my friends set up has an inline silencer on his ducting, it is quite bulky....
looks kinda like a big version of a baffle box that you would find on a car exhaust, but its made specificly for ducting.

same principal i guess

i would think if your hydro shop cant help you out, you would have to look at industrial air/con suppliers but there are solutions out there.
if you could figure out how they are constructed, im sure you could make a home-brew one without too much hastle.

hope thats of some help
babystarbud Reviewed by babystarbud on . air noise question I'm in the process of moving my growroom. We have a good location for the new one, the only problem is the proximity of a couple of open windows (on warm days) about 30 feet from the growroom. My question is concerning exhaust air noise. I'm going to be using a 1500 cfm fan to exhaust warm air through a window opening. The actual window frame itself is going to be boarded up and I'm making a wood box to surround the open window portion. The wood box will have a 12 inch hole cut in it to mount Rating: 5