Noise control for dust collector?

[Jerome Sidley]

I hopefully will have my dust collector up and running shortly, it has been a struggle with many unforeseen issues. It is located on the first floor of my two story shop. with one wall separating it from the downstairs shop and I plan on building a couple more to fully enclose it leaving air passages for the return air to get back into the shop.
My question is what is a good material for the sound insulation that will not cost me an arm and a leg. Some of the ideas I have had are white styrofoam, moving blankets, Roxsol, fibreglass ceiling tiles. I'm sure there are more I've been told I'm at the end of the budget so the most inexpensive way is good it doesn't have to be pretty and it doesn't have to be dead quiet.

[Doug Dawson]

I hopefully will have my dust collector up and running shortly, it has been a struggle with many unforeseen issues. It is located on the first floor of my two story shop. with one wall separating it from the downstairs shop and I plan on building a couple more to fully enclose it leaving air passages for the return air to get back into the shop.
My question is what is a good material for the sound insulation that will not cost me an arm and a leg. Some of the ideas I have had are white styrofoam, moving blankets, Roxsol, fibreglass ceiling tiles. I'm sure there are more I've been told I'm at the end of the budget so the most inexpensive way is good it doesn't have to be pretty and it doesn't have to be dead quiet.

How loud IS your dust collector that it's in a separate room already, and it would still bother you? Do you work alongside monks? Methinks the chanting would be louder. :^) You can't throw the devil out the door and then let him back in through the window (the air passages will negate anything you could do with the walls, probably, unless you're using systems of baffles like they would use in a recording studio, etc.)

[Jim Becker]

I constructed my DC/Compressor closet with normal 2z4 studs. The inside is 1/4" hardboard pegboard with the rough side toward the noise. There's fiberglass (un-faced) insulation in the wall and the outside is clad with Homasote. This construction, combined with a baffled air return has been very effective for me in reducing noise considerably in the shop.

[Jerome Sidley]

Jim, I had to look up Homasote I've never heard of it. It seems it is not very common here in Canada.
What material did you use for the baffle system I have looked at all your posts but could not find it.
thanks

[Carl Beckett]

One of the best materials for sound deadening is mass loaded vinyl. Ideally this is not attached directly to the studs, but instead hangs freely (sometimes woven between two sets of studs that are offset from each other just to allow it to be woven in).

Personally, I have only used it in automobiles and not in a wall, but the home theater hobbiests have quite a bit of experience on how to deaden sound.

Other options might be acoustic ceiling panels. I have seen smaller rooms lined with egg cartons... lol.. not sure how effective that is.

Certainly filling interior walls with insulation is good. Isolating sheet rock from studs is another way to help (that is, do not attached the drywall to the stud directly - let it 'float') so that sound vibrations do not transfer directly through. Often this is overlooked - any direct transmission path will quickly become the weak link in isolation.

Finally - a big heavy blanket simply hung on the wall from the ceiling can have a big effect. I would think a dust collector is going to be relatively higher frequencies which are easier to dampen. Any loose foam or flexible material (usually have high acoustic impedance) will help.

[Allan Speers]

Certainly filling interior walls with insulation is good. .

Everything else Carl mentioned is spot-on. Really good ideas.

However, it should be noted that MOST of the time, if everything else is done right, you will get better transmission loss when the walls are empty inside.

I know this seems counter-intuitive, but I'm not making this up. I used to design & build recording studios for a living. It's in all the books. Dead air is a great isolator.

- but nothing else can touch, from ne side to the other.
FWIW, I used to prefer using resilient channel for wall construction.

[Jim Becker]

Allan, my DC/Compressor closet uses multiple materials which contribute to sound reduction, including the rough face of the back side of pegboard, fiberglass insulation, Homasote, drywall, etc. You are correct that different frequencies require different materials/techniques to capture and reduce the noise.

[Frank Pratt]

Everything else Carl mentioned is spot-on. Really good ideas.

However, it should be noted that MOST of the time, if everything else is done right, you will get better transmission loss when the walls are empty inside.

I know this seems counter-intuitive, but I'm not making this up. I used to design & build recording studios for a living. It's in all the books. Dead air is a great isolator.

- but nothing else can touch. FWIW, I used to prefer using resilient channel for wall construction.

Can you site some data for that? When I built my collector/compressor room I spent about as many hours researching sound reduction as I did building it & your statement goes counter to everything I read. Filling an empty stud cavity wall with insulation will result in a small improvement, but the same treatment in an isolated stud wall gives a very large improvement.

[Frank Pratt]

Just did a little quick search & both US Gypsum & Dow Corning have published extensive data for just about every stud wall assembly you can think of. For double stud construction with 2 layers of 5/8" board on each side & none between the studs, the difference between empty & insulated is about 10 - 12 STC higher for insulated.

