Sugguestions reducing engine noise

patrscoe

Member III
I like to investigate into methods of reducing engine noise on my Universal. Engine runs good and I have sound insulation in the compartment but you can definetely tell a Universal engine in a sailboat from the noise at the exhaust.
There is a Ericson and Catanlina down the dock with a similar engine and noise.
Any sugguestions on methods of reducing noise?
 

patrscoe

Member III
Thanks - I will review.
I do have insulation in my compartment. Perhaps there are voids or upgrades I need to make.
I am also going to invest into a light air sail to help reduce the urge of running the engine.
I am still figuring that out.
 

jtsai

Member II
Christian, interesting that the small access door to raw water stainer on your 38 is hinged to the companionway ladder side. Won't it be better if it swings and lay flat against the stove? My 32-3 is that way,
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
If you look at my photos in our blog, from when the engine compartment was totally re-insulated, note the similarities to what Christian did for his boat. Worth noting also is his use of the word "suppression" rather than ellimination. There are vibrations and 'noise' from across a spectrum of sound to try and attenuate. I did not use the two layer foam with the "decoupling" layer, but kind of wish that I had.

Problem is not that our new engine is noisy (it is gratifyingly quieter than the old one) but that all diesels make a lot of noise.

Also, IF you have any small openings or cracks along the edges of the engine panels or front 'box', noise will leak out. Those vibrations/sounds just "want to be free"... :(
I have visited aboard new vessels with thick rubber gaskets around the access to the doors/openings to their engines, and this is likely why.

An example is the open structure behind the engine that communicates with the lazaretto and aft cabin or quarter berth paneling. We notice the difference when the large aft berth cushion is in place rather than out of the boat.
ALL the effort is worth while, but to some extent it will always be a "game of inches".

Aside: when I operate our club's dredge with a 250 hp Cat diesel, from inside the insulated cab, I and the other operators wear thick ear protection. Outside on the side deck the roar at 2000 rpm is rather impressive albeit tiring.
(Heat and exhaust are not the only waste products from these hard working engines -- also sound energy.)
 
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goldenstate

Sustaining Member
Blogs Author
Thanks - I will review.
I do have insulation in my compartment. Perhaps there are voids or upgrades I need to make.
I am also going to invest into a light air sail to help reduce the urge of running the engine.
I am still figuring that out.
I'm not sure if there is a magic answer when one is dealing with 30+ year old engines. The new Beneteaus (cue harangue about how new Beneteaus are poorly built etc.) in my marina do seem much quieter than my boat, but all of the other similar-vintage boats around me burble and chug with a sound similar to my own engine... We may have to live with it to some degree.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
small access door

Yes, swings the wrong way. I have been trying to talk to the guy who installed it at the factory, but he's still out to lunch.

Here's the ultimate solution to diesel noise:

noise suppression.JPG
 

Mark F

Contributing Partner
Blogs Author
Sorry I couldn’t resist ;-)
 

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peaman

Member III
Here's the ultimate solution to diesel noise:

noise suppression.JPG
That is pretty much it on boats like ours. It's pretty easy to attenuate higher frequencies, because they carry less energy. Some foam, or foam plus loaded vinyl (that's what the sound deadening stuff is) is enough to make a noticeable improvement. Lower frequencies carry more energy, and tend to energize larger surfaces, so they are much more difficult. An engine running at 2400 rpm has a primary frequency of only 40 Hz. Best solution is to add mass between source and receiver (you). But maybe worst of all is that since noise travels through air, air leaks in an attenuating surface are surprisingly detrimental to the performance of the attenuation system. Big yachts can use thick insulated panels, weatherstripped engine room doors, and even attenuating baffles and other tricks in necessary air passages. But since my engine space is actually connected to my starboard cockpit locker, there really is not much I can do to reduce noise. I did replace the acoustic foam on the engine cover, as much for aesthetics as anything. But my main means of noise reduction is either to lower the rpms, or shut down the noise source entirely, and enjoy the silence.
 
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