Air ducts are noisy

Most folks when talking about noise means it's coming from the return air or intake. Is this correct? Please advise. RepairUSA

Many heating/cooling 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 heating/cooling system 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.

If your air ducts are metal then there will be a certain amount of expanding and contracting because of the temperture constantly changing as the unit kicks on and off. Even if you had your metal replaced with plastic or fiber there is still expanding and contracting as the unit kicks on and off. Insulating your attic and your ducts with heavier insulation can reduce noise somewhat. Not to mention giving you more protection.