How do I sound proof furnace intake vent?

[Dunderbeck]

Hi,
I asked in another post about picking a receiver and sub woofer, but I have a big problem in trying to set up my home theater. In the room my home theater will be in there is the intake vent to the furnace. It goes off and on intermittently, and it is LOUD! I have to turn the TV up and then when the heat stops turn it down. I need to Soundproof it somehow while not covering it up (it must take in air). Getting a more open grill won't work the noise is from the intake fan.

So far the only ideas I have or have gotten are:

A. Put a divider of some kind, possibly two tall bookcases, or cubical walls, or something similar around it in an L shape so it can take in air, but will be obstructed from my hearing, and then sound proof the dividers, whatever they may be. If someone has an idea for a good divider please suggest it, it has to be taller than the vent, but not as tall as the ceiling (10'). The TOP of the vent is 50" off the ground (4' 2").

B. The other idea is to get a duct that fits over the vent. The Duct piece over the vent would turn upwards, and the rest of the duct would go straight up the wall for a few feet, allowing the vent to suck air from a new direction. After attaching the duct to the vent and the wall I would cover it in sound proofing.

I rent so I can't get a quieter fan motor unless the landlord agrees, but I'll ask. Assuming he won't put in a new motor please give me suggestions on other things I can do, or ways to achieve or improve upon the above two ideas.
Thanks

 

[joshus77]

I think you are in a bind. You don't want to completely cover your home ventilation but I understand the sound concern.

You can build a sound proof wall as a duct extension and use acoustic pads, insulation, and sound proof drywall to line it. May help but probably not worth the time and money; it will not completely eliminate the sound.

The unethical way would be to sabotage the unit and have the landlord put in a new one. At that time, you mention how the last one was loud and request a quieter one cause it would wake you up at night when it went off. Renter bonus.

Good luck!

 

[avnetguy]

Redirecting the intake without blocking it might help some, also changing the ducting (if accessible) leading to the vent (putting small right angles in) might help to reduce the sound. If this is a newer furnace, high efficiency type with a variable speed fan motor, many have dip switches to change the fan motor speed and for your case, lower it. Normally these are set when the furnace is setup based on the ducting and sq ft area of the home but all too often are just left on default and are incorrect.

Steve

 

[Dunderbeck]

the switch?

First it doesn't have to be completely sound proofed. I'd be fine with a hum that wasn't avoidable, but not so loud I couldn't hear the TV.

This Switch interests me. Where would it be in the furnace closet near or far from the on off switch, or near or far from the fan? How many settings, and what should I set it to? Please give me more info about this, maybe even a link to a site with a diagram.

If I thought I could get away with it I would break it, and try to get a quiet one.

 

[spyder152]

Using duct board to line the compartment will help, but the cheapest fix is turn it off when you watch tv, and adjusting the switches wouldnt help unless you had a manual for the furnace, assuming it's a newer unit. If it is turning on and off with the tstat off, then there is a problem with the unit, get it fixed or unplug it

 

[avnetguy]

This Switch interests me. Where would it be in the furnace closet near or far from the on off switch, or near or far from the fan? How many settings, and what should I set it to? Please give me more info about this, maybe even a link to a site with a diagram.

The only way to know is to get the owners or service manual for the furnace.

Steve

 

[Nestor]

Hi,
I asked in another post about picking a receiver and sub woofer, but I have a big problem in trying to set up my home theater. In the room my home theater will be in there is the intake vent to the furnace. It goes off and on intermittently, and it is LOUD! I have to turn the TV up and then when the heat stops turn it down. I need to Soundproof it somehow while not covering it up (it must take in air). Getting a more open grill won't work the noise is from the intake fan.

So far the only ideas I have or have gotten are:

A. Put a divider of some kind, possibly two tall bookcases, or cubical walls, or something similar around it in an L shape so it can take in air, but will be obstructed from my hearing, and then sound proof the dividers, whatever they may be. If someone has an idea for a good divider please suggest it, it has to be taller than the vent, but not as tall as the ceiling (10'). The TOP of the vent is 50" off the ground (4' 2").

B. The other idea is to get a duct that fits over the vent. The Duct piece over the vent would turn upwards, and the rest of the duct would go straight up the wall for a few feet, allowing the vent to suck air from a new direction. After attaching the duct to the vent and the wall I would cover it in sound proofing.

I rent so I can't get a quieter fan motor unless the landlord agrees, but I'll ask. Assuming he won't put in a new motor please give me suggestions on other things I can do, or ways to achieve or improve upon the above two ideas.
Thanks

I'm guessing the return is a direct and short path to the furnace blower.

Three things I can think of:

1. Re-do the return with sound absorbing liner.
2. Add a 90 degree if it's a direct path. Re-locating the duct may help.
3. If air velocity is part of the noise, make the return larger.

I'm no HVAC or acoustics guru, so take these with a grain of kosher-sized salt.

