Thanks.
Much of furnace noise has to do with the installation too. I've heard of someone putting a rubber (or other material) isolation band between the furnace and main in/out ducts, so that funace vibration is not transmitted down the ducts. Also branch ducts can be flared differently to lessen noise. Wrapping ducts in rigid fiberglass, rubber pads under the furnace feet to stop noise trasmission. Or even just soundproofing the furnace room itself. But it should all start with a quiet unit to begin with. I do music recording in my home studio and quiet would be nice.