Noise levels of various milling machines

I'm aware there are other sound apps, like Physics Toolbox, but we don't know if they have the same sensitivity as the iPhone NIOSH app. So effectively, unless someone goes through the effort of calibrating relative to the iPhone, we don't know the relative sensitivity for the non-iPhone apps. Hard to compare outputs, if there's no known cal factor between them.

It's not that it can't be done, but measuring sound levels and frequencies that are quantitative (and perhaps traceable) isn't as easy as it may initially appear. And that's leaving out the human factor where individuals perceive / hear things in different ways. Some sounds are more annoying that others and that varies by individual.
 
All I can offer right now is a video of my Steinel milling some O-1. This is with a 50-50 mix of gear oil and STP in the head to quiet it. Its not in a bath, it is a total loss system but this is half the amount of noise it makes with iso68 lube.

Without my 50-50 mix its too loud to hear what your doing.

 
WobblyHand said:
I'm aware there are other sound apps, like Physics Toolbox, but we don't know if they have the same sensitivity as the iPhone NIOSH app. So effectively, unless someone goes through the effort of calibrating relative to the iPhone, we don't know the relative sensitivity for the non-iPhone apps. Hard to compare outputs, if there's no known cal factor between them.

It's not that it can't be done, but measuring sound levels and frequencies that are quantitative (and perhaps traceable) isn't as easy as it may initially appear. And that's leaving out the human factor where individuals perceive / hear things in different ways. Some sounds are more annoying that others and that varies by individual.
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Unless you have an external calibration source, any sound intensity app is going to be relative. There are too many factors that influence the measurement. Frequency response of the microphone and the internal amplifier, directivity of the microphone being two, off hand. For those interested, here is a study of suitability of various apps. https://pubs.aip.org/asa/jasa/article/135/4/EL186/968109/Evaluation-of-smartphone-sound-measurement

Actually in my experience, the noise generated during milling far exceeds that of the drive train. My Tormach mill doesn't start to get excessively noisy until I exceed 5,000 rpm. Most of the noise above that speed is due to the internal cooling fan in the motor.
 
I would be surprised if the noise level of the exact same model machines were also exactly the same. Gear quality, design, PA, and mesh make a difference and just a slight adjustment or misalignment can change the noise level. I doubt these machines have the ideal QC to match gears and adjust the contact if slightly off. The oil used and viscosity can also affect the noise level. Pulley alignment and quality can also impact noise.on the belt side. There are lots of variables. Reducing the number of gears can reduce the noise but often the fewest gears are on the top end where the cutters drown out the machine. I'm not saying the exercise isn't valid, but I'd not expect to base any purchase decision on it. Dave
 
First due a complete and proper investigation
inspect the gears ( ware, gear mesh, ect)
disconnect/ remove the drive Gear, run the motor record the noise
measure the gear gap (a thin strip of paper)
test each gear engagement.
some gear are poorly cut and make excessive noise, most noise can be controlled or minimized
 
I think the OP just wants a rough idea, not an absolute number.. too many variables to be really precise
On another note, I want to see a smart phone app for testing watermelons for ripeness. You input the variety and size.
You put the phone next to or touching the melon and it sends sound waves into the fruit- the software analyses the sound/vibrations coming back and gives you a yay or nay
So many times I've tried to grow sugar babies and picked them too soon
:)
 
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Mill manufacturer and Model: Precision Mathews PM-833-TV
Mill Type: Benchtop, VFD & belt drive
Any modification to the spindle drive train: none
Where was noise measured: 3 feet in front of spindle at head height

Spindle speed 60 (RPM) Noise 50 (dB(A))
Spindle speed 450 (RPM) Noise 62 (dB(A))
Spindle speed 1500 (RPM) Noise 75 (dB(A))

measured using iphone app "dB Meter Pro" (pretty sure that is not NIST traceable :).
 
Best way to do this to get real, meaningful data, is with a "traveling meter."

Everyone chips in to purchase a decent meter & then it gets shipped around to everyone interested in adding data points to a database. Seems to work well in other hobbyist realms. e.g., the electronics guys have been sending around calibrated (and fully traceable) voltage/current/frequency/etc references for quite some time so they can calibrate the function generators/voltage sources/power supplies/o-scopes/whatever else they have sitting on the bench at home. All b/c calibrated stuff is very nice to have but it's ridiculously impractical b/c it would cost a freaking fortune to calibrate some home labs.

An RTA with data logging would be my choice. Not sure if anyone makes a dual use data recorder/analyzer that can handle a microphone for sound levels & an accelerometer/velocity sensor to measure vibrations would be the bees knees. Unfortunately it would not, in any way, shape, or form, be cheap to acquire.

But vibrating machine surfaces are what turns the mechanical energy into sound waves & while they are affected by how a machine is anchored (or not anchored)/exactly what something like a bench top machine calls home, there is nowhere near the variation seen in sound levels caused by the environment the machine is in.

So it would really be nice to have both.

Also, a standard test plan. None of this "distance/location = ?" It's absolutely crucial to have a standard test plan & it must be rigidly adhered to. Add as many test locations as you'd like, but there has to be some kind of minimum that everyone has to provide.

If this is something many are interested in I can help with a test plan/parameters.

Also, it's extremely far from ideal, but I'm willing to donate an old radio shack sound meter to the cause. No clue if it contains a mechanism for calibration, but it would definitely help.

W/o it you can't get any absolute readings but if everyone uses the same meter & the same testing procedure it will provide data that can be directly compared. There's still the problem of environmental variances so a full description/pictures of the machine location would definitely be included in the test plan. That becomes fairly useful data as soon as 2 people with a Bridgeport, one in a garage & one in a concrete basement, submit data.



Anyway, yeah, if someone corrals a group of people I'd have no problem donating my cheapy meter.

But with the ginormous number of more modern meters at every price point, that would probably be a much better option. ~$200 will get you a pretty good meter & should be easily attainable if the number of people interested make this a worthwhile venture.

Sent from my SM-N975U using Tapatalk
 
This subject strikes a chord with me (accidental groan pun), since my ears helped me feed my family. I spent many years repairing organs and tuning pianos. It is not surprise that I rarely go to concerts that used megawatt amplifiers. However, I did for a number of years worked as a stage manager for a symphonic orchestra. Since then, I have learned a lot about room acoustics. sound theory, etc. Now, after all this, what does this have to do with machinery. A lot. A well-tuned and properly lubricated machine should purr not squeal.
For a couple of years, I worked as a projectionist for a movie theater. They had these old Century projectors that had the old carbon arc lamps. They ran beautifully but were also noisy not loud. If something went wrong, such a jumped sprocket. You knew immediately by the sound. Running a lathe or mill is no different. When you cut metal, it should have a certain characteristic sound when it's at its proper speed, feed rate, etc. In fact, different metals will have different sound.
 
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