Noise control for dust collector?

[Peter Christensen]

Larry you can talk but can you be heard? What will drive one person nuts won't bother the next.

[Larry Frank]

I can talk and be heard without yelling. It doesn't bother anyone in the house.

[Allan Speers]

Lots of good info on this thread, but one thing that rarely gets discussed (and I don't have the answer, as I have yet to install my cyclone) is: in WHAT FREQUENCY RANGE is the loudest noise?

While isolation is the key, part of the sound "proofing" solution is often to absorb some of the noise at the source. (turning it into mechanical energy) Someone above mentioned sound board (homeosote.) That's pretty good stuff, but for a very limited frequency range. So is MDF. So is Mineral wool, which comes in different densities. (lbs per cubic foot)

You need to know what frequencies you're targeting, if you want to maximize your efforts. Then you can look up materials in the STC charts & such.

Perhaps someone here knows the typical numbers?

[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

[Ole Anderson]

I left the inside of my DC closet bare studs with Roxull Safe and Sound mineral wool insulation batts between studs. I constructed the door of 1/2" OSB sandwiching 1/2" sheet rock. Air returns above the door through the joist cavity with the Roxull on the joist to catch reflective sound. One wall of the closet is a poured concrete basement wall. Here is a video of the SPL difference, door open and closed: https://www.youtube.com/watch?v=8X8qwMqm3Ek (amazed that this simple YouTube video has gotten over 13,000 views).

[Frank Pratt]

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

John, a pdf of the book is available here for free download
http://the-eye.eu/public/WorldTracke...01%29%20WW.pdf

It goes deep into the technical theory & details of sound, but there is a chapter that covers wall assemblies. For more easily digestible data, there are several websites that publish tables showing various wall assemblies & their STC ratings. Just do a search for "STC ratings for wall assemblies".

My walls have around STC of 65. With the door closed, standing 3' away, the collector cannot be heard at all. I built a true 'room within a room' with 2x 5/8 fire rated drywall & Greenglue on each side & 6" of Roxul Safe-n-Sound insulation. Total wall thickness is 8.5" using 2.5" steel studs.

[John K Jordan]

John, a pdf of the book is available here for free download
http://the-eye.eu/public/WorldTracke...01%29%20WW.pdf

THANKS! I got it - an amazingly quick download too for a 600 page book. (Amazon warned that the Kindle download would take a long time.)
The illustrations are great.

JKJ