Noise control

Hello DWD,

Thank you for your great reply. You really covered a lot of topics and have helped with perspective building….these forums are great! The dynamics we are discussing are complex. This conversation is helping me sort out the variables. Thanks to you! And I hope this generates more comments to build greater common understanding on what is dynamic in coming up with dust collection solutions.

Some comments:

1. BALANCING DC PERFORMANCE TO MEET BUT NOT EXCEED OSHA REQUIRED CFM LEVELS.
Sounds like Im going down the same track as you, considering Oneida, then CV.
I did later find the fan curve url. My quick conclusion was that by the time I get down to the tool for my longest run/worst case static pressure situation, (tablesaw - 6”sp), I would get 1000cfm with the CV1800 and 950cfm with the CV1400. If tablesaw required minimum is 800cfm (from Bills website re OSHA required cfm) using 2 pickups on the tablesaw, then I would have 200cfm above minimum. My operating mode is to only run one blast gate and tool at a time. If I set my objective as achieving only OSHA minimums, considering my objective to keep sound levels down, (since high cfm at the blast gate = noise), how could I quietly get rid of this extra 200cfm?

The rest of my tools are at lower static pressure levels. For these, cfms are even more oversupplied relative to OSHA minimums. Again, anybody have any ideas on how to bleed off excess capacity, quietly?

Is going to a 3hp motor rather than a 5hp motor an option? I will have to ask. I only see fan curve for 5hp powered units. Maybe cyclone efficiency suffers with lowering HP? I will have to ask.

2. NOISE LEVELS – splitting out sources of the problem
“However, from Jameel's recordings and Jean-Guy's analysis, it appears the predominant tones are in the lower registers. However, most people seem to be more concerned with what appears louder, in the midrange and higher octaves.”

Hmmm, if the predominant tones are in the lower registers/frequencies, they are harder to take out using sound absorbing materials. I was looking materials sound absorption capabilities for building a cyclone room. What to line it with? So I though what frequencies am I trying to take out on the generation side of the equation. On the absorption/blocking side of the equation, soundproofing materials are rated by the frequencies they take out. See example on the bottom of this web page. This DUCT LINER product may be of general interest to all. Take a look at the specs.
http://www.knaufusa.com/products/co...handling_insulation/knauf_duct_liner_e-m.aspx (past whole url in browser if clicking does not work)

For sound sources, we have the cyclone in its space, and we have the blast gate/tool port situation out in the shop. Two different problems. The cyclone room seems easiest to soundproof.
But how to soundproof/sound reduce at the tool?
So far Im guessing:
a) large diameter ducts / blast gates, to lower the fps (feet per second) for the very high cfm’s delivered. (yes, we need 4000 fps, but isn’t that exceeded when cfms are so high with my static pressure levels?)
b) good pickup design
c) have some kind of way to open up the system to lower airflow to reduce noise….open a second blast gate….hmmm, what about the noise from that one as well.
d) lower horsepower for the whole system to match ones worst static pressure run to meet but not exceed, in the interest of noise reduction, OSHA minimum reaquirements?

As you say DWD…“It is apparent from Jameel's recordings, plus experience from Ed, Matt, Steve (Woodman), Nako and perhaps others that an insulated, dedicated room type structure does a decent job of killing most of the higher frequencies that seem most annoying. However, I might suggest with the amount of airflow recommended by Pentz, your desired numbers may be unattainable”

I would assume YES and YES.
Yes, for killing higher frequencies in the dedicated cyclone room, using soundproofing.
Yes, my desired db numbers unattainable…not for the cyclone if its in a soundproofed room, but at the tool. The reason for this is that tool ports are noisy too. Like 80db. But lets look at the difference between airflow recommended, and airflow delivered. The former is an objective. The latter is a consequence of ones personal static pressure setup for the run to each tool, and what sucking power you have on the DC as shown on the fan curve for each tool static pressure situation. How much over OSHA minimums is my layout, and how much noise is that extra causing? Something to consider if you care about noise.

3. HAPPY FAMILY
“But if your family is unhappy from the noise, it might help your case to note your super-duper collection system is keeping dust from going throughout the house.”
Absolutely! And keep me alive.

4. POWER LEVELS
there is an album in the photo gallery where someone switched from Oneida to ClearVue.
…..underpowered according the the CFM and flowrates Pentz recommends…
Yes, I saw that post and he was not clear on exactly what was wrong, but it looked like the 1.5 component that only does ~800cfm or so at ~3”sp (im not quoting exactly here) so that one does seem light and would only be good for short runs. But balancing power levels to meet multiple, conflicting objectives is what this discussion is about. The “how much is enough” question applies and there is a different answer for the 2 different objectives: maximum dust recovery and minimum noise.

Knowing your own static pressure situation seems key to strike the balance and size a unit to meet personal objectives.
 
Alas, more opining

Alas, more opining

RJ,

One little bit to clarify first, and you're making me reach way back to those three EE courses they made us mechanical types take to get our sheepskin. So this may be a little rough around the edges, for it has been, oh, 30 years.

The way I understand induction motors is they will turn at a constant RPM, and suck power as necessary to yield that RPM. In the case of a blower such as these, then, the amount of power being sucked is therefore proportional to the air being pushed. Thus if you throttle down the airstream, you'll need less power. Just because the machine is capable of drawing 5 HP and all that entails doesn't mean you have to use it all.

