Need help with noise insulation in aluminum hull
 

Guys,

I ahve a 19 ft aluminum boat. It has an inboard jet with a Merc 200 HPO
powerhead. The motor is under a doghouse .. 1/8 aluminum with bubble
wrap insulation.

The motor is very loud. Some noise comes from, the entiure hull
vibrating but most comes from the doghouse which also isnt airtight...

I am planing to line it with soundown dampener and put decoupler foam
over it. ...

Unfortunately I cant get ahold of them by phone or email..

Can anybody please help?

I am wondering how heavy the dampener layer has to be for the 2 stroke
nopise? weight is an issue so I am hopeing .5 - 1 lb/ft2 will do ...

How heavy and think of a foam/decoupler layer will i need? will 0.5
lb/ft2 with 2-3" foam do?

Any advice appreciated :)
Matt

have that on the putside of the doghouse but want some more for the
inside

http://www.auralex.com/sound_isolati...heetblokPL.asp

1#/ft2 as per site. Making it airtight will greatly help reduce noise,
but I am unsure of the fire issues. Sound transmission is affectly
greatly by mass. It may not be the purtiest looking but I bet cement
board would be the most cost effective/fire proof.

Airtight is good, but you do have to move enough air in and out of the box
to keep the engine from slagging down. I don't think the oil and water
cooling are enough especially for accessories like the alternator.

Roger

http://home.earthlink.net/~derbyrm

wrote in message
ups.com...
http://www.auralex.com/sound_isolati...heetblokPL.asp

1#/ft2 as per site. Making it airtight will greatly help reduce noise,
but I am unsure of the fire issues. Sound transmission is affectly
greatly by mass. It may not be the purtiest looking but I bet cement
board would be the most cost effective/fire proof.

Hi
New to here, saw you are looking for a way to reduce noise from your engine
room. There is a system sold that is quite effective but can be a bit high
in price, Sound Down (not the floor under lay) a marine system sold out of
Maine or mass. The system has two layers of high density foam with a thin
sheet of lead laminated between them. The foam laminate is attached to
deckheads, bulkheads and hull surfaces in the engine room. It is then
covered with a perforated aluminum diffuser plate. The purpose of the
diffuser plate is to break up the sound waves before they enter the foam to
be absorbed.
One of the things I think you are looking for is a cost effective way to do
this task, sound down systems would most likely not be the product for you.
If you want to MacGyver a system just make some substitutions and you should
have a good level of success. Any acoustic dampener such as the panels used
in out-door theaters (I believe they are water resistant) attached to the
deckheads or bulkheads covered with a 1/16" aluminum sheet would do the
trick. Space the aluminum sheet 1/8" away from the panel to allow the sound
waves the area the need to disperse. The aluminum plates should have 1/8'
holes drilled on one inch centers or less. The tighter the hole pattern the
better the system will work.
If you are using the system in an area where you have need of a finished
living area surface you can strap over the aluminum and attach your desired
finish surface to the strapping. This type of system can be installed in
just the machinery areas or through out the vessel depending on your need.

Doug
"Roger Derby" wrote in message
ink.net...
Airtight is good, but you do have to move enough air in and out of the box
to keep the engine from slagging down. I don't think the oil and water
cooling are enough especially for accessories like the alternator.

Roger

http://home.earthlink.net/~derbyrm

wrote in message
ups.com...

http://www.auralex.com/sound_isolati...heetblokPL.asp

1#/ft2 as per site. Making it airtight will greatly help reduce noise,
but I am unsure of the fire issues. Sound transmission is affectly
greatly by mass. It may not be the purtiest looking but I bet cement
board would be the most cost effective/fire proof.

Djinning up your own system is a good idea, but lead is MUCH more effective
than aluminum. Steel would also be better. You are looking for mass and
low elasticity so the sound energy gets translated to heat instead of being
transmitted. The last thing you want is a diaphragm which resonates at the
frequency you are trying to damp.

Somewhere in my vast junk pile I have a role of sound dampening material
sold to aircraft owners. It's a tape with a lamination of tar(?) and lead.
Aircraft owners that can afford the weight gain apply it to panels to kill
the vibrations. (Greater mass implies lower frequency implies less pain.
Rumbles are better than screams.)

