A tip which may help some:

I am using an inline (axial I suppose) fan with the carbon filter for ventilation and odor control. I mounted it to the floor joists above with the supplied bracket, plugged it in, and went upstairs.

Sounded like a lawn mower running in the room above. Vibration was being transferred to the framing of the house. Did a search and found these antivibration mounts, perfect for ceiling mounting - Vibration Mounts eStore Cylindrical Rubber Anti Vibration Mounts Rubber Neoprene Urethane Sorbothane Silicone Gel Ring Mounts. Click on the pic for steel mounts with rubber, rated to 110 lbs. I ordered the unthreaded units rated for 25 lbs. Problem solved. I still feel a little vibration if I lay on the floor above, but no noise.

HTH,
Cav