New gas furnace producing resonance in the cold air returns?

[jonny_rizzo]

Anybody know how to fix an issue with a gas furnace producing resonance in the cold air returns?

It sounds much like a tuning fork. When the furnace runs, you can hear this medium-pitch humming in any room that shares a wall with a cold air return. If you put your ear up against this wall, you can hear the resonance very loud and clearly.

The noise is only present around the cold air returns on the 1st and

2nd floor of the house. If you go in the basement and stand next to the furnace, you don't hear it at all.

Now that I think of it, I wonder if its the grills in front of the cold air returns that are "whistling" from the air flowing by and making this noise?

Failing that, are there products that you can use to line the inside of cold air returns to try to prevent resonance?

York Affinity series (93.2%, 60,000 BTU).

[Edwin Pawlowski]

Easy enough to determine. Remove one of the grills and see if it stops. If so, you know what to do, just use a different style. Chances are, the new furnace has a higher air flow. and that can chage the dynamics.

[Bubba]

Even easier..........put you hand lightly on the grilles. You will feel it vibrating if it is. Couple ways to fix it. Slightly bend some of the fins on the grille. It doesnt take much. If you dont want to do that, get some better, more expensive grilles. Most builders buy the cheapest, thinnest grilles made. They resonate a lot. And of course, there is always the thought that the furnace is oversize, fan running too high or the duct work is too small. Bubba