How to reduce noise from HVAC return? - AVS Forum
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post #1 of 5 Old 08-30-2009, 11:23 AM - Thread Starter
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I'm trying to improve the acoustics of my 24x16' home theater room.

The first problem I'm tackling is to reduce noise from the HVAC unit, which is located directly on the other side of the left wall. My current plan is to put up either one or two layers of 5/8" drywall with Green Glue on that wall.

However, the left wall also contains a 30x16" HVAC return, a few feet from the corner with the screen wall. The drywall/GG should attenuate lower frequencies, but the return makes a fair amount of air noise, sometimes causing me to increase volume if the HVAC unit comes on during quiet dialogue. Moving the return is not possible.

My first thought was to build an external baffle, something like a drywall/Green Glue sandwich framed by wood? This would be slightly larger than the return and serve to block the direct sound. It would be offset far enough from the wall for adequate airflow around it. The HVAC filter is located elsewhere, so I don't need access to the return. This would also allow me to remove the metal grille, which might reduce noise a bit more.

Is there a better way? I imagine my wife is not going to like that protuberance on the wall. I suppose I could put one of my 28x41 poster frames over it, although I'm not sure how that will look.

Another idea is something like this, does anyone have any experience with these grille silencers?
http://www.mfmca.com/storefront/p-32-16-wide-units.aspx
http://acousticstandards.com/acousti...cersgrille.cfm
http://www.aerosonics.com/catalog/GRILLE.PDF

I'm not at all concerned with keeping HT noise in, only reducing HVAC noise to a reasonable level inside the theater.

Also, I'm not married to any of these ideas (but hope to remain married to my wife after this is done ). I bought a case of Green Glue, but that's all I've done so far. I have a highly skilled carpenter friend helping me.

Any advice greatly appreciated.

Thanks,
Bob
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post #2 of 5 Old 08-30-2009, 12:20 PM
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some items, Line all the interior surfaces of the return with JM Linacoustic RC or equivalent. Also the area in the bottom of the furnace around the fan may benefit from some Linacoustic. If there is a lot of vibration of the metal furnace walls which contribute to the sound, attaching a couple layers of Dyna-mat Extreme will help tame it.

If you could post a picture of the return it might generate other thoughts. Also a shot of the Furnace. Take one with the lower cover off.
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post #3 of 5 Old 08-30-2009, 02:38 PM - Thread Starter
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Quote:
Originally Posted by BIGmouthinDC View Post

some items, Line all the interior surfaces of the return with JM Linacoustic RC or equivalent. Also the area in the bottom of the furnace around the fan may benefit from some Linacoustic. If there is a lot of vibration of the metal furnace walls which contribute to the sound, attaching a couple layers of Dyna-mat Extreme will help tame it.

Thanks for the suggestions, very helpful. The return is already completely lined, not sure how the material compares with genuine Linacoustic, though.

The HVAC blower is quite noisy, and I was planning to add lining to the enclosure, which currently has none on the bottom or removable cover. Dynamat is a really good idea too. I've attached a photo of the HVAC blower enclosure, that was as far back as I could get.

I'm also planning to add a layer of MDF and Green Glue to the furnace room door, since some noise comes down a hall and into the theater from that direction too.

Quote:


If you could post a picture of the return it might generate other thoughts. Also a shot of the Furnace. Take one with the lower cover off.

I knew the first reply would ask for photos. Unfortunately I have a large piece of furniture in front of the return, which I can't move at the moment. It will be going away soon, but it's how I've been taming the noise up to now.

But what I'm really looking for is a way to prevent noise from the return from going straight to my ears.
LL
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post #4 of 5 Old 08-30-2009, 02:57 PM
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I looked at that pic and some linacoustic inside the cabinet and maybe even Dyna-mat on the blower housing might have some benefit. However keep in mind I am not a HVAC expert.

I also wonder about rubber isolation mounts for the blower motor but I have no idea if that is possible.

Some time ago there was a guy who had a similar situation in the main room of his condo. The HVAC was located on the other side of wall in his main TV area with the main return in direct view of his seating location. One component of his strategy was to put a bookcase in front of the main return set out a few inches. He put a layer of duct liner on the back of the bookcase and reported that he did tame the sound that made it to his listen location in the room.
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post #5 of 5 Old 08-30-2009, 03:34 PM - Thread Starter
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Quote:
Originally Posted by BIGmouthinDC View Post

Some time ago there was a guy who had a similar situation in the main room of his condo. The HVAC was located on the other side of wall in his main TV area with the main return in direct view of his seating location. One component of his strategy was to put a bookcase in front of the main return set out a few inches. He put a layer of duct liner on the back of the bookcase and reported that he did tame the sound that made it to his listen location in the room.

Maybe that's the thing to do, buy a tall bookshelf instead of trying to build something permanent. I do need more storage space for discs.
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