Dust collector blower noise reduction question ?

[Glenn Roberts]

I have made a dust collector blower (and cyclone) using Bill Pentz design and using a Clearvue impeller. made entirely from thick mild steel sheet. using a 3 phase motor.240v 50 hz. australia (not looking at using a speed drive at the moment- just straight on 3 phase eg: approx 2880 rpm) the impeller and blower are sized correctly for 50hz. according to Bill Pentz.

I would like to know if anyone has had any experience with reducing the blower noise by adding another 'gore point' inside the blower casing ( as mentioned in clearvue info) OR altering the outlet, inlet or internals of the blower.

Has anyone tried an adjustable helmholtz resonator on the exhaust duct or a 1/4 wave resonator?

I would very much appreciate any info, before I start testing. I would like to reduce the blower noise as much as reasonably possible. before resorting to mufflers and insulated exhaust ducts.

any info would be appreciated.

[Jim Andrew]

Have my cyclone in a storeroom, so cuts down on the noise considerably. Would consider building a lean-to outside the shop to house the cyclone. Don't know what the climate is like where you live, but I put a blast gate on my exhaust so I can exhaust outside most of the time, when it is heating season I can close it and use a filter. No neighbors close by to complain.

[Glenn Roberts]

Thanks Jim, I intend to exhaust outside but the cyclone must be inside and I don't want to build a cabinet around it. i just don't have the room. hence why i want to make it as quiet as possible with other means. including adding sound deadening on it etc.

[John K Jordan]

Thanks Jim, I intend to exhaust outside but the cyclone must be inside and I don't want to build a cabinet around it. i just don't have the room. hence why i want to make it as quiet as possible with other means. including adding sound deadening on it etc.

The think I read what helps the most is to sound-insulate the exhaust duct. I use the 5hp ClearVue and it does sound like a freight train. I haven't tried modifying it to reduce sound. Fortunately I was able to incorporate an insulated closet into my shop plans for the DC and air compressor so mine is quite subdued. I know some people put sound insulating panels around the whole thing where space is tight. Did you check the ClearVue forum for sound reduction ideas?

JKJ

[Glenn Roberts]

I have researched the clearvue forum, but with only limited success.

[glenn bradley]

I did get the inline muffler for my cyclone when purchased. I noticed little improvement from this method which placed a foam lined container between blower and filter. This is not a cure for your problem but, more an example of something that did very little versus the cost/effort.

[Mark Donnici]

I recently installed a 5 hp SDG in my crowded two car garage shop of approx. 475 sq. ft. The first time I turned it on I could not believe the noise (104 db) as well as the turbulence from the discharge air through the filter. The unit has to be in the garage and could not discharge outside. Although I did not want to I built an insulated closet around it with a "folded plenum" style discharge at the top. I used 2 layers of soundboard, 1 layer of OSB, and R13 in the stud bays and ceiling as well as on the fan housing and duct to the filter, with 3/4 inch ply on the outside. I lost 23 sq. ft. of floor space but reduced the noise level to 69 db. I am slowly regaining the lost sq. footage by more efficient use of space and taking my hoarder medication. My point is the surest way to reduce the roar was to enclose it....even though I really didn't want to.

[mark mcfarlane]

I recently installed a 5 hp SDG in my crowded two car garage shop of approx. 475 sq. ft. The first time I turned it on I could not believe the noise (104 db) as well as the turbulence from the discharge air through the filter. ....

Did you measure 104 dBA or dBC? How far away from the exhaust was your meter? Slow or Fast setting on the meter? Oneida claims "Noise Level (with built-in silencer): 80-82 dBa at 10ft" for this unit. dBC tends to give a higher number with sources with low or high frequency content. dBA is biased to mid-range frequencies

[Mark Donnici]

I used an inexpensive digital sound level meter. I used the same meter both before and after enclosing the unit. I measured 104 dBA at about 5 feet from the exhaust. The meter does not have fast/slow settings . I measured 69 dBA at about 6 inches from the enclosure. My filter has the "built in silencer". My experience with Oneida was good. I did spend many hours reading the D/C threads on SMC and many other people commented on the unexpected noise level.

[Larry Frank]

I have that same 5 hp SDG in my garage and it is not too bad. I used an app on my android phone and got 80 dba. It is certainly much quieter than several of my other tools.

[mark mcfarlane]

I used an inexpensive digital sound level meter. I used the same meter both before and after enclosing the unit. I measured 104 dBA at about 5 feet from the exhaust. The meter does not have fast/slow settings . I measured 69 dBA at about 6 inches from the enclosure. My filter has the "built in silencer". My experience with Oneida was good. I did spend many hours reading the D/C threads on SMC and many other people commented on the unexpected noise level.

Thanks Mark. I'm probably missing something here. You measured 69dBA at 6 inches and 104 dBA at 10'? The physics suggest that the closer you are the louder it should be.

Outdoors, suspended in air (free field), the falloff should be 6dB per doubling of distance, so your 104dBA measurement @ 5' should be 98 dBA @ 10'. Oneida says it should be 80-82dBA at 10'. You are measuring ~4 times louder than what Oneida published (10dB is ~ a doubling in volume), so something is wrong here.

The -6dB dropoff might be reduced to -4dB in an indoor shop,... unless maybe you are mounted in a corner.

FWIW, for folks publishing sound pressure measurements in the forum, they are entirely meaningless without including your distance from the source and whether you used dBA or dBC.

[John K Jordan]

Thanks Mark. I'm probably missing something here. You measured 69dBA at 6 inches and 104 dBA at 10'? The physics suggest that the closer you are the louder it should be.

I thought the same thing on first reading, but when I read it again I noticed the "I used the same meter both before and after enclosing the unit" - the louder reading was probably without the enclosure.

This is similar to my experience with a 5hp ClearVue with and without my sound-insulating enclosure. I don't remember the numbers, but difference is like standing next to a freight train with the whistle blowing vs being able to have a normal conversation a few feet from the closet wall. I built a 4x8 room with 6" staggered stud walls. Since the 5' double steel door is the weakest insulated point I had it open into another room away from the wood shop area.

JKJ

[mark mcfarlane]

.... I built a 4x8 room with 6" staggered stud walls. Since the 5' double steel door is the weakest insulated point I had it open into another room away from the wood shop area.

JKJ

John, That's a good idea about having the door open somewhere else, I may change my plan, except it might be a nuisance to check if the bin is full, and I don't see people having much luck with the 'bin full' sensors.

My current plan has the DC in a little room the protrudes into an attached 2 car garage (30' deep). Maybe I should just skip the mechanical room altogether at first and just put the DC in the adjacent attached garage, with the shop door 20' away from the DC. Then I can build an enclosure later if needed, and make it 'just the right size' after the DC is installed. That would save some money on the initial build and I may find that I don't even need the enclosure, but it would probably be really annoying to the neighbors when the garage door gets opened,...

[Mark Donnici]

Thanks John.
Thanks Mark. I appreciate the physics lesson.
My post must have been confusing.
Here is a summary:
1. D/C unenclosed=hecka loud.
2. D/C enclosed in insulated closet=hecka quiet.
3. Did not want to enclose because of small shop ( just like the OP ), but very glad I did.