From what I gather reading others' posts, several have seen max. amperage readings for their Leeson motors in the 18 to 20 ballpark. Again from perhaps faulty memory, these numbers were achieved with minimal ducting and perhaps open exhaust, which means the maximum amount of air the impeller is ever going to see.

Power is amps times volts, so you get 3960 to 4400 watts. Convert to horsepower by dividing by 746 and you get 5.31 to 5.90 HP. That's electrical power to the motor. To get shaft output, an old rule of thumb buried deep in my memory recesses is multiply by 0.8 for motors. So shaft power delivered by the Leeson would be 4.25 to 4.72 HP.

Lower power, like 3 HP, means either you're not going to move as much air or the motor will be drawing its maximum amperage and still not making speed, the best way I know to burn out a motor. So obviously, machines designed to use 3 HP or less machines either use smaller fans or employ other means to throttle airflow.

But the other side of the coin is that while a lower power machine might satisfy your immediate need, it is at its maximum. Whereas a higher power machine would allow perhaps future longer duct runs.

In your #2 section, perhaps I wasn't clear. The meters and sound recordings seem to indicate, if I read Jean-Guy's analysis correctly, dominant noise is in the lower frequencies. Which I also saw when I ran Jameel's recording through a bit of trialware. Though the numbers that program didn't seem to match up too well with what Jean-Guy found with a more robust acoustic analyzer package, the trend seemed more or less the same.

But what I was driving at was the annoyance factor. We tend to hear and complain about noise when that noise is at mid to higher frequencies (say 1000 Hz and up) is actually lower in dB than a lower frequency, like a bass line.

Perhaps a better illustration would be the difference between a nice, throaty V8 rumble, think Chevy small block with a glass pack, versus the high pitched whine of an F1 motor turning at upwards of 20,000 RPM.

Another example: If you've ever stood adjacent to an airport runway, you soon learn to differentiate the sounds different jet motors make. An RR Spey, for instance, is dominated by exhaust rumble. It'll shake your kidneys at takeoff power. A GE CF6, on the other hand, is dominated by a higher pitched fan whine. And soon without looking you know which aircraft type just flew by. The CF6, at lower dB, is much more annoying, much more likely to get your, or your family's attention. That's all I was trying to get across. And the insulated closet should kill that whine.

But all that long windedly said, I should also point out the thread where Jameel and the Nickels discuss how their planers got significantly louder with dust collection: http://www.clearvuecyclones.com/Bullentin/showthread.php?t=789

As for your 4th point, I think you're right, the swapped out Oneida system was a lower power version. Its too late and I'm too lazy to go look it up for confirmation right now.

One other thought and I'll let you go. If you've been busily confusing yourself with all these posts and opinions, rest assured you're not the first. I, too, found the decision somewhat bewildering at first. I suffer from the "overanalyze" disease, spending far too much time scheming and weighing than actually doing. Which is possibly why I find Jameel's very rapid progress so amazing, but that's beside the point.

But, as I was saying, if you've been busily reading all this stuff, you probably figured out by now I have a Shopsmith and a bunch of their add ons. I don't trust the table saw function, know too many folks who've lost too many fingers on them, so also have a table saw. Most of the Shopsmith tools are set up for 2.5" ports, and aren't all that easily modified for anything much larger. So for those, I use the CV Mini to avoid overfilling a shop vac. And it does a remarkable job. Does it get all the dust, all the chips? No, but that's really a function of the motive flow supplied by the shop vac, which at best moves maybe 100 CFM. Certainly, though, it is no worse than the throttled down old Delta, and with a CleanStream filter in the Fein shop vac, I can be assured that even the fine stuff, if sucked up, won't then be blown back around the shop as the Delta does.

So depending on your tools, you might also consider the Mini, either first and see how it does, or in addition to a larger unit. Again, it depends on what you have and what you want to hook up.

Regards,

DWD
 
rj

We don't have a db meter or an engineering background, but we do have our cyclone up and running. Anecdotal evidence - the noise from the tool ports (with the exception of our jointer/planer discussed in the other thread) is not a big deal. Yes, you can hear it, but it isn't that loud and is not at all noticable once we turn on any of our machines. So I wouldn't worry about bleeding off that other 200 cfm or lowering your hp to have less cfm due to noise concerns. It really isn't that loud, and the extra cfm from a CV will collect the dust better.

Just our experience...
 
Noise Control

Noise Control

The folks that sell the recommended filters suggested I do the following, rather than building a muffler:
Make a circular fence of (what else?) fence wire. The stiff stuff.
The circular shape should be large enough to fit it over the filters with about 3 inches of dead space between the fence and the filters,all around.
Line this fence with old floor carpet. The thicker, the better It should be tall enough to leave about 10 inches of open space at the bottom and the top of the wire fence.
The walked upon surface of the carpet should face in against the wire.
This (muffler?) can be shortened with a good pair of shears to give it some additional tuning.
The filter folks swear this will work very well in reducing noise.
Has anyone tried this approach?
Also, my noise level also measured in the mid 90's without the filters attached.
 
Carpet

Carpet

Tom,

I can confirm that carpet helps by lining my 4 x 8 room that houses my dust collector and air compressor. I had tried just about everything else that has been thought of here and everywhere else prior to that. I haven't tried that one yet.

Matt
 
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