# Noisy duct register



## Tinstaafl (Jan 6, 2008)

I'm working up a proposal to build a home theater room in a basement/garage area. The main trunk for the furnace/AC is immediately adjacent to the space (I'll be enclosing that in a bulkhead), and currently has a register in it that the HO says howls like a banshee when open.

That register location will be ported into the home theater room, and of course any noise from it would be objectionable. Would just reducing the "port" size quiet it down significantly? What are my options?


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## Inner10 (Mar 12, 2009)

Reduction in size would increase the velocity and increase the noise no?

I had some noisy ventilation in one of my installations and an HVAC guy took pliers and bent the fins of the grill to allow increased air flow to reduce the noise.


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## Tinstaafl (Jan 6, 2008)

Inner10 said:


> Reduction in size would increase the velocity and increase the noise no?


It would if you were talking about narrowing the main duct, but this is just a hole in the side of that duct--about 15' from the rather sizable blower. I'm thinking that the noise is more likely due to the quantity of air rather than its speed. Smaller hole = less total air flow.

Maybe so, maybe no?


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## donerightwyo (Oct 10, 2011)

An old HVAC guy we had, whenever he was worried about noise like that he would add a 10+ ft length of insulated flex before the supply boot. It seemed to work pretty well. Sometimes it looked kind of funny having all that extra hose to nowhere:laughing:


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## Inner10 (Mar 12, 2009)

Tinstaafl said:


> It would if you were talking about narrowing the main duct, but this is just a hole in the side of that duct--about 15' from the rather sizable blower. I'm thinking that the noise is more likely due to the quantity of air rather than its speed. Smaller hole = less total air flow.
> 
> Maybe so, maybe no?


I really don't know...I have an HVAC guy I leave that too. But for home theaters we make the supply and air return ducts S curve to reduce noise transmission to other parts of the house.


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## Tom M (Jan 3, 2007)

Im thinking that since its so close to the source nothing will matter. Hopefully there is a canvas boot transition to absorb start up noise. But an in line diffuser/damper may be a way to limit the volume of air traveling by and bring a better flow to your new area.


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## griz (Nov 26, 2009)

Tinstaafl said:


> I'm working up a proposal to build a home theater room in a basement/garage area. The main trunk for the furnace/AC is immediately adjacent to the space (I'll be enclosing that in a bulkhead), and currently has a register in it that the HO says howls like a banshee when open.
> 
> That register location will be ported into the home theater room, and of course any noise from it would be objectionable. Would just reducing the "port" size quiet it down significantly? What are my options?


I recently had this problem with a radio station.
Donerightwyo got it...:thumbup:

In my case it took two lengths of flex to quiet the beast down to an acceptable level...:thumbsup:

PS: Put the flex in a loop....


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## Tinstaafl (Jan 6, 2008)

Believe it or not, I did have a hazy notion of flex duct percolating among the cobwebs. 

In order to do that, I'd have to enlarge the bulkhead around the trunk, intruding on the planned coffered ceiling space and throwing its geometry a bit out of whack. Hmm...


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## beenthere (Mar 5, 2009)

Making the opening smaller will generally increase the noise. Plus, a theater room needs a lot of air flow.


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## Caslon (Dec 15, 2007)

I had the same noise problem in my intake cavity. Two things I did cut the noise in half. I used some well outgassed carpeting and lined the cavity, stuck on with non-toxic glue and staples. Its easy to remove to replace, just cut the same size squares of carpet. I used a USPS shipping box, size 14" x 12" x 3 1/2" and wedged it up near the front of the 2x4 framing of the intake, directly under the furnace. The cavity was big enough that airflow was directed around the cardboard shipping box wedged into place, cutting down the sound considerably.

The cardboard box blocked furnace noise previously heard at my intake grill, while allowing ample air to go around and up.


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## rselectric1 (Sep 20, 2009)

Have you checked for banshees in the duct?

Sorry, I couldn't resist...bad day. Carry on!


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## Tinstaafl (Jan 6, 2008)

I can see how both would help, but I don't think I'd want the dust-catching carpet in there (for a client, anyway). Good idea with the baffle. :thumbsup:


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## Tinstaafl (Jan 6, 2008)

rselectric1 said:


> Have you checked for banshees in the duct?


I've never met one and don't want to.


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## beenthere (Mar 5, 2009)

Whats wrong with this banshee.


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## Tinstaafl (Jan 6, 2008)

I 'spect she'd throw me before the requisite 10 seconds. :laughing:


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## griz (Nov 26, 2009)

Tinstaafl said:


> I 'spect she'd throw me before the requisite 10 seconds. :laughing:


:laughing::laughing::wheelchair::wheelchair:


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## beenthere (Mar 5, 2009)

Tinstaafl said:


> I 'spect she'd throw me before the requisite 10 seconds. :laughing:


 I'd brake my neck on it.


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## adamv. (May 10, 2013)

Hi,

We recently did some ventilation works in a house, and as mentioned previously, the air silencers work really well, the longer the length, the greater the silencing effect, along with soundproof flexi ducting.

HTH


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## sleepybear (Apr 6, 2013)

With the new unit, it should not be noisy at all.


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## BCORP (Jun 27, 2013)

Use a 7'' take off on the side of the supply duct with the air flow facing in the direction of the furnace. Run insulation flex duct to the register.
Problem Solved!


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## Rich D. (Oct 14, 2011)

Get a duct made with duct liner installed in it..

http://www.certainteed.com/products/insulation/mechanical-industrial/317383

On a previous job i had the hvac guys line a trunk line that went through a sound proof room. It deffinitly did its job.


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