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Boat Forum / Building / August 2006Sound proofing genset
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 Ian, I have only read about this product, but it is very thin and claims to reduce sound as well as lead does. I have also heard of waterproof (closed cell) carpet underlays that are designed to reduce sound. http://www.acoustiblok.com/marine.html Perforated aluminum on it's own is usually just a cosmetic covering for a more fragile soundproofing. But perhaps someone has a product that has soundproofing and perforated aluminum combined? I looked up a supplier we used to use and they have just such a product called Quietech: http://www.soundown.com/ On my own boat, I just used 3/4" polycyanurate insulation (aluminum foil) finish both sides and covered it with aluminum. It reduced the noise level, but hard to say how much because engine room is open on one side. For the cost of a sheet of this 3/4" material, you could try this at home! BTW - Make sure you provide good ventilation for the engine for engine breathing air and cooling. Another thought - What does Honda use - those units are really quiet! GBM > 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 [quoted text clipped - 16 lines] > > Ian Sound proofing is tough. I went thru a week long symposium some 25 years ago, so I won't mention materials, but: Sound is vibration. If you rigidly bolt the generator to the boat's structure, you'll make the hull/enclosure into the speaker diaphragm. Sure, you can add mass to the panels to make them into poor diaphragms, but it might be easier/cheaper to use better isolation mounts. To do a proper job one has to consider the frequencies being generated and make sure there are no resonators around to amplify the noise. I'd guess Honda spent a lot of man-hours getting their units tamed. I'd guess that most of the sound is generated by the engine exhaust. Can you beef up the muffler? Also, make sure the entire exhaust system is not rigidly bolted to any structure and that it's pointed away from people. Aircraft builder/designers fight this problem all the time. There are various materials one can glue to panels to change their resonant frequency and damp the sound by absorbing the energy, but they all add weight (and cost). (And absorbed energy equals heat.) Roger derbyrm@NOSPAMinsightbbNOSPAM.com http://home.insightbb.com/~derbyrm > Ian, > [quoted text clipped - 46 lines] >> >> Ian Per ian: >I am wondering if anyone has experience with other sound proofing >strategies, techniques or materials that might be lighter? What is your power requirement? If it's 1.6 kw continuous or less, it might pay to get an extra-quiet generator to start with - something like a Honda EU2000. Then you'd have less sound to deaden in the first place.  SignaturePeteCresswell The genset is 14 KW with Kubota prime mover. The reason it is so big is that the boat is hybrid powered. > Per ian: > >I am wondering if anyone has experience with other sound proofing [quoted text clipped - 3 lines] > pay to get an extra-quiet generator to start with - something like a Honda > EU2000. Then you'd have less sound to deaden in the first place. |
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