Generator

To suppress noise through a bricked-up door frame. I coated the bricks with a sound absorbent bitumen paper. Then there was a layer of high density rockwool, then a sheet of chipboard with the inner surface coated with self adhesive bitumen sound absorbent pads. The chipboard was fastened to the bricks using "floating" standoffs designed to stop the transmission of noise to the sheet. Finally there was the old door.

Didn't make a tad of difference to the noise. OTOH Halyard acoustic barrier foam with a lead interlayer solved the problem.

Thanks I'll bear that in mind. I thought it might help in a generator box to stop the sound bouncing around and getting out, much like the wadding in a loudspeaker.

cheers, Pete.