I've never had a house with air-conditioning before -- this is the
first. I notice that the furnace makes a considerable amount of noise,
of a type I am unfamiliar with. Maybe someone can help me understand
what's going on.

Physical Description of system: forced-air natural gas furnace of the
type I am used to seeing here in Southern California. It has air intake
in the bottom, and hot air comes out the top which goes through
sheet-metal ducting to registers throughout the house. Pretty normal so
far. But above this furnace is another sheet metal box that that round
ducting of the sort that Terry Gilliam put behind the walls in "Brazil"
snaking off somewhere. Outside the house is a 2' x 2' x 3' metal cage
with a circular grille on top and a fearsome-looking fan inside. I
reckon this is some kind of heat exchanger.

Description of noise: With a "normal" furnace I expect to hear the gas
valve open, a soft "whoosh" as the burner ignites and after some 30
seconds or so, the blower kicks in. With /this/ system, the moment I
turn on the heat there is this jet engine whine that starts immediately
and eminates from the furnace closet. The burner lights and after some
30 seconds, the blower turns on. What the heck is the jet engine whine?

--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westphalia: "Mellow Yellow (The Electrical Banana)"
KG6RCR