northshore
Well-Known Member
- Jan 17, 2011
- 2,094
- Boat Info
- 1989 340 Sundancer
Raymarine E90W Radar/Chartplotter
- Engines
- Twin 454 Mercruiser 340's
Greetings,
Just a couple of notes from the world of sound and vibration testing where I have spent the last 6 years.
The source of the noise can be transmitted through the structure in which case you need vibration isolation, or transmitted through air in which case you need sound attenuation.
Noises most objectionable to human hearing are normally in the mid to high end of the audible hearing range. For this 'airborne noise' you want to do a sound shield type set up.
If at all possible you want this sound shield to be multiple layers of different densities of materials. Each layer will knock down a certain band of frequencies.
In some of the work we do, a 1/4 high density foam that is on a thick rubber backing is placed around (not bound to) the component making the objectionable noise.
Bad news is the stuff we use is flammable so not good for use in the engine space.
If you can fabricate a container (Starboard - nice and dense) to go around whatever is generating the noise and coat it in 'Lizard Skin' and or Dynamat (SummitRacing.com) inside and out, you will knock the noise back.
A couple of rules of thumb:
Don't hard couple your noise isolation system to what you are trying to make quiet.
You dont have to cover the noise source completely to get rid of the bulk of the noise, just mostly. (like a sound isolation panel between you and the noise source)
Minimize hard reflective surfaces around the noise source where you can.
If you can keep the sound from being transmitted (quieter muffler) its better than trying to isolate it after the fact (noisy muffler and a containment system)
Shoot me a PM if you have any questions of think I might be able to help.
-Mike
Just a couple of notes from the world of sound and vibration testing where I have spent the last 6 years.
The source of the noise can be transmitted through the structure in which case you need vibration isolation, or transmitted through air in which case you need sound attenuation.
Noises most objectionable to human hearing are normally in the mid to high end of the audible hearing range. For this 'airborne noise' you want to do a sound shield type set up.
If at all possible you want this sound shield to be multiple layers of different densities of materials. Each layer will knock down a certain band of frequencies.
In some of the work we do, a 1/4 high density foam that is on a thick rubber backing is placed around (not bound to) the component making the objectionable noise.
Bad news is the stuff we use is flammable so not good for use in the engine space.
If you can fabricate a container (Starboard - nice and dense) to go around whatever is generating the noise and coat it in 'Lizard Skin' and or Dynamat (SummitRacing.com) inside and out, you will knock the noise back.
A couple of rules of thumb:
Don't hard couple your noise isolation system to what you are trying to make quiet.
You dont have to cover the noise source completely to get rid of the bulk of the noise, just mostly. (like a sound isolation panel between you and the noise source)
Minimize hard reflective surfaces around the noise source where you can.
If you can keep the sound from being transmitted (quieter muffler) its better than trying to isolate it after the fact (noisy muffler and a containment system)
Shoot me a PM if you have any questions of think I might be able to help.
-Mike
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