Noise Abatement: Best Practices for those NOT venting outside

[expo123]

Hi all

I am close to placing an order for a new CV-1800... I gather from reading several of the posts here that for those venting back to the shop through filters there are three common practices for reducing noise:

1) Building a closet/enclosure around the unit and soundproofing with something such as Roxul, or acoustic foam panels, etc.

2) Adding a folded baffle or chimney to the air return to muffle the sound coming from within the enclosure.

3) Adding a length (~8ft) of flexible insulated HVAC ducting between the blower exhaust and the input to the filters.
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Have I missed anything important?

I am committed to doing #1 and #2 above, but I am not certain whether there is any real motivation to also including #3... any comments? The downside I see for my specific application of adding the HVAC ducting is the additional space required to contain the duct inside the closet (ie larger enclosure means less shop space in my small garage shop!!).

Thanks in advance!!
Andy

 

[Steve P]

Hi Andy,

I agree that you certainly want to do items #1 and #2.

I built a 28" by 45" by 10' tall enclosure in a corner and it helps a lot with the noise. I used simple 2x4 construction with fiberglass insulation inside. The inside walls are a fiber board insulation from the big box stores. I think it is called soundboard. The outside is 1/4" wood paneling. Sheetrock might be slightly better for noise isolation.

The filters are in the corner with a 1/4" wood panel deflecting air up past the motor and back down past the drum. The exhaust goes past the barrel and flows about 6' behind a wall mounted workbench before going back to the room. This seems to be enough to isolate the noise. A folded baffle might be even better.

I used a 55 gallon plastic barrel with wheels. This just barely fits into the opening with about 1" of clearance. I have a 25" by 55" access panel that can be easily removed to empty the drum. The filters and the rest of the unit are behind removable covers as well, but they are screwed down and slightly harder to access.

My sound measurements are around 70-75dB depending on where I stand and how many blast gates are open. Most of the noise appears to be air sneaking past closed blast gates. I rarely wear ear protection until I turn on a power tool.

Hope this gives you some ideas. One last piece of advice: Install the CV completely and build an enclosure afterwards. Mine is very tightly packed. It would have been a lot harder to fit in an existing closet unless you make the closet huge.

Steve

 

[Mike D]

I realize this thread is a half decade old.... But does it make sense to use some snaking insulated duct as the exhaust from my CV closet? Or should I make a baffle instead? This is assuming my CV is using the standard filter setup inside the closet.

 

[Rushton]

Mike, I used 15' of insulated flex hose for my exhaust connection to my filters per Bill Pentz's suggestion. So far, it's working well. It didn't make a dramatic improvement in noise reduction, but it was noticeable. In my case, I used the 10" R-8 flex duct from the Home Depot. I don't have any way to compare to a baffle.

 

[Mike D]

So you have the duct between the cyclone and the filters?

 

[Rushton]

Yes. Here's a sketch of my setup:

My installation is in a low-ceiling basement shop, so I've mounted the filters side-to-side under a manifold and I use the straight transition out of the blower assembly. With the 10" diameter flex duct I'm using, the outlet diameter is a bit too small but I was able to simply tape down the flex duct to the outlet.