Well, Jay just saved my neck. I have 2 built in to the gas furnace (inlet and outlet ) ( at $1400 apiece ), and I checked my noise with them on and off. Sure enough, they were generating about 3 S units of noise on 160. Not surprising since they are computer controlled, and are active even with the furnace not running. Fortunately, I can turn them off with a switch on the control panel. of each. Way to go Jay. 73 Ed