Dust Collection Noise

[Jim Becker]

I'll post pictures tomorrow. It's a 5hp clearvue cyclone. I have safe n sound 3" rock wool in between the studs. I have 6" inlet going to the cyclone through the side of the shed and an 8" exhaust leaving the shed.

The insulation will certainly help with noise radiated from the motor, etc., but it's not going to do anything for the direct sound transmission that's been mentioned already. You need to deal with the exhaust by making it change direction at least once, if not twice and muffle that sound to reach where you need to be. Your outlet duct size can be substantially larger to compensate for reverse bends, etc., too.

[matthew lippel]

I was using a phone app. I realize it's imprecise but I wanted to provide some quantifiable data. However, qualitatively, if I'm by the exhaust, I have to yell to hear anything. I'm looking to achieve the results you're having Chris.

Also it's a brand new Clearvue. It has the block in the chamber.

[John K Jordan]

I was using a phone app. I realize it's imprecise but I wanted to provide some quantifiable data. However, qualitatively, if I'm by the exhaust, I have to yell to hear anything. I'm looking to achieve the results you're having Chris.

Also it's a brand new Clearvue. It has the block in the chamber.

A stand-alone sound meter might be worth having in the shop. I have this one and although inexpensive, I was surprised at how well it performs. https://www.amazon.com/gp/product/B000EWY67W
I tried one for my phone and it worked about as well as I feared...

I keep instruments to measure sound, light, temperature, wind, pressure, RPM, frequency, and various electrical parameters - I don't use them all every day but they are so handy on occasion.

JKJ

[matthew lippel]

IMG_7822.jpgIMG_7821.jpgIMG_7819.jpgIMG_7820.jpg

So here are the pictures and some things to note:

I have a vent positioned on the bottom (seen in first picture) to provide the shed with cool air. The exhaust, which I KNOW is the major culprit in noise pollution is utilizing the why so I can take advantage of the Venturi effect. In short, faster air has a lower pressure and the stagnant, slower moving air has a higher pressure thusly the hot air by the motor is being sucked out with the exhaust and is replaced by the cooler air from the vent at the bottom. A Venturi tube does utilize a constriction to speed up the air and maximizes this effect, but I don't need major suction, this provides me with about 200 cfm which is more than enough to vent the closet. That said, it looks like I'll have to figure out another way to vent the heat since I will be likely modifying the exhaust.

So some questions that still remain:

(1) How do you vent the heat generated by the motor without disturbing the sound proofing

(2) Does my muffler have to be in the same plane as the impeller or can I have the exhaust head towards the floor and achieve noise mitigation?

Many thanks,
Matt

[John K Jordan]

Matthew, Much clearer now. You don't show the other side of the shed. Does your exhaust vent into the open air just past the wye? That would be very loud!

I assume you studied the other recent thread about muffling the sound on an outside vent (since you posted the question about cooling there). I included a diagram of my air baffled air return in a message there. My experience with cooling: my 5hp ClearVue is in a 4x8 insulated closet (with staggered stud construction). I exhaust through the Wynn filters into the closet. This creates a positive pressure in the closet which exits through a vent near the floor and is forced up and through a baffled return duct I made from plywood. I snaked the duct through the ceiling trusses and the return is into the shop through a ceiling vent. Standing right outside the closet and under the vent I can carry on normal conversation and still hear a whisper. I think for sound, changing the direction of the path several times is the key since sound is absorbed at each turn. (I sprayed the inside of my plywood exhaust duct with a flexible coating, made multiple turns, and added some internal baffling.)

My closet has no other venting. The air gets warm but evidently there is enough circulation within the closet to keep the motor cool. I touched it once after running and it didn't seem too hot but I didn't measure the temperature - if you want I can tape a thermocouple to the case and measure the temperature the next time I run it. You might look up the specs on the motor and see what the manufacturer's recommends as the maximum continuous operating temperature.

I know from reading the ClearVue and other forums that some people put such a return vent high on the closet wall then use the space between the studs to run the duct down and then into the shop. The plan here is to pull warm air directly from the vicinity of the motor, still relying on the positive pressure in the closet to circulate the air past the motor. These installations of course, unlike yours, are not vented directly outside.

