Sound-Proofing a Dust-Collection Cyclone

Suggestions for keeping the dust-collection setup from being the noisiest thing in your shop. June 15, 2014

Question (WOODWEB Member) :
We recently installed a 5hp Oneida cyclone, and it's now the loudest machine in the shop. We threw a couple of packing blankets over it and reduced the sound to an acceptable level. We'd like to hang a shower curtain around the entire unit, but I have no idea what material to use that is readily available and decent looking. I'd prefer to avoid Sponge Bob sleeping bags. While likely very effective, I don't think they'd impress prospective clients when they tour the shop.

Forum Responses
(Dust Collection and Safety Equipment Forum)
From Curt Corum, forum technical advisor:
Try McMaster Carr catalog page 3495, Acoustical Insulation. They have sound absorbing pads (2" thick) that you can hang around the unit. They come with grommets on the edge. We used 2' x 4' panels for a similar situation. Pricing is not that bad.

From contributor M:
Isn't a 5hp typically below the CFM requirement to be installed outside?

From contributor J:
NFPA 664 states that if it is an enclosure-less collector under 5,000 CFM it can be located inside, but it can't be used in any automatic sanders. Anything else must be located outside with the appropriate venting or inside with the proper explosion suppression or with explosion vents, which must be ducted to the exterior. The vent duct must be the same and thick enough to withstand an explosion or deflagration. The vent duct must also not exceed the hydraulic duct diameter in length or it puts too much back pressure on the system.

From Gary Katz, forum technical advisor::
I built a flat wall enclosure around my cyclone and lined the inside of 1x4 walls with 1" rigid foam. The front panel removes with a single screw so it's easy to access the drum. I can run my dust collector without interrupting my concentration at all. It's more than a hum but not nearly as loud as my table saw or miter saw.

From contributor G:
Any holes larger than about 1/16 inch in an acoustic enclosure will become sound sources to the volume on the other side of the hole. There is a concept called a micro-perforated plate. About a few percent of the surface of the plate is taken up by holes. The holes are typically less than 1mm in diameter (0.3mm would be better than 0.8mm). The thickness of the plate should be about the same as the hole diameter. Doubling the thickness only increases sound absorption by about 1/3, so you don't gain a lot by going to thicker materials (mostly convenience in buying the plate). The plate can be made out of almost any material. The plate will tend to get warmer from the heat generated in the boundary layer air movement inside each hole, but unless one is looking at a lot of sound energy, this shouldn't be a big effect.

An older sound absorption technology than MPP, is mass loaded film. Typically the film is vinyl, and the mass is some kind of barium salt at one pound per square foot (two pounds per square foot is apparently available). It's flexible, and you could probably make curtains out of it. The sound term for this is the limp mass. Just theoretical knowledge to me (at the moment) as a project I am finishing is involved in sound and I am looking for information on curtain rods for something else (which is how I stumbled across this).