Sound proofing HVAC ducts

Question

We have an HVAC system in our house where the duct work is all sheet metal with no insulation on the interior of the ducts as all of it is buried under inches of foam roofing insulation.

Works great. Efficient air flow with great insulation performance.

The problem is that the pipes carry sound -- conversations, TV, etc.. -- from some vents to other vents. Not very loud, but loud enough to be annoying.

Is there some way to deaden the sound transmission without grossly reducing airflow?

And, of course, do so keeping in mind that all of the duct work is completely inaccessible?

Answer 1

You could try having the ducts Aerosol Duct Sealed. An expensive process not intended for it's acoustical value, but I assume it would offer some.

Reduce noise from forced air furnace. -More related to unit noise then from people, but you still have two basic options: baffles or insulation.

Other options: move the TV so it doesn't shoot at the registers; add a white noise generator; or get new roommates\children.