 

[TLS Guy]

A lot of modern HVACs have very noisy fans. We were in a rental in Grand Forks, for a year, and that furnace made a truly massive amount of noise.

It won't help to destroy the fan motor as, it will be replaced by one of the same type, as it has to fit.

A lot of older furnaces had belt driven longer roller roller fans, with a slow rotation speed. In these money grubbing times I have not seen a fan like that for years. They are small direct drive squirrel cage fans now and unless they can be slowed make a fierce noise.

Basically it makes basements useless for audio and home HT these days.

Unless that fan can be slowed you are basically stuck, and you will have to turn your HVAC off when doing your listening.

 

[Alex2507]

Similar topic to read over:

http://forums.audioholics.com/forums/room-acoustics-system-layout-setup/33543-guess-frequency.html

 

[slipperybidness]

How old is the fan on the furnace? You may find that just a good servicing of the unit would help quite a bit. Maybe, or maybe not, but might be worth investigating.

 

[mtrycrafts]

....

I rent so I can't get a quieter fan motor unless the landlord agrees, but I'll ask. Assuming he won't put in a new motor please give me suggestions on other things I can do, or ways to achieve or improve upon the above two ideas.
Thanks

I am with TLS. Not much you can do in an apartment, no matter what and you would not get away with damaging the unit. Any modification would be on the outside of the wall as I am sure the landlord will not let you modify the apartment, even at your cost.
Put on a sweater and turn it off while watching

 

[Rubicon_Joey]

Don't have any real solutions but, as a renter I also feel your pain. My intake is also quite loud as well (not loud enough to bother me like yours though). My refrigerator on the other hand sounds like a 747 taking off in my kitchen when it runs. When I first moved in it would wake me up at night and sometimes still does.

You might try opening the return cover (ie less constriction) when watching a movie or just turn it off. May also try hanging a thick quilt to isolate the noise and act as sound dampening. If it's truly loud you might be able to claim it causes hearing loss.

 

[Dunderbeck]

I'm guessing the return is a direct and short path to the furnace blower.

Three things I can think of:

1. Re-do the return with sound absorbing liner.
2. Add a 90 degree if it's a direct path. Re-locating the duct may help.
3. If air velocity is part of the noise, make the return larger.

I'm no HVAC or acoustics guru, so take these with a grain of kosher-sized salt.

What is a sound absorbing liner? Is there a link? Would it go over the openning, and still let in air?

The bulk of the noise is the intake fan. The furnace is right behind the wall, and it turns on and off to stay at a certain set temprature I choose on the thermostat. The furnace makes a bit of noise, but when you open the intake grating over the fan, you see the fan is the problem it is very loud. I think the motor. I was talking about maybe putting a duct over the opening that redirects the air intake, Possibly the 90 degrees mentioned" and putting sound proofing around it, or putting a bookcase or other divider between it and me at an angle or 2 dividers in an L shape, so it can still take in air, and the sound will be minimized.

Do you think replacing the motor would help, or even lubricating part of it?

 

[TLS Guy]

What is a sound absorbing liner? Is there a link? Would it go over the openning, and still let in air?

The bulk of the noise is the intake fan. The furnace is right behind the wall, and it turns on and off to stay at a certain set temprature I choose on the thermostat. The furnace makes a bit of noise, but when you open the intake grating over the fan, you see the fan is the problem it is very loud. I think the motor. I was talking about maybe putting a duct over the opening that redirects the air intake, Possibly the 90 degrees mentioned" and putting sound proofing around it, or putting a bookcase or other divider between it and me at an angle or 2 dividers in an L shape, so it can still take in air, and the sound will be minimized.

Do you think replacing the motor would help, or even lubricating part of it?

It will only help to change the motor if there is the sound of metal against metal, i.e, a bad bearing.

The problem with a lot of these modern furnaces is a small squirrel cage that rotates too fast causing a lot of air turbulence.

I don't know a cure for that except a new furnace of different design.

 

[Alex2507]

Duct liner would go on the enclosure walls surrounding the fan. I talked about that in the link I provided but you can get it at an A/C supplier. It would reduce echo/ringing/reflected sound from reaching your room. I take it you don't have a return air duct but just a return air grill so lining the duct is out of the question for you but for people who do have that it's the biggest bang for the buck solution.

My fan motor had an oil hole on the shaft or axle. The motor had to be removed to access it. YMMV. Cleaning off the accumulated gunk on the squirrel cage would also cause less turbulence making it quieter. It's a matter of knocking out a db here and a db there. It adds up and for me the final result was a huge improvement.

To redirect the air I closed off the front and side of this little table with 2 layers of sound proof carpeting and applied weather stripping at the top where it meets the wall and hutch (black line). Normally I have it away from the wall but when I watch movies I can slide it up tight like it is in the pic and the noise level of the fan drops 3db at my listening position.

 

[Dunderbeck]

Nice Photo Alex

Hi,
First of all TLS you're right, I looked, it's not the motor its the turbine fan noise.

