Need to reduce noise between rooms that share vent

We have two rooms in our house that we use as offices. The two rooms share a HVAC return vent. It's a common return duct that has a cover in each room that are back to back. You can look through the louvers and see into the other room.

Voices travel so freely through the vents between the rooms that phone conversations in a normal tone of voice are distracting. I'm looking for a way to dampen the noise and still allow the return to function. I tried a piece of board between the vents which still allowed air to enter from either side but it wasn't effective.

I was hoping there was a professional or manufactured solution.

Hi RobH2, welcome to the forum

I have unfortunately no idea about this one. I simply never heard of this problem before. Usually if phoneconversations are unreasonably loud it depends on the acoustics of the rooms. Have you considered lining the ducts with foam or other absorbing material?

Rob,

Hoping you got the standard 3.5"+ clearance in there ??

Try stapling a sheet of Foam to one/both sides of that board.

Maybe that Egg Crate Material might work also, it's a little thicker though.

Dense/Fine Filters in both sides of the Return Air Box/Frames.

One or more of the above !!

Have a good Day !
S.W.

Thanks for your suggestions.

If there wasn't a manufactured/professional solution I was thinking about getting one or two of the acoustic panels that are used in sound recording studios and hanging that in the center of the wall and down the duct about a foot. That way air could return from either room, travel down on both sides of the acoustic panel and meet 12" down to continue back to the furnace. No question about their sound absorption abilities. They are expensive to do an entire room but one or two won't be much.

Both rooms are furnished with enough soft stuff that they aren't causing the problem. My walls are plaster and are very soundproof. I think the problem is that the returns are at the height of the ceiling on the walls and the sounds fly through unchallenged by furniture, carpet or any other normal buffer when they are installed near the floor.

Thanks,

RH

RobH,

Sounds like a good fix to me !

I had second thoughts about the Egg Crate, choking down the return CFM.
Hopefully that SP Material is thin, one 3.5x16 space sounds a little weak for two rooms, at best. Good Luck !

Have a good Day !
S.W.

Post edited by: SWHouston, at: 2008/08/06 22:49

Both returns and supplies of HVAC are supposed to terminate at the heater/cooler. They shouldn't be shared between rooms for just this reason.

This may also be against some fire codes as there is no separation if a fire were to break out in one of those rooms.

Post edited by: jmborchers, at: 2008/08/10 16:37

Understood but whether right or wrong it was the way the house and about 800 others like it in our neighborhood were built 60 years ago. I'm not inclined to tear out walls. All I want to do is reduce noise.

jmborchers,

You're perfectly right ! That's why (in the US anyway) the Fire/Building Codes have changed, prohibiting the use of "Plenum Return", which basically is what Rob has, even if it's just two rooms.

I know in the many years of Building Maintenance, I've trashed numerous Work Orders, because of Noise, Odors and sometimes even unwanted Light which is caused by this apparent oversight in older Codes.

There must be thousands, even millions of Structures which still have this approach to Return Air still existing in my area anyway. I suppose the only good part about it, was that the Maintenance guys only had one place to change the Filters out at.

Rob,
No doubt you got a tough problem there, and may not be able to satisfy it completly. But as least it's just you dealing with it, think of how I felt, when I had a Tennant who was paying $1500.us a month in my face, and I couldn't do anything about it !

Have a good Day !
S.W.

One thing you could do is put something over the vent to provent direct sound waves from going straight through like a hood. The bad part about this is it would project about six inches into the room.

The other thing you could do is hang a flap of vinyl rubber in the space in between. you want something that's 94V-0 for fire rating.

See Mcmaster Carr - www.mcmaster.com

Look up - "Vinyl Acoustical Barriers"

The Vinyl Acoustical Barrier looks like a good approach. It should surely help. It may not be as good as a wall but it surely can't hurt.

Thanks for all your comments.