Sound Traveling Through HVAC Duct to Bedroom -- what can I do? - AVS Forum
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post #1 of 21 Old 01-16-2008, 06:51 AM - Thread Starter
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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:





So what can be done to this ductwork to stop the sound going to my son's bedroom vent?
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post #2 of 21 Old 01-16-2008, 07:42 AM
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Last week:

http://www.avsforum.com/avs-vb/showthread.php?t=974472
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post #3 of 21 Old 01-16-2008, 07:49 AM - Thread Starter
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Quote:
Originally Posted by BIGmouthinDC View Post

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:



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post #4 of 21 Old 01-16-2008, 10:15 AM - Thread Starter
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No one has any good suggestions?
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post #5 of 21 Old 01-16-2008, 10:26 AM
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Have an HVAC company come by to assess the feasability of adding fiberglass duct liner to the insides of the metal ducts.

Regards,
Terry

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post #6 of 21 Old 01-16-2008, 10:28 AM
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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.

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post #7 of 21 Old 01-16-2008, 10:34 AM - Thread Starter
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Quote:
Originally Posted by Terry Montlick View Post

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.
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post #8 of 21 Old 01-16-2008, 10:35 AM - Thread Starter
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Quote:
Originally Posted by Ted White View Post

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.
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post #9 of 21 Old 06-03-2008, 07:32 PM
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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?
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post #10 of 21 Old 06-04-2008, 04:39 AM
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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/showd...number=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.

I don't really like talking about my flair

My Home Theater Project:
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post #11 of 21 Old 08-22-2012, 09:42 PM
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A I lay in my bed i recall when i was a teen hearing my older brotherplaying his loud music 3 w floors up. It drove me crazy , . He joined the army and that took care of that. Now 35 years later ,i founs my self living wit him because of my mrdical conditions.He has a large very nice theater romm and residence in the basement .
Who would have ever guessed 35 years later that i would be trying to sleep to that sameBOOM BA BOOM EVERY NIGHT ,ALL NIGHT AGAIN ??? THE BEST WAY TO STOP THE NOISE IS SOME NICE QUALITY HEAD SETS TO USE AFTER 7PM ,BECAUSE HE IS YOUR SON . I could almost guarntee ,if he is disturbed by the sound now ,it will build up a resentment that he will have a hard time to let go of in later years. I tell you from experience. Its a win win solution . You get to have some new toys and yoir son gets lots of nice restfull,healthful sleep .. Its the reverse here ,i have to wear earplugs and listen to music till about 3am to not hear the Boom. "FRANK IF YOU SEE THIS ITS KILLING ME," PLEAS HAVE SOME MERCY AFTER 10 PM.
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post #12 of 21 Old 08-23-2012, 04:42 AM
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LOL

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post #13 of 21 Old 08-23-2012, 04:56 AM
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Joevig

great post

if anyone needs headphones, please join us here: http://www.avsforum.com/t/1245475/headphone-audiophiles
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post #14 of 21 Old 12-05-2012, 12:11 AM
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Do you think putting a sound panel over the vent would work ?
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post #15 of 21 Old 12-05-2012, 06:11 AM
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Quote:
Do you think putting a sound panel over the vent would work ?
No and the other side effects would not be pleasant.

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post #16 of 21 Old 12-05-2012, 06:21 AM
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Whst if I put the sound panel over the vent in the bedroom?

It's very low so there has to be something little I can do.

The first floor it's blasting and that I don't care it's just the bedroom upstairs
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post #17 of 21 Old 10-09-2013, 04:41 AM
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I'm currently having the same issue of sound traveling up the ductwork from my basement to a bedroom. Found this stuff while searching for solutions but I'm not sure if it'd do the job. Has anyone ever used AudioSeal pipe and duct wrap, or anything similar? This site also had SoundVac duct liner that looks like it may do the trick, but I'd hate to pull the trigger if I'm not sure

http://www.acousticalsolutions.com/uploads/202161377633286.pdf

http://www.acousticalsolutions.com/soundvac-duct-liner

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post #18 of 21 Old 10-09-2013, 04:47 AM
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You need duct liner. but the variety you posted is very expensive compared to what I use. Also do you have access to the ducts for a retrofit? more information needed about your basement construction and your ducts.

Replacing metal ducts with flex can also be a cure.
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post #19 of 21 Old 10-09-2013, 05:31 AM
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Thanks for the quick reply. Yes, it's a clean slate in terms of having access. What type of duct liner did you use and where did you get it? Is that a simple DIY job or think I should leave this to a pro?

We are at the beginning stages of remodeling the basement, so now is definitely the time to make changes so that I can enjoy the theater while everybody else sleeps upstairs! My speakers will be set up directly below the ducts and alongside a staircase that is rather resonant. I'm wondering if some sort of insulation under the stairs may also help reduce unwanted noise

Here's what I'm dealing with.

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post #20 of 21 Old 10-10-2013, 10:01 AM
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OK, since you are at beginning stages you need to do some reading on the topic of soundproofing. Soundproofingcompany.com has some very valuable articles on vaious topics.

Those big metal trunks are very common in forced air systems. Yes duct liner can be added but unless you have the skills to take apart and reassemble a pro would be better. Retrofitting the large trunks is not that common but would be useful. You could attack just the areas you can reach from each end and that may put a dent on the sound transmission. I have a current project where the original builder used Lined trunks for many areas of the house and it is dead quiet.

Having said that there are two strategies most often used for dedicated theaters:

First build a theater room that keeps the sound from ever getting to the ducts in the first place. You will need a soundproofed soffit containing the ducts.
Second the supply and return ducts connecting the theater to those trunks should be flexible insulated ducts not metal. Longer runs and a couple of bends help.

Looking at the picture, that vent cut into the trunk (above the black jacket) is like cutting a hole in the floor. Sound enters there and is transmitted to the vents upstairs via the ducts.
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post #21 of 21 Old 10-23-2013, 11:13 AM
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Thanks so much for the response and advice! I'm currently having trouble convincing my HVAC guy to use lining because he's never heard of using duct liner for such a purpose. Grrrrrrr! Either he'll come around or I'll be looking for another HVAC professional! Anyway, I'll be sure to follow your suggestions as best as I can and will update you once they've been implemented.

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