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Sound leaking from the ducts... (idea?)

454 Views 5 Replies 5 Participants Last post by  Frank Zimkas
I have taken pains (within a budget) to minimize sound from traveling from my theater. While I have no issues with my door or walls, including outlet holes, I have two large gaping holes called A/C vents. I used what I was given from the builder and am now regretting it.

Is this a loosing battle that can not be won without a great deal of drywall removal duct reworking or will this work....

What if I was to gently compress flexible (insulated) duct work and insert it into the steel existing duct work? The idea being that it would break up the sound a bit. I am not expecting this to solve the issue. I am not that naive. I am just wondering if this would do anything for me or am I grasping at straws?


Thanks in advance!
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Whew, I feel for you.

Is the duct work completely sealed? Can you get to the ducts from some other part of the house? The only think I can think of would be to create some sort of isolated/baffle system.

This only works if you have about 4' x 1' x 2' of space. Basically you need to cut out a section of the solid duct work and insert a long piece of the flexible stuff with several bends in it. This would help a little, but to really make it right it should be a seperate run from the air handler. I assume the sound transmission is through a "shared run" that is in another room?

Ack... Good luck..
I think the easiest thing is what you already mentioned, cutting into the metal ducts and inserting one or more S curves made of flexible ducts. The sound would have to bounce of the flexible sides multiple times. It would be weakened, but not totally blocked.

Another possible method is to build a system of baffles that forces the air to go through through a series of plates with holes. The holes would not line up so the air would have to follow a twisting path. The idea is sort of like a muffler. A couple disadvantages are this would restrict air flow, and would give dust a place to build up.

Of course the best solution in the first place is to have separate heating/cooling systems for the home theater room so there are no shared ducts.
Here's what I'm thinking of doing. I am planning on zoning my heating/cooling system. Each room would have its own ducting run with a damper located mid run. When there is a call for air in the theater it would shut off the ducts to the bedrooms so that at all times there would be a block between the bedrooms and the theater. How well do you think it would work?
Thank you all... I have done some detective work and found that thought the ducts do leak sound the majority of it was coming straight through he floor.

I had a few seams in key areas that had not been sealed up as well as they should/could have been. Once sealed the sound leakage reduced quite a bit. I will still play around with some of the ideas mentioned for ducts.

Thank you very much for your ideas. Yes, simply doing something the right way before the drywall went up would have been the best solution.

Bending Flex-Duct is not a good idea. This type of duct already has a great deal of resistance to air flow which would be compounded by adding bends.

Although Flex-duct has it 's uses, I try to use sheetmetal whenever possible.
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