Sound from my home theater in the basement travels into my son's bedroom via the HVAC vent (my wife heard him up last night at 8:30 -- he goes to sleep at 7:00 PM -- and she could hear sounds through the vent next to his bed). My son said "daddy in the movie theater"?

Obviously this is not good.

The theater room is two floors below my son's bedroom. My HVAC system is complex, with two main trunks going through the ceiling of the theater room --one for the main floor/basement combined; and the other for the bedroom level. The house is split into two zones via an electronic damper (one system). There is also a third trunk in the ceiling for return air.

I assume the sound is getting into the main trunk for the bedroom level -- then traveling through the vents? Funny thing is, I don't hear it in all vents -- it seems to be worse in my son's bedroom. If it got into the main trunk, why wouldn't I hear it from all vents on the bedroom level?

And for that matter, with the main trunk for the basement/main floor also going through the home theater room, why don't I hear it in every vent throughout the house?

It doesn't make any sense that it would be primarily in one vent.

So how do I stop this? Luckily, as you can see from the pics in my signature, there is a drop ceiling in the basement, so the ductwork is accessible.

And here are pictures of the ductwork in the theater room, prior to the drop ceiling going in:

http://ericbeth.home.comcast.net/~ericbeth/media2.jpg

http://ericbeth.home.comcast.net/~ericbeth/media1.jpg

So what can be done to this ductwork to stop the sound going to my son's bedroom vent?

Last week:

http://www.avsforum.com/avs-vb/showthread.php?t=974472

Last week:

http://www.avsforum.com/avs-vb/showthread.php?t=974472

I saw that, but it doesn't really help me -- as I'm not a DIY guy (which is what I thought that was referring to). And it seemed like it applied to a different type of ductwork (mine isn't the round stuff). I also didnt' really understand the recommended solutions.

This home is new construction, not yet a year old, so I need a solution that can be implemented in existing ductwork -- and hopefully can be performed by an HVAC company (maybe the one the builder hired for the home).

By the way, here are pictures of the ductwork in the theater room (prior to the drop ceiling going in). I believe the trunk on the left is for the bedroom levels, the one in the middle for the basement/main level and the one on the right for the returns.

Looking at these pictures -- any ideas as to what can be done:

http://ericbeth.home.comcast.net/~ericbeth/media2.jpg

http://ericbeth.home.comcast.net/~ericbeth/media1.jpg

No one has any good suggestions?

Have an HVAC company come by to assess the feasability of adding fiberglass duct liner to the insides of the metal ducts.

Regards,
Terry

Are you sure it's the ductwork? Sometimes these mysteries are a narrowing down process. Perhaps you could get a portable sound source like a small radio and move it from point to point above your ceiling. See if you can determine a possible hot spot.

Another consideration is that it could be a chase that the duct is in rather than the duct itself. Might explain why you don't hear it all over.

Lastly, your son's room may simply have fewer bends and turns = less diffusion of the sound on its way up.

Hard to say, obviously. You should play around before committing to cash outlay.

Have an HVAC company come by to assess the feasability of adding fiberglass duct liner to the insides of the metal ducts.

Regards,
Terry

I've read about duct liners -- but I am skeptical. Will they really do anything? After all, if air can move through the ducts, wouldn't sound move through them as well. Or does the liner block the sound from the theater from going through the ceiling tile then into the trunk lines?

Have duct liners been known to actually work 100% in my situation?

I imagine that they would have to take down the ductwork in the theater room; add the liner and reinstall the duct work. That sounds pricey too.

I'm sure anything can be done for a price.

Are you sure it's the ductwork? Sometimes these mysteries are a narrowing down process. Perhaps you could get a portable sound source like a small radio and move it from point to point above your ceiling. See if you can determine a possible hot spot.

Another consideration is that it could be a chase that the duct is in rather than the duct itself. Might explain why you don't hear it all over.

Lastly, your son's room may simply have fewer bends and turns = less diffusion of the sound on its way up.

Hard to say, obviously. You should play around before committing to cash outlay.

Well if it isn't the ductwork, why would the sound come through the supply vent in my son's bedroom? Its not coming through the house or the walls -- its the supply vent on the floor in his bedroom. You can hear it clearly through there.

I have a similar problem and think I might have a solution.

To give some background - I use to do custom car stereos. To reduce rattles caused by vibrations you install sound damping material. I am researching if this can be used directly ont he outside of the tin vents.

If it can - then it will stop vibrations and sound transmissions. Around the vent we are also using fiberglass insulation and 2 layers of 5/8 drywall with green glue. The drywall will be decoupled from the ceiling studs.

I am thinking of using a bit of the sound dampening on the inside of the vents as far back as I can reach.

Did you find a solution?

I had the exact same problem. A week after we moved in to our new house, i tested the proposed home theater area with just a radio. 2 floors up, you could heard it very much through the ductwork in both the main and kids bedrooms....and this was just a radio. I got on here and started reading up. When it came time to build, here is what I did...and it was all pretty easy.

1) replaced the individual ducts that ran through the theater area with flex duct. We ended up having to replace 3 runs and it wasn't that big of a deal as the area was still unfinished.

2) added a "rubber boot" to the end of the main duct line that ran through the theater to back the the air handler. This effectively breaks up the metal soundpath from the theater duct and the rest of the house.

3) Put up sound dampening sheets on the exposed areaa of the main trunk in the theater. Car guys use these. I found them pretty cheap at Parts Express
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=268-030

4) Green Glue with double drywall on the soffit around the main trunk.


After the drywall w/ green glue was up, I pulled in the amps and speakers to test all of the speaker wire runs. I put in the beginning of Blade 2 and cranked it up as loud as I could stand it in the theater. Went upstairs and pressed my ear to the vents and nothing. Mission accomplished.