Air-conditioning and heating systems produce noise that travels through the air ducts. Depending on how close you are to the fans of the air conditioning system, you can hear the sounds of the fan pushing the air through the ducts. There are many ways of reducing noise through the duct work, but the easiest and most effective method without restricting airflow is installing an in-line noise muffler. The in-line noise muffler will not only reduce the noise from the fan but noise from other rooms that travels through the ducts.
Turn off the air conditioning system at the thermostat.
Climb into the attic and locate the duct work with the noise problem. The easiest way to identify the duct work is to stand over the room where the duct produces the noise, and locate the duct work going into the room. Some homes have their duct work in the basement; if this is the case, then locate it via the basement.
Measure the size of the in-line noise muffler with the tape measure. Proceed to mark the length of the in-line noise muffler on the existing duct.
Cut the length of the in-line noise muffler off the ducts as marked with the aviation snips. Try to cut as straight as possible to make the installation easier.
Insert the in-line noise muffler into one end of the ducts and secure it with the sheet metal screws. Pull the other end of the duct into the other end of the in-line noise muffler and secure it in place with screws.
Turn on the air-conditioning system and inspect the in-line noise muffler and the ducts for any leaks. If you notice any leaks, wrap the connections with duct tape.