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JayBird 07-18-2012 10:41 PM

Sound proofing HVAC return duct
 
I'm about to have a sound proofing liner installed in my HVAC return duct. My return is a little undersized and I simply cannot take the air noise any longer. The return is above my recliner and I'm limited in options of where I can relocate it.

I'm having the same return duct enlarged in the basement because it's exposed but in side the drywalled chase will remain the same with the exception of enlarging the opening behind the grill. HVAC tech is also going to line the new duct with a HVAC sound proofing liner and the duct in the chase as far he can reach. This is my cheapest and easiest option to make an improvement.

Anyone know anything about the this "liner"? Does it help with air noise? There is no buckle sound just loud inrush of air.

scottmcd9999 07-19-2012 04:42 AM

There's all sorts of soundproofing material so you'd have to be more specific. Also, you'd have to determine what is causing the air noise - if, for example, the blower system is just a few feet from the return in a direct line, then no amount of soundproofing is going to help.

Ultimately the cause it improper duct design, of course. A return that is properly installed and sized should not be overly noisy. If you could increase the ENTIRE size of the duct, or add a second return, you might find that to be a better solution.

beenthere 07-19-2012 04:45 AM

Could end up louder.

Add a return, that has its own duct back to the unit.

biggles 07-19-2012 06:43 AM

definitly adding a return back to the units plenium will relieve the return noise.sit in your chair there and have somebody just crack the access panel on the fan to hear the noise change as they pinch the panel ever so slightly...away

JayBird 07-19-2012 09:33 AM

Quote:

Originally Posted by scottmcd9999 (Post 969259)
There's all sorts of soundproofing material so you'd have to be more specific. Also, you'd have to determine what is causing the air noise - if, for example, the blower system is just a few feet from the return in a direct line, then no amount of soundproofing is going to help.

Ultimately the cause it improper duct design, of course. A return that is properly installed and sized should not be overly noisy. If you could increase the ENTIRE size of the duct, or add a second return, you might find that to be a better solution.

I don't know what kind of material their using. They are calling it "internal sound lining"

The return goes down the chase behind me and the furnace/blower unit is directly below me in the basement. So I guess you can say its in a direct line.

JayBird 07-19-2012 09:37 AM

Quote:

Originally Posted by biggles (Post 969315)
definitly adding a return back to the units plenium will relieve the return noise.sit in your chair there and have somebody just crack the access panel on the fan to hear the noise change as they pinch the panel ever so slightly...away


There is a second return punched in the bottom of the unit right next to the blower. No ducting, just filter. On the other side of the unit the return ducting comes in. They are also adding about a 4 inch extension to the side with the just the filter, hopefully quieting that down some as well.

The unit is big in my opinion furnace is 125,000 BTU and the fan is big, I want to say 1700 CFM's but not 100% sure. Fan speed is low as it goes on LOW/MED but its still got a lot of turbulence.

tima2381 07-19-2012 10:07 AM

Quote:

Originally Posted by scottmcd9999 (Post 969259)
There's all sorts of soundproofing material so you'd have to be more specific. Also, you'd have to determine what is causing the air noise - if, for example, the blower system is just a few feet from the return in a direct line, then no amount of soundproofing is going to help.

Ultimately the cause it improper duct design, of course. A return that is properly installed and sized should not be overly noisy. If you could increase the ENTIRE size of the duct, or add a second return, you might find that to be a better solution.

Most houses here have a single return in a hallway with the blower just a few feet away, and it's rather loud. Mine measures 57 dBA / 66 dBC at 1 meter. In a room off that hallway, when a TV or stereo is at a low but still reasonable volume, I have to turn it up when the blower kicks in. How does everyone define "overly noisy"?

techpappy 07-25-2012 09:49 AM

The return air is too close to the furnace as is your chair. Suggest you temporarily block off the return at the ceiling, remove the fan compartment door and run blower to see if sound is still too loud or not. If it is, then, soundproofing the duct may not be the answer. I would try to relocate the return to another area of the house OR from two areas of the house away from your chair/TV room. Adding sound insulation will reduce the return air duct thereby increasing the velocity/noise. May create hissing at grill. Not a good idea in my books. Get rid of the problem. Relocate the return air.

JayBird 07-27-2012 12:25 AM

Well I had the portion of the duct that is accessible in the basement enlarged and sound lined. HUGE difference in sound. Much much quieter and quite frankly I don't need to crank up the tv anymore. The old duct was "L" shaped from the basement ceiling then going to the unit. The new duct has a couple of soft 90's due to clearing sewer and water line. Tech said the new design allows the air to flow more smoothly creating less turbulence.

I was amazed in the improvement. I still need to modify the return that is enclosed in the wall at least by adding another grill below it at floor level but right now it's 100x quieter. I didn't think the unit was workin right when we fired it back after the install because it was so quiet. But it's cooling as it was and same airflow from the vents.


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