Roger

http://home.earthlink.net/~derbyrm

"Doug Christie" wrote in message
...
Hi
New to here, saw you are looking for a way to reduce noise from your
engine
room. There is a system sold that is quite effective but can be a bit high
in price, Sound Down (not the floor under lay) a marine system sold out of
Maine or mass. The system has two layers of high density foam with a thin
sheet of lead laminated between them. The foam laminate is attached to
deckheads, bulkheads and hull surfaces in the engine room. It is then
covered with a perforated aluminum diffuser plate. The purpose of the
diffuser plate is to break up the sound waves before they enter the foam
to
be absorbed.
One of the things I think you are looking for is a cost effective way to
do
this task, sound down systems would most likely not be the product for
you.
If you want to MacGyver a system just make some substitutions and you
should
have a good level of success. Any acoustic dampener such as the panels
used
in out-door theaters (I believe they are water resistant) attached to the
deckheads or bulkheads covered with a 1/16" aluminum sheet would do the
trick. Space the aluminum sheet 1/8" away from the panel to allow the
sound
waves the area the need to disperse. The aluminum plates should have 1/8'
holes drilled on one inch centers or less. The tighter the hole pattern
the
better the system will work.
If you are using the system in an area where you have need of a finished
living area surface you can strap over the aluminum and attach your
desired
finish surface to the strapping. This type of system can be installed in
just the machinery areas or through out the vessel depending on your need.

Doug
"Roger Derby" wrote in message
ink.net...
Airtight is good, but you do have to move enough air in and out of the
box
to keep the engine from slagging down. I don't think the oil and water
cooling are enough especially for accessories like the alternator.

wrote in message
ups.com...

http://www.auralex.com/sound_isolati...heetblokPL.asp

1#/ft2 as per site. Making it airtight will greatly help reduce noise,
but I am unsure of the fire issues. Sound transmission is affectly
greatly by mass. It may not be the purtiest looking but I bet cement
board would be the most cost effective/fire proof.

the aluminum is only used as a diffuser plate the sound dampening is
performed by the acoustic panel used, most of which have a lead lining.
"Roger Derby" wrote in message
ink.net...
Djinning up your own system is a good idea, but lead is MUCH more
effective
than aluminum. Steel would also be better. You are looking for mass and
low elasticity so the sound energy gets translated to heat instead of
being
transmitted. The last thing you want is a diaphragm which resonates at
the
frequency you are trying to damp.

Somewhere in my vast junk pile I have a role of sound dampening material
sold to aircraft owners. It's a tape with a lamination of tar(?) and
lead.
Aircraft owners that can afford the weight gain apply it to panels to kill
the vibrations. (Greater mass implies lower frequency implies less pain.
Rumbles are better than screams.)

Roger

http://home.earthlink.net/~derbyrm

"Doug Christie" wrote in message
...
Hi
New to here, saw you are looking for a way to reduce noise from your
engine
room. There is a system sold that is quite effective but can be a bit
high
in price, Sound Down (not the floor under lay) a marine system sold out
of
Maine or mass. The system has two layers of high density foam with a
thin
sheet of lead laminated between them. The foam laminate is attached to
deckheads, bulkheads and hull surfaces in the engine room. It is then
covered with a perforated aluminum diffuser plate. The purpose of the
diffuser plate is to break up the sound waves before they enter the foam
to
be absorbed.
One of the things I think you are looking for is a cost effective way to
do
this task, sound down systems would most likely not be the product for
you.
If you want to MacGyver a system just make some substitutions and you
should
have a good level of success. Any acoustic dampener such as the panels
used
in out-door theaters (I believe they are water resistant) attached to
the
deckheads or bulkheads covered with a 1/16" aluminum sheet would do the
trick. Space the aluminum sheet 1/8" away from the panel to allow the
sound
waves the area the need to disperse. The aluminum plates should have
1/8'
holes drilled on one inch centers or less. The tighter the hole pattern
the
better the system will work.
If you are using the system in an area where you have need of a finished
living area surface you can strap over the aluminum and attach your
desired
finish surface to the strapping. This type of system can be installed in
just the machinery areas or through out the vessel depending on your
need.

Doug
"Roger Derby" wrote in message
ink.net...
Airtight is good, but you do have to move enough air in and out of the
box
to keep the engine from slagging down. I don't think the oil and water
cooling are enough especially for accessories like the alternator.

wrote in message
ups.com...


http://www.auralex.com/sound_isolati...heetblokPL.asp

1#/ft2 as per site. Making it airtight will greatly help reduce
noise,
but I am unsure of the fire issues. Sound transmission is affectly
greatly by mass. It may not be the purtiest looking but I bet cement
board would be the most cost effective/fire proof.