First time poster, long time lurker here.

The AC unit for my rec room is very loud. With the room setup, the return is on the same wall as my TV and main speakers, and when it comes on, I have to turn the volume up to compensate. I had the AC guy come out for another issue, and mentioned the problem to him, and he changed the fan speed, which helped some, but it's still too loud. The unti is in the garage, which is on the other side of the wall, and is very easy to get to. The dust is 14" diameter, and 48" long, and is pretty much a straight shot into the room, except for 1 90* turn where is enters the house. My thought was coming out of the unit and directing the return 90* toward the ceiling, then back down and into the house. Should this help with the noise level? Is there anything else I can do? I haven't measured the sound level, but I'll try to do that tonight. Thanks.

I assume the return duct is a rectangular metal duct? I can tell you what I did with mine, which is to line it with duct liner (e.g., linacoustic). It did reduce the noise fairly effectively. You might also look into replacing the rigid metal duct with a flex duct.

Sorry, mine is a flexable, round duct.

Sorry, mine is a flexible, round duct.

Then I would replace with Flexible Round ACOUSTICAL duct and put a couple of bends as you describe.

Product 6M here:

http://www.flexmasterusa.com/pg/fdpp.php

The difference is the lining. The 6M has a fabric lining that is acoustically somewhat transparent which allows the insulation to do it's thing in absorbing the sound. Your duct may have a metal foil or plastic lining which is not as good in sound control.

The other things you can try is to build DIY serpentine baffle box for the air flow or getting an in-line duct muffler.

Mine was very loud too. Until I put dynamat extreme all over it.

You can see pics and such here.

http://www.avsforum.com/avs-vb/showthread.php?t=1061375&page=2

Then I would replace with Flexible Round ACOUSTICAL duct and put a couple of bends as you describe.

Product 6M here:


The difference is the lining. The 6M has a fabric lining that is acoustically somewhat transparent which allows the insulation to do it's thing in absorbing the sound. Your duct may have a metal foil or plastic lining which is not as good in sound control.

The other things you can try is to build DIY serpentine baffle box for the air flow or getting an in-line duct muffler.

My duct work is from the contractor special line. :( Which Acoustical line is the better one? There is a dealer in my city, but do you have an idea per foot, before I get sticker shock.

My duct work is from the contractor special line. :( Which Acoustical line is the better one? There is a dealer in my city, but do you have an idea per foot, before I get sticker shock.

Of course I discovered that product After my system was built. From past reports here of guys who used it, it is 2x to 3x the cost of HD flex duct. Of the two products if you read the linked data sheets the 6M is has a broader band absorption characteristic then the 8M.

Thanks for the help, I will call the local dealer and see how much Christmas money I need to stash away for this. :)