I installed one for a temp cabinet shop about six months ago. Our unit was very straight forward but weighed in at 650lbs. The noise from this unit was comparable if not quieter then a large fan or winch motor. When under heavy load it made a little more noise.
You should get your hands on some spec sheets or ask the manufacturer what the decibel level is. Once you know that you can check on line to see what it compares to (i.e. vacuum, car engine, whisper, copier, etc)
I'm sure it can be safely installed above a t-bar ceiling but you must be absolutely sure it is securely mounted and that the ambient temperatures above ceiling are not above manufactures limits. A call to the manufacturer will answer that question also.
I should mention I mean a large fan and not an industrial sized fan. You could easily stand next to it and hold a conversation.
[This message has been edited by Local (edited 05-04-2005).]