[Allan Speers]

Just read any of the books about studio construction, includes those by the BBC. (They did massive research on the subject.)

Ot Alton Everest, who wrote the industry bible on the subject.

[Allan Speers]

Just did a little quick search & both US Gypsum & Dow Corning have published extensive data for just about every stud wall assembly you can think of. For double stud construction with 2 layers of 5/8" board on each side & none between the studs, the difference between empty & insulated is about 10 - 12 STC higher for insulated.

Either you're reading that wrong, or it's a very narrow frequency band.

[Frank Pratt]

Either you're reading that wrong, or it's a very narrow frequency band.

STC ratings are measured at 125 - 4000 Hz, which is not exactly a very narrow frequency band. Batt insulation is not as effective at absorption as frequencies drop below about 200Hz, but they do still contribute.

Edit, more info:

I did some reading in Alto Everest's 'The Master Handbook of Acoustics' & found the following that is relevant to this discussion.

From page 169:
"The transmission loss for porous materials is directly proportional tothe thickness traversed by the sound. This loss is about 1 dB (100 Hz)to 4 dB (3,000 Hz) per inch of thickness for a dense, porous material(rock wool, density 5 lb/cu ft) and less for lighter material."

From page 171:
"The last wall structure to be described is the double wall construction of Fig. 8-8. The two walls are entirely separate, each having itsown 2 × 4 plate.2 Without fiberglass this wall is only 1 dB better thanthe staggered stud wall of Fig. 8-7 but by filling the inner space withbuilding insulation, STC ratings up to 58 dB are possible."

From page 172:
"It was stated earlier that porous sound absorbing materials areof limited value in insulating against sound. This is true when normal transmission loss is considered, but in structures as those inFigs. 8-7 and 8-8, such porous materials have a new contribution tomake in absorbing sound energy in the cavity. This can improvethe transmission loss in some wall structures by as much as 15 dB,principally by reducing resonances in the space between the walls"

This book is a good read & there is much more, but I don't want to include too much here cause I don't know at which point I'll be bumping into copyright infringement.

While there is no disputing that stuffing a wall with fiberglass or mineral wool will aid with sound transmission, the economics of whether or not is used will vary case by case & that discussion is beyond me and there may be more efficient ways of obtaining the same level of sound attenuation.

[John K Jordan]

From page 171:
"The last wall structure to be described is the double wall construction of Fig. 8-8. The two walls are entirely separate, each having its own 2 × 4 plate.2 Without fiberglass this wall is only 1 dB better than the staggered stud wall of Fig. 8-7 but by filling the inner space with building insulation, STC ratings up to 58 dB are possible."

Great information! 58 dB "sounds" incredible. Can you push against the copyright a tiny bit more and tell what the book says about staggered stud walls when filled with fiberglass?

I used the staggered stud construction on a 2x6 plate with 2x4s stuffed with fiberglass and I thought the sound reduction was good. I can hear a whisper outside the closet when otherwise the sound level is painful. I probably get transmission through the ceiling/truss space too although also stuffed with fiberglass. My total wall thickness, with 1/2" ply panels on both sides, is 6.5". A double 2x4 wall would take up a lot more space for those with a small shop space.

I see the book on Amazon for about $40 (6th edition), a bit high for a casual read, but the Kindle version is a lot cheaper.

JKJ

[Jim Becker]

Jim, I had to look up Homasote I've never heard of it. It seems it is not very common here in Canada.
What material did you use for the baffle system I have looked at all your posts but could not find it.
thanks

Homasote (a brand name) is basically a "low density fiber board" and I suspect you can find something similar in your geography. It's kinda like ceiling tiles but not as brittle.

For the baffle, I actually used a joist bay as the cross sectional area was large enough when split in two on a horizontal plane to support more than the air movement required for return air. Material doesn't matter, but I did happen to use some pieces of left-over Homasote for the two pieces needed to divide the space and put a bottom on it. Here is an illustration that I've posted a number of times that shows how things are constructed in my particular case.



Some folks, like John Jordan, used large diameter flexible duct, like would be used for air returns in a home HVAC system, for the air return to the shop. What you use to make it is less important than making it large enough to have free air flow and insuring it's not a direct path for sound transmission. (turns/bends required)

[Bernie Kopfer]

I constructed my DC/Compressor closet with normal 2z4 studs. The inside is 1/4" hardboard pegboard with the rough side toward the noise. There's fiberglass (un-faced) insulation in the wall and the outside is clad with Homasote. This construction, combined with a baffled air return has been very effective for me in reducing noise considerably in the shop.

That is pretty much what I did and the measurements showed over a 10db drop. What was amazing was how important it was to seal the closet literally air tight, except for inlet and outlet, to achieve noise reduction.