We have a booster fan built-in to a 8 inch round duct. This was
needed for the long run, 50+ foot. It has a rheostat for speed
adjustment. Seems to move the air just fine at 60% of full
power. Problem is the noise. When the air is moving the noise
travels to all the rooms. We did replace it, thinking the first
one was defected. Does anyone know of a quiet booster fan?

Thanks,
TP