I want to soundproof a genset located in the bow storage locker of a
catamaran. The genset, which does not have a sound enclosure is
located on a shelf between the hulls with a bulkhead aft and I'll make
a door which will make the enclosed area approximately 3' x 3'x 3'
Cats are weight sensitive anyway and being in the bow the location is
particularly weight sensitive. I have done some preliminary research
on the subject and it seems a sandwich of foam and a dense material,
normally lead or mass loaded vinyl (MLV), is the best sound deadening
combination however the dense material weighs a lot (duh....). 2 lbs
per sq foot for 1/4" seems typical.
I am wondering if anyone has experience with other sound proofing
strategies, techniques or materials that might be lighter? For example
would performated aluminium panels work in this application and be any
lighter?
Does anyone know the effectiveness of MLV, if I halved the thickness
how much increase in sound would I get?

Thanks for you help

Ian