If the heat pump makes rattling noises when it runs, be sure the cover panels are screwed on tight. If they aren't, tighten them. Other noises may be coming from squealing belts or rattling ductwork.

Squealing sounds from a forced-air heat pump generally occur when the belt that connects the motor to the fan slips. If the blower is making a grinding noise, shut off the unit and call a heat-pump repair technician--the motor's bearings are probably shot. In most cases, however, the belt is improperly aligned or worn and needs replacement. Follow the instructions in your owner's manual.

This job involves removing the access panel, loosening a couple of bolts that hold the blower motor at the proper tension, and realigning or adjusting the belt. In many cases it's a good idea to remove it and buy a replacement. When reinstalling the belt, be careful not to overtighten it as this can wear out the motor bearings.

Many heating ducts are metal, so they conduct noise quite readily from the air-handling unit to your rooms. To break the conduction of sound, you can have a heating contractor insert flexible insulation ductwork between the heat pump and the ductwork runs.

If you hear a pinging or popping sound coming from the ductwork, this may be caused by thermal expansion or by air blowing past a loose flap of metal. Track along the duct runs, listening for the sound. If you find it, make a small dent in the sheet metal to provide a more rigid surface that's less likely to move as it heats and cools.