Noise control - 91 dB

W

wavery

New member
I have installed my CV1800 behind the back wall of my shop and run the 90 deg exhaust transition through the wall and into the filters inside my shop.


The noise level 6 feet from the filters is 91 dB. This was in a 20' x 18' shop, with concrete floor, and all windows and doors closed. I have been thinking about starting the noise reduction process by putting some acoustic insulation around just the transition piece. Has anybody tried something like that? Does anyone have a sense of the acoustic insulation properties of the filters? Can anyone share experience on insulating around the entire filter assembly yet having the right air flow out of it? Any ideas appreciated.

PS: I tried to upload a pic in both .jpg and .pdf format and was getting some weird errors. When trying to upload the .pdf I got some kind of "could not find server error..."
 
Is there any way that you can build an enclosure around the entire system? My CV is in the corner of a 13' x 23' shop. I built 2x4 stick walls with fiberboard inside and fiberglass insulation. There is a 26" by 52" access panel for the barrel plus one entire wall is removable if I need to clean the filters.

The sound level measures between 70-75db in various locations around the shop. Most of the noise appears to be air movement through the PVC ducts. I am quite happy with the noise level with a full enclosure. I suspect that a partial enclosure around just the transition piece will leave you only partially satisfied.

Steve
 
thanks for the response. Yeah, I could build and enclosure around the entire filter assembly. That is probably the best way to go. If I did, I would use acoustic insulation. What has to be thought through is getting the air through the enclosure and back into the room. I recall that good standard practice is to make the air (hence the sound) turn 180 degrees or more entering the room. So for 6" ducting I would probably want 2x-3x the area of the 6" duct as air exits into the room to get reasonably unrestricted flow.

Regarding the noise from the ducting, my intake goes up into the crawl space above the shop right after leaving the DC, then drops back down in 3 locations in the room. So at lease some of the duct noise is buffered from the shop.
 
John Samuel's Post

John Samuel's Post

You might want to take a look at John Samuel's post, "It Begins.." on this same Noise forum.

He vents outside and claims to achieve 65db in the shop even though the cyclone is not enclosed. Most of the noise is going into the exhaust port and outside in his case. If you have a filter, most of the noise will come out of the filter. This indicates that controlling the noise from the filter is the most important thing you can do.

Dale
 
VermontDale said:
You might want to take a look at John Samuel's post, "It Begins.." on this same Noise forum.

He vents outside and claims to achieve 65db in the shop even though the cyclone is not enclosed. Most of the noise is going into the exhaust port and outside in his case. If you have a filter, most of the noise will come out of the filter. This indicates that controlling the noise from the filter is the most important thing you can do.

Dale
Click to expand...

Very interesting. It would certainly be a lot more convenient to just enclose the filters. The airflow should probably go past the motor to keep it cool, then back down and around a few bends before exhausting it back to the room. According to this theory, the drum could be left in the open for easy access.

Steve
 
Cooling motor

Cooling motor

It isn't necessary to blow the air back onto the motor. The motor has a built in fan which is capable of cooling the motor unless it in an enclosure. In addition, a lot of motor heat gets carried away by the air flow through the blower. Note that John Samuel doesn't have his motor enclosed.

However, it the motor is enclosed you do need to blow the air across it.

Dale
 
Good point Dale. However, if you do enclose the filters, then you can provide extra cooling to the motor for almost no additional cost.

Steve
 
More on 91 dB

More on 91 dB

This is a follow-up to my original post that some might be interested in. The attached file shows pics of my dust collector, with the main "guts" behind the wall of my shop, with the filter inside my 20'x20' shop. A Radio Shack meter showed 91dB 6' from the filter, and 84 dB about 2' from the impeller (behind the shop), clearly indicating that most of the noise comes through the "exhaust". The last page of the attachment shows the frequency distribution of the noise in the shop. It appears to show a broad frequency range of sound distribution. Incidentally, an acoustics book I have shows the human ear is most sensitive frequencies in the range of about 200 Hz to 10 kHz

It looks like to cut the noise in my shop I am going to have to box in the filter with acoustic insulation and an appropriate circuitous air exit, or reconfigure the collector to run the exhaust through some kind of pseudo-muffler before running it into the filter.

Finally, the sound levels were measured with all doors and windows closed. When I opened all the windows, and opened the roll-up door 3/4's, the sound level dropped by about 2 dB. All the openings were behind the microphone. I assume some benefit of less reflected sound.
 

Attachments

  • Cyclone_Acoustics.pdf
    583.9 KB · Views: 5
Filter enclosure

Filter enclosure

Hi waverly,

We just finished the filter stack enclosure yesterday. It is about 2' square and 8' long and will be mounted next to the ceiling so it doesn't take floor space. Only the filter stack in enclosed.

The preliminary noise measurements are very encouraging. We will find out for sure when we install the cyclone and ductwork.

We hope to finish the installation later this month. I will keep you posted on the results.

Dale
 
filter enclosure

filter enclosure

I look forward to seeing details of your enclosure, especially how you vent the return air through it.

Bill
 
VermontDale

VermontDale

I am sad to announce that VermontDale passed away on Friday evening. His contribution to this forum and to Clear Vue Cyclones will long be remembered and valued. His noise cancelling engineering works incredibly well, and I know many have walked down this path and found similar results.

It was my personal joy and privilege to have known Dale.

Thank you Dale!

Rest in peace, James.
 
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