Just had installed a complete Lennox system with variable speed furnace(SL280V). The furnace is indeed much quieter than the dinosaur it replaced, but it seems that when it is running on the slow heat speed, there is a constant whine or "singing" sound from the motor. It seems to run most all the time, and when it does shut off, it sounds like a space ship engine winding down. This can be heard through the register in the master bedroom and I find it aggravating me when trying to sleep. When the motor is spinning down, I can also feel the frequency of the whine in the walls near the unit.
The old furnace had a kind of spongy board underneath it, but my installers said they don't usually use such a board. I am thinking I need some type of vibration absorbent material that the unit can rest on. Any thoughts?