Sound suppression mep004

[SurfinElvis]

Genset installed in an enclosed 10x14 insulated wood-frame building. Exhaust connected to a Maxim silencer mounted outside.
I mounted a K+N style conical filter behind a gable end vent for intake manifold air. Wow, is that a source of some loud noise!

I have louvered openings approximately 24"x24" for fresh air circulation. These are noise sources as they create an opening in the wall through which engine and radiator fan noises pass.

I was planning on installing turn-down hoods over the louvers. Any ideas on design, internal baffles, materials, sound deadening materials, etc?

Anyone running an intake silencer? I have read about them, but have no experience. Really need to quiet down the air intake at the filter. If I can reduce the noise at the fresh air intake, I will likely mount my air filter inside the fresh air inlet, which should help eliminate some of the noise.

Any designs for home-brew stuff would be appreciated. Some of this genset-specific stuff gets a little pricey from commercial dealers...

 

[Triple Jim]

The general principal I use for things like that is to make the sound bounce off sound absorbent material as much as practical. You can get sound absorbing foam and/or fiberglass sheets. The foam with triangular projections works better on lower frequency noise than plain foam, and the bigger the projections, the lower the bottom end of the frequency range of the sound absorption. The configuration you buy will depend on where in the spectrum the majority of noise is. Even flat sound absorbing foam or fiberglass will do a lot of absorbing.

Simple implementations like a hole in the wall for the air intake, covered by a larger plywood panel a few inches away, with foam on the plywood panel, work well. Sound then has to bounce off the foam covered panel before it gets out. More foam on the outside of the wall so that what reflects off the panel has to then face another layer of foam will improve the absorption even more. This will work equally well if placed inside the cutout in the wall if you don't want it on the outside. Ducts with 90 degree bends, lined with foam, are another simple solution. This can work together with the above method. Be creative.

 

[edgephoto]

Auto manufactuers use air boxes that are designed to reduce noise. Maybe find one from a junk yard off a pickup truck to try. I am sure it will come cheap.

 

[SurfinElvis]

After further research, I built an enclosure between the radiator end and the fiberglass louvered opening and used homasote board to create diagonal baffles inside. TripleJim's concept of 90 degree angles, requiring sound to "bounce", worked very well for the circulation air exhaust. A Dodge pickup truck air box is on the way, metal turn-downs being designed for circulation air intake.
Ran the unit for two hours yesterday, about ten minutes on diesel and the rest on WVO. Was running two 3-ton heat pumps, electric dryer and electric oven broiler, every light in the house and a 40 gallon electric water heater...90% load on the genset according to the gauges. Need to hook up a load bank and a meter to make sure the gauges are within range following sewerzuk's conversion, but everything worked perfectly!