Quieting DC exhaust

[zayd alle]

Hello, folks.

I just set up a 3hp cyclone in my garage shop and have run the 7" exhaust outside. My plan was to test the sound and make a determination if I needed to exhaust indoors via filters. Right now, running the pipe straight outdoors creates a little more sound for the neighbors than I'm comfortable with, given their relatively close proximity.

My question is simple: are there in-line silencers or point-of-exit baffles that can reduce the sound output? Anything else you folks have found success with?

FYI, the ducting currently leaves the blower and makes a couple 45-degree turns into a 5-foot straight shot outside.

Thanks.

Zayd

[Dan Hintz]

Blow it into a big box with cheap filters around it... that will cut down on some noise. How much do you want to spend, and how much time do you want to spend building it?

[John Lanciani]

I'm no fan of Bill Pentz, but the muffler plans he has (or used to have anyways) on his website are actually quite effective and pretty cheap and simple, too. If you have 5' of straight pipe now,you have plenty of room to put one in the exhaust duct. You can also buy one ready made from Oneida if their price doesn't give you a heart attack.

[Lee Schierer]

Put a sweep 90 on the end of the duct pointing up clear of the roof or any other obstruction you'll be amazed at the noise reduction. You will need to drill a small hole in the bottom of the duct to let the rain out.

[David Giles]

+1 on installing a 90 degree turn. Simple, cheap, fast. And keep some spare ear plugs handy for your neighbors in case they complain.

[Rod Sheridan]

The turn up elbow is a good suggestion, in addition cut the open end of the pipe at a 45 degree angle also, facing away from the house............Rod.

[Doug Palmer]

Use a Dynamat type product. It is for sound deadening in automobile trunk and cabin areas. Use the cheaper alternative you can get at Lowes called Peel & Seal. It will say it is for Aluminum Roof Repair. This is the stuff $15 and you will be amazed at the difference. It stops the reverberation of the duct caused by the turbulance of the air flow. You could use the real Dynamat product (look it up on the internet), but may have to fork out a couple hundred bucks. JMO

[Bob Riefer]

Hey Rod - what is the 45 degree cut for? Just curious

[zayd alle]

Good suggestions -- thanks.

To be sure I understand the majority opinion -- a simple turn upwards in the exhaust once I get outside will direct the flow (and resulting noise) upwards and reduce the perceived sound by the neighbors? I can see that.

Now can I use galvanized pipe for that? I anticipate it will eventually succumb to rust, but I'm guessing it should last long enough until I can fashion something out of alumimum flashing or something. As Lee mentioned, I can drill a drain hole for water to escape. And I'm guessing a large wire mesh should keep the birds and rodents out.

As for a muffler -- thanks for the suggestions and links. I think I'll do both and see how that impacts the sound level. I'll report back my results. Thanks again, everyone.

Zayd

[David Wong]

Bill Pentz web site also notes that using an 8ft length of HVAC flexible insulated flex duct can act as an effective muffler. Something I have been meaning to try myself.

[Rod Sheridan]

Reduces turbulance, hence noise...........Rod

[Ken Deckelman]

I built a muffler, and added some insulated HVAC duct to my system-made a huge difference, especially after the closet was completed. Pictures here: https://picasaweb.google.com/kdeckster/DC#

[Jim Neeley]

Ken,

Did you perform a sound level test afterwards too?

Jim

[Paul Wunder]

Jim,

The video below (from ClearVue Cyclones) shows a decibel reduction on a their 5hp cyclone from 84db to 62db after installing a simple closet lined with Roxul batts and an air baffle. No muffler or other external insulation. Worth a look.

http://www.clearvuecyclones.com/inde...22r316caf4hp83

[Ken Deckelman]

Ken,

Did you perform a sound level test afterwards too?

Jim

Yes, I did but never updated the albums as I still have a few small things to try, my last reading was about 75 at about 10 foot away and one gate open.