CV1800 w/ Acoustical Foam Absorber

M

Mike Goetzke

New member
I spent about 90 min. wrapping my new CV1800 with the subject material. It is an acoustical foam with a heavy rubber backing:

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Before I wrapped it I just held the sheet in place like a curtain. Guess what, the curtain reduced the sound a little but surprisingly the custom wrapping made no improvement even with the extra piece around the outlet. The sound really isn't much worse than my Jet 1100 that I'm replacing. Guess if I want to reduce the sound further I'll need an enclosure.

Anyone ever try a Helmholtz resonator on one of these things?

(Good thing experimenting is fun.)

Mike
 
I took a piece of r-19 unfaced insulation and loosely wrapped it around the upper filter and transition and could tell a slight reduction in noise.
 
I ended up just building a small closet around it and padded the walls with some mineral-wool insulation I found at a local Menard's. If I stand next to the cyclone it's about as loud as my furnace running. If I walk around to the suction side it's still a little loud, but, that means lots of air flow. It's now even much quieter than my old Jet 1100.
 
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Mike Goetzke said:
I ended up just building a small closet around it and padded the walls with some mineral-wool insulation I found at a local Menard's. If I stand next to the cyclone it's about as loud as my furnace running. If I walk around to the suction side it's still a little loud, but, that means lots of air flow. It's now even much quieter than my old Jet 1100.
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Sound is a strange thing to understand. I'm more than satisfied with the sound level of the cyclone throughout my garage/shop. I have an attached garage on a tri-level house. I had the cyclone running and went in the house. When I walked down the four steps leading to the entrance door I could feel/hear a low freq. resonance. I could even hear it in the house with the door closed. I opened the garage overhead door and it made no difference. I even let the air exhaust the enclosure at a different location and again no change.

Any suggestions?


Thanks,

Mike
 
The low frequency resonance that goes beyond your shop is most likely due to vibration being transmitted from your cyclone to the house structure. How is your cyclone mounted?
 
arthurs said:
The low frequency resonance that goes beyond your shop is most likely due to vibration being transmitted from your cyclone to the house structure. How is your cyclone mounted?
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It is hung from the ceiling with two 1/2" threaded rods. I have a vibration dampener mounted on the motor mounting plate:


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Like I said the sound level is very acceptable throughout my garage/shop but the low freq. sound is apparent when my ears are near the floor level of the garage as I walk down 4-stairs into the house. I did modify the exhaust air from the cyclone and it made no difference. Maybe I should look to see if any parts of the cyclone are touching the walls of the garage.

Mike
 
You probably need a Softer dampener, something with more elasticity to absorb the higher amplitude/low frequency vibrations. Shorten the rods and add springs to further isolate the vibrations.
 
Indeed noise and vibration will find the path of least resistance, and exploit it as the weakest link in the chain. It's hard to tell how effective your present dampener really is, perhaps get a better one. Also look at any other parts of your cyclone that touches your house's structure, and come up with creative ways to isolate the vibrations.

Here's a very useful source of vibration isolation parts, and yes, they do sell direct to the end user (minimum order $100 I think):
http://www.kineticsnoise.com/
 
I had my wife and kids listen and they don't think the sound is annoying at all.

My mounts are pretty flexible. One other thing I might look at is when I installed the filters I really hammered in some shims between the clean-out box and floor. Maybe I can temporarily remove them to see the effect.

I'm getting excited to use this beast on a new project. I'm picking up some rough sawn white oak on Saturday to build a new entrance door with two sidelights.
 
Resonators

Resonators

Mike mentioned resonators. I don't think a Helmholz will work at this frequency (345 Hz) on an 8" pipe. A 1/4 wave side branch might work. I want to try it. A standard side branch design (like a pipe tee) probably wouldn't work. It would have to be a circumferential type (360 degrees). It should be placed in a 1/2 wave increment of length from the blower's gore point (20" or 40"). A resonator reduces the tone peak level and produces 2 smaller ones at different frequencies that are much lower levels (less objectionable). Sometimes these things work and other times they don't provide much benefit. You just have to experiment to find out. I plan to make a design that can be tuned with ring inserts until I find the best length. If you just make a theoretical design, it probably will be a little off frequency.
 
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