How to Quiet a Noisy Forced Air System

In this video, This Old House plumbing and heating contractor Richard Trethewey explains how to quiet a noisy forced-air system.

Steps for Quieting a Noisy Forced-Air System

Mark the center of start collars on the return and supply side of the heating duct.
Cut holes in sheet metal ducts using a drill fitted with a circle-cutting jig.
Attach start collars to the duct with ¾-inch self-tapping sheet metal screws.
Install bypass damper between the two start collars; fasten damper with sheet metal screws.
Seal seams around start collars with foil tape.
Adjust the counterbalance weight on the bypass damper arm.
Turn on the furnace to ensure the bypass damper opens.