Fine Woodworking Shop Vac Muffler

[Backhertz]

http://www.taunton.com/finewoodworking/Workshop/WorkshopArticle.aspx?id=29740

This is a video on building a 25 dB muffler for a shop vac. Here is the article:

"Veneer specialist Thomas R. Schrunk has found an easy solution to the noise generated by a shop vac. He constructed a box from 3/4-in. particleboard, lined it with acoustic padding, parked the vacuum inside, and shut the door. In this exclusive video, you can hear how much of a difference that makes.
Schrunk's box is as effective as many hearing protectors, producing a 25-decibel reduction in sound. That takes the vacuum down from a loud scream to a level below that of average conversation."

 

[Guitarman]

Shop Vac noise reduction

Shop Vac noise reduction

I did a similar setup with MDF and lined it with carpet and had the same results. It is my intention to build a muffler which will enclose the impeller housing and the filters with the same materials for my dust collector. More to come. Regards, Guitarman.

 

[Bill]

Noise Control

Noise Control

When you make sound reduction enclosures, you have to make sure that the motors have proper cooling. In the case of a flow thru vac motor, it is pretty simple because the air through the hose goes through the motor to cool it. You have to be careful not to dead end the hose too long though on a flow thru motor. If you have a vacuum bypass motor, or an induction motor like the Leeson, you have to provide a cooling path in and out of the enclosure for the separate motor cooling air or else keep cool air moving through the enclosure by another means (separate fan, etc).

The principle behind enclosures lined with acoustic material is to absorb the sound energy. As the sound bounces around inside, bouncing off the lined hard surfaces, it passes back and forth through the acoustic material and the sound energy is dissipated in the form of heat (a minute amount of heat). As long as the path for the air in and out of the enclosure is designed such that the sound has to bounce off absorbing surfaces on its way, the noise will be reduced. You don't want any direct (straight) paths out of the box unless they are long (relative to the area or diameter) and lined with acoustic material. It is usually best to have a lined "torturous path" in and out of the enclosure to give the sound waves more opportunity to bounce off surfaces. Viscoelastic acoustic foam is one of the best, but other materials will work pretty well too. You can use fiberglass, open cell foam, cheap fiberglass ceiling tile with the surface removed, etc. Anything that the sound can pass through and lose energy.
Open cell carpet foam might work well too if it isn't too dense. Often carpet stores will have scraps of brand new foam in their dumpsters. I dove for some once and plan to do it again. One more thing to think about is fire. If you have flamable surfaces inside a ventilated box and you start a fire, you have a tinder box. I think I would address this concern with a smoke detector near the enclosure vent, since it would only be on when I was there.

 

[Guitarman]

Noise control

Noise control

I thank you for your reply, you have given me several points to think about. My noise control system for the the dust collector was in the rough drawing stage. Your information has helped to finalize it. Thanks.
My piping is finished and the T/S is plumbed into the system now I have to get the DC finished. Pictures will be posted soon. Regards, Guitarman.

 

[Bill]

Muffler

Muffler

I noticed that some people are using 8" flexible insulated duct for a muffler between the blower and filters. I would like to know how this is working. I would think that it would need a hard shell on the outside to work well. I am thinking about using the 8" insulated duct with a sheet metal shell. Is the restriction of the 8" flexible duct a concern (6' long)? If you muffle the blower output, is there still a lot of noise from the cyclone and blower housing?

 

[DuaneD]

I just finished an installation in which the cyclone is outside the shop and the return to the filters (inside the shop) has about a 10' run of 8" insulated flexi-duct. You DO NOT need a sheet metal shell.

Outside the shop you need to yell to talk to someone. Inside you don't need to raise your voice.

Duane