Noise abatement for standby generator

[onetwothree]

Need suggestions or solution to reduce sound emissions for a "Generac" liquid cooled gas engine generator QT080. The sound emissions in dBA at normal operation at 7meters is 74dBA. Problem is noise ordinance is not to exceed 60dBA at property line. The generator is within 15 feet of property line. Generator can not be moved. Limited budget and any modification to the generator would negate the warranty.

 

[GregLocock]

60 dBA at 5m is a big ask

Build a concrete box around it and direct the intake and exhaust openings away from the property line. Use baffle type openings so that you cannot see the engine from the outside.

Add some rockwool insulation (fire hazard) to get rid of high frequencies.

Rinse and repeat as necessary, building a russian doll of concret boxes

Direct the intake and exhaust into a truck silencer via a flexible coupling.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[SylvestreW]

So, the constraints are
1) 60 dBA @ fence line
2) Can't move nor modify generator
3) Can't spend much

You say it's normally 74 dBA @ 7m so at fence line it's around 78 dBA. You then need ~17dB reduction in the form of an enclosure w/ silencers etc. There's air flow (both for engine and heat transfer) to consider.

Quite frankly, Greg's suggestion is about all you have left to consider, but even that won't be cheap.


-
Aercoustics.com

 

[gr2vessels]

In a similar situation, the new neighbour has threatened us with legal action if not silencing the noisy stand-by generator, down to 45 dBa at the fence line, 6m away. We cut of the bottom of a 20 ft container, welded anchor lugs, padded the walls and roof with some acoustic insulation pads (drilling holes in the wall), penetration on the roof for the exhaust + new muffler, noise attenuated air intake on top, exhaust fan on the other end with some air outlet silencer, some cabling with glands. Kept one front access for maintenance. However, the engineering manager grabbed his chest when he saw the bill.
cheers,
gr2vessels

 

[BigBoyMcCoy]

Have you acquired full octave frequency pressure levels from the system to get a better understanding of the major acoustic culprits? By the sound of it (no pun intended), there is an alternator with a mag shaft spinning at some RPM (providing a 1X and 2X RPM acoustic frequency) as well as the combustion frequency (probably around 500 hz). You can shield the higher frequencies fairly easily, however, the lower frequency combustion noise will probably need to be dampened via a muffler/silencer. I recommend finding what your peak frequencies are as well as analyzing the frequency pressure levels relative to their A-weighting to see what frequencies are hurting you most. Honestly, a 17 dB drop is all but impossible though