Buy some rolls of car audio sound deadening sheets, like Dynamat, and cover your furnace ductwork. Clean the ductwork first and check it for resonance. Cover the spots that vibrate the most.

__________________
Regards

Warren

Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

ENTER > = (HP RPN)

Not part of the in-crowd since 1952.