Soundproofing

[LADY JANE]

There have been a few Tugnuts concerned about reducing a boat engine's db's in general. If anything, it's always interesting to see how an original soundproofing design might be revised and improved. For safety's sake, the auto industry has come a long way in this critical area. Although boat engine noise has also been reduced, how might it be lowered even more for an R-21 (etc.) in use today?

 

[rick&sue]

I was hoping a noise expert would respond, since no one has I will give it a try.
Noise control is a science – of which I don’t profess to know anything – other that what has worked for me in industrial applications and on my boat. Noise is like water – it will flow through any openings that you have in an engine compartment. Sealing up all the openings will reduce the amount of noise emanating from the openings. Stopping parts from vibrating (resonating) is another way to reduce noise; the third way is to absorb noise using acoustic foam that has a Mylar cover, and a absorption layer of dense plastic between two layers of acoustic foam. Some of these foams have adhesives that can be attached to flat smooth surfaces. An example is “Quiet Barrier” from Soundproofcow.com Acoustic Foam works great on hatch covers. Adding foam seal between the covers and the deck will also help. Actual hatch cover latches would also help. Another material is a heavy viscus plastic sound deadening material that prevents flat surfaces from resonating. This also comes with a adhesive backing to attach to panels. A combination of all three approaches will be required to reduce the noise from your engine compartment. You can download a decibel meter for your phone to measure the level of sound. These are not very accurate, but will give you a baseline to start from. Your cabin also can be adding to the noise level. Smooth flat surfaces reflect sound, fabrics help absorb sound. The more fabrics and “soft” materials in the cabin the quieter the cabin will be. Hopefully someone who is an expert will read this and make corrections or additions. I can only speak to what has worked for me. Hope this helps.
Rick

 

[NorthernFocus]

By mentioning safety as regards noise, I assume you're referring to hearing protection. If so, the first order of business is to determine whether the noise levels you're experiencing are actually a safety concern or merely annoying. The only way to do so is with a dB meter. They're fairly inexpensive nowadays. A quick internet search will provide plenty of information regarding dB levels and exposure times that are detrimental to long term hearing.

If you do determine that sound suppression is in order, the most reliable method which is also the simplest and cheapest is to wear hearing protection. Foam ear plugs work best when properly used. Many people prefer "ear muffs" because they are re-usable. If you're into technology you may like a noise cancelling set of earphones which can also be connected (wired or wireless) to the VHF or stereo.

If you don't want to be bothered with hearing protection and don't mind the time/cost/effort, then the prior post provided good advice on methods of reducing transmission of engine noise. Just know in advance that while you may achieve noticeable improvement, your expectations will dictate how successful the effort may or may not be.

 

[LADY JANE]

Noise Pollution & Safety....that's a big subject. Hearing protection options are always available to get complete silence, if that's what someone needs at the time. But as we know, any type of deafness can be just as dangerous & unsafe as noise pollution. There's different ways to make it quieter. There are people around us that have much better hearing than we ever did or ever will, and they actually want to stay that way. Our boats really aren't that loud. How many db's does a R-21EC/D1-30F engine actually create at 3000 RPM, & what's the max/safe reading?
-Bill

 

[LADY JANE]

Shoot! "Soundproofcow" is "Not available in the State of California"... Time to go fishing.
-Bill

 

[tlkenyon]

The OSHA limit for noise is 80 dB for an 8-hour day. Above that requires hearing protection in a occupational setting. The law is a lot more complicated, but that is the gist of it. Above 80 dB is not really that loud, but you do not want to be exposed to it for long periods, as fatigue can be enhanced at that level. There are some pretty good iPhone apps to monitor sound levels.

TK