This is my opinion based on reading and thinking but not on direct experience: I don't think it matters how the muffler is orientated. The airflow exiting the cyclone is under pressure and can easily go through bends without decreasing the efficiency as long as the cross-sectional area is large enough. You can make it much larger than needed to be sure. Note that the default installation of the cyclone uses a short connection which quickly curves downward into the filters. I think you could start your muffler directly at the output of the cyclone and send it downward inside the closet before venting. (To fit the space, the turn could even be a well-insulated box.) It would be easy to try the insulated flex HVAC duct - connect it to the outlet and curve it down towards the floor. From what I read on the ClearVue forum, the longer the muffler is the better.

For cooling, something easy to try might be to build an exit duct or simply use another length of large insulated flex duct to pick up air high in the closet (perhaps somewhere near the motor) and move it to the outside. (The air will be pumped outside due to the positive pressure in the closet.) All this would be easy enough to try, holding the duct in place with wire and duct tape before investing the time in a careful installation.

As for duct size, bigger is better. If using the flex, I might use or make a short sound-insulated connection between the cyclone and the duct. You can buy a 25' length of 10" insulated flex duct at Home Depot. http://www.homedepot.com/p/10-in-x-2...X300/100142376 If I were doing this, I'd get that, cut it in half, hook one half to the cyclone and dump the air somewhere into the closet, and use the second one as an exhaust pickup and vent outside. That wouldn't be a too-expensive experiment!

If you don't hear sound coming through the exit vent but you still hear it through the closet walls, another layer inside the walls and doors might help. Note that another source of sound is the wall the cyclone is attached to. If it is acting like a sounding board, some isolation might help. Some people build a free-standing frame to support the cyclone to avoid transmitting sound to a wall.

(Be sure to protect the end of the duct from rodents, birds, and wasps, at least when not used for extended times!)

JKJ

I have a vent positioned on the bottom (seen in first picture) to provide the shed with cool air. The exhaust, which I KNOW is the major culprit in noise pollution is utilizing the why so I can take advantage of the Venturi effect. In short, faster air has a lower pressure and the stagnant, slower moving air has a higher pressure thusly the hot air by the motor is being sucked out with the exhaust and is replaced by the cooler air from the vent at the bottom. A Venturi tube does utilize a constriction to speed up the air and maximizes this effect, but I don't need major suction, this provides me with about 200 cfm which is more than enough to vent the closet. That said, it looks like I'll have to figure out another way to vent the heat since I will be likely modifying the exhaust.

So some questions that still remain:

(1) How do you vent the heat generated by the motor without disturbing the sound proofing

(2) Does my muffler have to be in the same plane as the impeller or can I have the exhaust head towards the floor and achieve noise mitigation?

Many thanks,
Matt

[andy bessette]

JJ--good post.

[Alan Schaffter]

Here are my recommendations- some may repeat what has been said, some are new:

1. First be careful about your enclosure - make sure there is plenty of room around the motor and good air circulation- you don't want to overheat it or cause the bearings to wear prematurely.

2. In view of #1 make sure the enclosure has plenty of free space at the top.

3. Eliminate all means where vibration can be transmitted to the outside.

4. Connect the inlet and outlet to the cyclone and outlet of the blower to your ducting with Ferco fittings (make your own using truck tire inner tube- works great!)

5. build the enclosure walls with 2X6 top and bottom plates, offset the 2x4 studs and weave in rockwool insulation. Insulate the door too.

6. Do not build a baffle muffler- adds too much SP/robs too much CFM. Build a "glass pack" style flow through exhaust muffler- make an inner "tube" from square weld hardware cloth, lightly wrap it with layers of glass or rock wool until it is twice the diameter or more, wrap the outside with flashing or something to protect the glass wool.

