with openings directed away from the passenger area. Panels which
resonate at engine vibration frequencies must be stiffened. Overall, the
transmitted sound energy must be attenuated by at least 20 dB before the
perceived
noise level drops to half its former value. That means that the energy in the
hearable sound frequencies outside the compartment must be 1/100 of the energy
inside the compartment.
It is a lot easier to do these things to a small engine box than a larger
engine room. And it ain't cheap. Pat Gerety, former Willard Trawler manager,
told
me that Willard spent $10,000 reducing the noise level on each new Willard 40
trawler - and Willards are by no means whisper quiet.
Larry Z
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