*Update*

I was reworking the exhaust ducting, to tuck it up in the joist bays, and I discovered that the exhaust muffler doesn't really do anything, now that an intake muffler is in place. The bulk of the noise seems to be generated at the intake; once you silence that, you're golden.

So I'm leaving the intake muffler in place, and using the second muffler to quiet the intake of the inline fan I'm about to mount to cool the HPS lighting.

Live and learn. :smokin:
cavadge Reviewed by cavadge on . Fan noise, sound proofing Has any one used heat/ac duct as wall covering, you know the kind that folds up into those square ducts? Mylar on one side yellow fiberglass insulation on the other about 1" thick. My grow room is completely sealed up from the rest of my house secret door etc. I do get some smell I think from opening the door. But,y problem is noise, odd fan like noise coming from a wall in the bathroom, can't hear it over the bathroom fan but when it's not on there is noticeable noise from the room. I Rating: 5