I've now finished building my Thien baffle dust collector with outdoor exhaust. I also replaced my blower with a new 3 hp blower. Separation seems to work as expected, but I was a bit startled by the sound where the exhaust blows. It's almost like listening to a jet engine starting up. I first thought I needed insulation around the pipe. But it turns out not to be the motor that is loud, but the air turbulence from the pipe.
My design has the blower mounted as high up as possible, with the exhaust pipe leading through the outer wall:
dust_collector_outlet1.png
Worried that the neighbors would complain, or that their horses would panic when I start the dust collector (there's a horse pasture about 10 yards from the exhaust pipe). The horses were further away when I tested today, and they didn't seem to mind the noise.
However, in an attempt to deflect the noise, I made a small "house", with an opening downwards, around the exhaust pipe. The walls were 2" thick with insulation, and hard board on the inside. In an attempt not to add too much resistance to the system, I made the "house" about three times as wide as the pipe (6"). This seems to have worked in deflecting the sound. It's not as noticeable from a distance, but it's still roaring like a jet engine when you stand near the wall:
dust_collector_outlet2.png
I'm now thinking of making a muffler. Any ideas on how to do this?
I thought about drilling holes through the hard board on the inside, into the insulation. Not sure if this will help.
Another idea is to make an extension to the "house", so that the air needs do go further downwards before escaping.
But maybe it would be better to make a real muffler, with a pipe within a pipe and padding in between.