Second of all Alex this is genius. I think I'm gonna try this. Mine will have to be taller because my intake is 4' 2" off the ground (that's the top of the vent the bottom is 17 and 1/2" lower). I'll also have to put another peice of sound proofing carpet or something at the bottom of the vent, and maybe will have to fill the space between the bottom and the floor with foam or something, assuming it's a table like thing i use.

Do you think I have to fill the space between the bottom and the floor with foam or something, or is one layer of soundproof carpet, or other soundproofing enough?

What type of sound proof carpet did you get, and where can I get it cheap? What other material did you use?

What do you think I can use instead of a table since the vent is so high? All I can think of is putting a small table on another tall piece of furniture like a dresser or something. What do you think. Mine is like yours, but as high off the ground as I said. I'd put in a photo, but am unsure how to get one off my phone, and on this site. Just in general how do you think I should redo your idea for a higher vent?

Can you please draw a diagram of your creation, and put the scan or photo on this thread? If you have ideas how I can do the same thing 3-4 feet off the ground you can do a diagram of that too.

This really is what I've been looking for; you should patent this thing. Please let me know about the specific carpeting you used and where to get it cheap.

Thanks

 

[Alex2507]

Hi,
First of all TLS you're right, I looked, it's not the motor its the turbine fan noise.

Is the turbine clean?

Second of all Alex this is genius. I think I'm gonna try this. Mine will have to be taller because my intake is 4' 2" off the ground (that's the top of the vent the bottom is 17 and 1/2" lower). I'll also have to put another peice of sound proofing carpet or something at the bottom of the vent, and maybe will have to fill the space between the bottom and the floor with foam or something, assuming it's a table like thing i use.

All you have to do is make the air take a 90 degree turn to muffle the direct noise of the fan.

Do you think I have to fill the space between the bottom and the floor with foam or something, or is one layer of soundproof carpet, or other soundproofing enough?

You could hang a box with one side open on a French cleat. Just make sure your open side has the same surface area as the return grill so you don't create a bottle neck.

What type of sound proof carpet did you get, and where can I get it cheap? What other material did you use?

It's just carpet squares with a decent padding that I got from work on construction. Check Home Depot or a carpet supplier for remnants. Plywood with duct liner would be best. I just used what I had.

What do you think I can use instead of a table since the vent is so high? All I can think of is putting a small table on another tall piece of furniture like a dresser or something. What do you think. Mine is like yours, but as high off the ground as I said. I'd put in a photo, but am unsure how to get one off my phone, and on this site. Just in general how do you think I should redo your idea for a higher vent?

Like I said, hang it off the wall. It's just a box that makes the air turn so you don't have a straight shot to the fan.

Can you please draw a diagram of your creation, and put the scan or photo on this thread? If you have ideas how I can do the same thing 3-4 feet off the ground you can do a diagram of that too.

You can Google French cleat. I can't do diagrams but I'll post better pic's in a day or two. Use Photobucket for pic's and set your resolution to 800x600 so they don't blow up the page when you post them.

This really is what I've been looking for; you should patent this thing. Please let me know about the specific carpeting you used and where to get it cheap.

The carpet is just what I had kicking around and I'm unsure of the type. Ask a supplier about that stuff. They'll know but duct liner in a plywood box would work better. Read over that other thread. I remember MDS saying he had decent results.

 

[Rickster71]

This is interesting and may offer some insight:



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[Alex2507]

Here's a better look at the table. This is the side that goes up against the grill.

I now see that I added a layer of that carpet to the underside of the lid too.

I used those little wood cleats to attach the corners and to secure the side carpet to the lid.

You can see the screws that go into the cleats. There is a curved notch in the carpet to allow for the base around the hutch.

I really need to take a fuzzy wuzzy vacuum attachment to that table and grill but you can see how it all snugs up. If I have it pulled even a 1/2" away from the wall it's effectiveness is reduced to zero.

All that stuff is just scrap from work. The table was 3 bucks at a flea market but I refinished it so it doesn't look like what it is: somebody else's garbage. The table and floor just make up a box with one side open ... a duct if you will. You just need to figure out what side you want open. Having the bottom open in your case might work best as dust wouldn't settle in it and you could use the top as a shelf.

 

[Nestor]

What is a sound absorbing liner? Is there a link? Would it go over the openning, and still let in air?

The bulk of the noise is the intake fan. The furnace is right behind the wall, and it turns on and off to stay at a certain set temprature I choose on the thermostat. The furnace makes a bit of noise, but when you open the intake grating over the fan, you see the fan is the problem it is very loud. I think the motor. I was talking about maybe putting a duct over the opening that redirects the air intake, Possibly the 90 degrees mentioned" and putting sound proofing around it, or putting a bookcase or other divider between it and me at an angle or 2 dividers in an L shape, so it can still take in air, and the sound will be minimized.

Do you think replacing the motor would help, or even lubricating part of it?

No, the liner is part of the duct. If you're renting, I'm not sure how much duct mods you would be willing (or allowed by your landlord) to do.