Author Topic: Brownstone - Roof compressors make low pitched noise  (Read 3496 times)

rosskevin

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Brownstone - Roof compressors make low pitched noise
« on: August 22, 2011, 02:32:49 AM »
Hello all,

In our new construction brownstone, there are two compressor units on the roof.  They make a low pitched "wahwahwah" noise on the top floor and I'm wondering what the best approach is to tackle the problem.

There appear to be anti-vibration feet on the units, and the units themselves don't appear to be wobbly.  The roof decking is OSB wood, and the rafters are wooden.  The roof is mainly asphalt shingles with the part of the roof with compressors (barely sloped) being some kind of rolled roofing.  I have just taken possession, so I have not checked to see if there is any vibration between the roof decking and rafters.

I'm one that would error on the side of overdoing it, instead of underdoing it.

What is the progression of items (in order of effectiveness) that I should do to try and tackle the problem?

Randy S

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Re: Brownstone - Roof compressors make low pitched noise
« Reply #1 on: August 22, 2011, 03:54:11 PM »
Decouple the unit as best as possible from the structure using vibration pads and decouple any straps and pipe clamps by putting foam mat between the pipe and the clamp/ strap and unit.

http://shop3.mailordercentral.com/supersoundproofing/prodinfo.asp?number=09-42720

Then you can put Mass loaded vinyl 2lb. under the unit with a footprint 2' or larger all the way around.

http://shop3.mailordercentral.com/supersoundproofing/prodinfo.asp?number=09-00005-45-2


Randy Sieg

Super Soundproofing Co
www.soundproofing.org
888-942-7723
Ph. 760-752-3030
Fax.760-752-3040

rosskevin

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Re: Brownstone - Roof compressors make low pitched noise
« Reply #2 on: September 04, 2011, 04:01:08 PM »
Thank you Randy, I'll measure out the units and order the MLV, also I will assess any hard connections.

I have an SPL meter, should I have a measurable difference before and after at these frequencies with this simple Radio Shack meter?

I have more to add since we put a dehumidifier in the attic space.

I have now moved into the home, and while the upstairs has the "wahwahwah" sound, there is a low frequency noise prominently in the room with the attic door, as well as down into the 2nd floor .  It is a 3 floor home, with 2 compressors on the rooftop, one hvac in the attic, and one dehumidifier in the attic.


rosskevin

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Re: Brownstone - Roof compressors make low pitched noise
« Reply #3 on: September 04, 2011, 04:06:27 PM »
(second part of my reply, first rejected because it was over 1000 characters, second rejected because the first part was posted less than 120 seconds ago, the third because I already submitted this post?  ??? )

After doing some more reading, here is my plan, please correct me where there is something better:
1.  Add isolation pads to all feet of the 2 compressors and 1 dehumidifier
2.  Add the MLV above to the 2 compressors and the 1 dehumidifier
3.  Redo any pipe bindings with foam to isolate
4.  ? Use an extra piece of MLV to roll over the attic door to isolate the living space?

Thank you

Randy S

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Re: Brownstone - Roof compressors make low pitched noise
« Reply #4 on: September 06, 2011, 04:24:50 PM »
Yeah the forum has some very unique rules.. :)

Ok, I want to make sure you achieve the reductions you are looking for.

I would be best if you give me a call on our toll free number
888-942-7723

So you and I can discuss every aspect that might play huge roles in the reduction of sound.

with 1000 character limits it might take a long while haha
Randy Sieg

Super Soundproofing Co
www.soundproofing.org
888-942-7723
Ph. 760-752-3030
Fax.760-752-3040

rosskevin

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Re: Brownstone - Roof compressors make low pitched noise
« Reply #5 on: May 03, 2012, 02:46:08 PM »
I'm just getting around to doing this and several other soundproofing projects.  I just wanted enter a quick post to encourage others to talk with Randy about their situation.  I received quite an education in just a few minutes with him, and a few tests confirmed the path for me to take.

Thank you again for your time, and everyone else...call him!