I think I've found the solution to my noise problem with an open return 4-ton AS GAM5 air handler. As many of you may recall, I've been tossing around the idea of replacing a louvered bi-fold door with a solid slab door with a 24x24 filtered return in it.
Not wanting to spend a few hundred bucks on a door, I went to Home Depot and bought myself some 3/4" rigid insulation, a 1/2" piece of soundboard, and the return. I then cut the insulation and the soundboard to fit my air handler closet and installed the return in the insulation.
Here are the sound meter readings:
1) Louvered bi-fold door: 62 dB
2) Insulation/soundboard, return on bottom: 56 dB
3) Insulation/soundboard, return on top: 52 dB
As you can see, I am able to reduce the sound by about 10 dB if I were to put a slab door with some soundboard on the back in place of the louvered door. Since the blower is on the bottom and is the cause of most of the noise, I was wondering if putting the return on top might further muffle the noise from 56 to 52 dB or if that would starve my system for air. I have noticed no whistling or other signs of air starving. Pics below.
So what do you all think? Would it be a bad idea to install a door w/ a return on the top for maximum sound deadening?