7. Aim the muffler exhaust towards the ground or a void

7 of the cycConne

[matthew lippel]

So I tried the quick and easy approach that Chris Parks recommended. Got 25ft of 8" R6 ducting. Immediately the screaming cyclone quieted to about 60db. My anemometer doesn't go above 5600 ft/s and it goes blank anytime it exceeds that. This happened when I measure a 6" duct on the inlet side without any attachments to the exhaust. Measuring the same line WITH the 25ft of ducting attached to the exhaust I'm seeing about 5500 ft/s which translates to the 1000cfm. I think it's fair to assume I've created some back pressure that decreases overall performance. That said I'd be fine with anything around 1000 for my small shop. Thinking I could improve the performance I cut the 25' duct length to 18'. The noise shot up to 70dba. Thinking I didn't want to spend much more time on it I purchased another 25' duct and put it on. Still reading 70 dba. I think some of the noise is created by some of the air hitting some of the loose plastic in the duct by the opening. I may try and attach a 90 degree turn at the end aiming at the floor.

I'm willing to build the glass pack muffler but I'm wondering if I'll have more consistent and equal or better performance. I saw somewhere someone built a 4 ft version to the ground and then "U'ed" it back up and out using some insulated duct.

What do you guys think?

[andy bessette]

...I may try and attach a 90 degree turn at the end aiming at the floor...

Avoid 90* turns. Instead use two 45*'s.

[Alan Schaffter]

Yup, no 90's, just gently curve the duct. Remember, that duct has wire coils which make ridges on the inside which create friction- SP- and lower CFM. Make the length as short as possible no longer than it takes to achieve the desired dB reduction.

[John Jenkins4]

It may be that 8" duct is part of the problem. I bet if you used 12" duct that you'd have better results with a shorter run. 8" is about 50 square inches while 12" is about 113 square inches. That's a lot of extra space for sound to bounce around in and dissipate. Also no back pressure issues.

I've got about eight feet of 12" duct as my exhaust and it works very well.

[John K Jordan]

It may be that 8" duct is part of the problem. I bet if you used 12" duct that you'd have better results with a shorter run. 8" is about 50 square inches while 12" is about 113 square inches. That's a lot of extra space for sound to bounce around in and dissipate. Also no back pressure issues.

I've got about eight feet of 12" duct as my exhaust and it works very well.

As I mentioned in an earlier post in this thread, Home Depot (and others) carries a 25' length of 10" duct. I think this would be sufficient but the 12" you mention might be even better. As for the 90s and bends mentioned, every time the duct changes direction the sound is dampened. Matthew could use some gentle "S" curves inside the closet. I used plywood instead of flex but I changed direction 6 times, making the cross-sectional area much larger than needed so back pressure would not be an issue. As I mentioned, I don't hear sound coming from the vent.

JKJ

[Peter Aeschliman]

I recommend building a baffle box with sound-proofing material (i.e., egg crate foam) inside of it.

If you design the box correctly, you can limit the CFM loss. For example, an 8" inlet with a 12" outlet, with the cavities inside the box that are never smaller than the area of the 12" outlet. The box will have much less pressure inside of it than your 8" duct, thus somewhat limiting the negative impact to your CFM. You will lose CFM for sure- that's somewhat impossible to avoid.

I think one of the main reasons for limited results with those "glass pack" style mufflers is that they don't change the direction of the air. So lots of the sound waves just pass straight through it. Some sound waves get absorbed for sure, but lots of the sound waves goes straight through it without hitting the sides. So the key is to change the direction of the air, causing the sound waves to hit noise-absorbing material, while limiting the air restrictions.

[Chris Parks]

Matt, did you have a look at the link I sent you? Anemometers are a waste of time in reality, they interfere with the flow and the flow is different in the duct to the duct entry. Bell mouth entries into ducts will markedly increase the flow of any duct and the pick up area as well.

[Bill Jobe]

A couple of us suggested isolating every piece (of metal) with rubber.
I just finished repairing my pickup after a shackle broke. I took the bed off to make it easier to get to and so I could rust proof the frame and the bottom of the bed. When I took the bed off all 6 bolts holding it on had rubber between the bed and frame.

Also, I haven't read anything about running your exhaust underground. Lots of potential there, I think.
Perhaps several feet of large diameter tubing of some sort zig-zagging underground. Just some thoughts