Noise levels of various milling machines

[pontiac428]

Don't worry about getting an ANSI Type 2 SLM, the phone apps are "close enough" as far as that goes for screening purposes. I've seen apps tested in sound labs, and they do fairly well considering the electronics and software handling the stream are totally uncontrolled. I'm not going to whine about a decibel or three at this point.

The latest science from ACGIH has been fully adopted by all DoD branches regarding hazardous noise. Any unprotected exposure over 85 dBA is hazardous as a steady state source. Impulse noise is hazardous at 92 dBA. Just like anything that comes in "doses," it's the dose that makes the poison. 85 dBA for 480 minutes is the line for wearing hearing protection and enrollment in a hearing conservation program. I'd be worried if my mill head under no load was over 80 dB. Most machines should be well below 80 without load, something is wrong at that point.

You cannot constructively equate varying noise to cutting operations, but the op is what makes the noise in a machine shop... so no-load running isn't a good indicator of noise exposure.

It's true that free field conditions are different than incident fields. It's not worth investigating- even if you had a magical wall that reflected 100% of the sound energy back at the origin, you would only change the noise level by the doubling rate, which is 3 dB.

The right way to evaluate hazardous noise is through personal dosimetry. Comparing no-load operator's notes is fun, but flawed.

 

[Iceberg86300]

Yeah, totally forgot to add that.

Any test plan would absolutely require test cuts & that would be a pain.

Would probably have to break it up like they do (did?) at Haas. All small machines run the same job in aluminum & then the bigger machines cut a test part in steel IIRC.

Figuring that out would likely be the most difficult part.

Sent from my SM-N975U using Tapatalk

 

[AllenV]

This has largely gone off the rails to where I regret bringing it up.

My hope and intent was to build a semi-quantitative informative list of informal noise measurements. Something better than anecdotes similar to “A is noisier than B” based on individual hearing perception of many hobby machinists in many very different workshop environments.

Certainly, a smart phone-based measurement with non-NIST-traceable hardware and software and uncontrolled environments is going to have significant standard deviation of error. But, over many, many data samples the aggregate results ought to be useful and informative.

What this is not, is a means to determine if any one machine is generating actionable hazardous noise.

 

[pontiac428]

This has largely gone off the rails to where I regret bringing it up.

My hope and intent was to build a semi-quantitative informative list of informal noise measurements. Something better than anecdotes similar to “A is noisier than B” based on individual hearing perception of many hobby machinists in many very different workshop environments.

Certainly, a smart phone-based measurement with non-NIST-traceable hardware and software and uncontrolled environments is going to have significant standard deviation of error. But, over many, many data samples the aggregate results ought to be useful and informative.

What this is not, is a means to determine if any one machine is generating actionable hazardous noise.

I don't think it went of the rails, Allen, I just think the post led to discussion rather than data gathering.

For many years, it has been my job to design and conduct noise evaluation studies within DoD. I also do sound mitigation engineering, comparison studies, and compliance studies for personal/industrial exposures and for public/environmental exposures.

I can probably help, but I tripped up on building a database of quantitative results of machinery under no-load conditions. That's akin to measuring noise from a truck at idle. Does no good, the noise comes from the highway, just as machining noise comes from the tool on the work first, the machine's clearances next, then power transmission, then bearings...

I think I took your thread a different direction based on what I saw as a flaw in the initial question. Re-reading it I guess it's clear that you just want to know how noisy everyone's head is. I can measure mine, but even with the RPC in the background I don't think I'm outside of 50 dB. Most sound level meters won't even integrate samples below the 65 dB criterion, so I can measure but won't be with high statistical confidence, because anything below 65 is extrapolated as it is outside the calibration curve.

 

[matthewsx]

Welcome to Hobby-Machinist.

We specialize on laying entirely new rails to places you never thought of going.

I too spent many years exposing myself to all kinds of noise. From being a sound engineer, to running around with racing cars and karts, and of course working on machines.

It was probably me that set you down this path with my noisy gear head comment on your prior post.

I for one have made it a practice to always wear hearing protection in the shop.

John

 

[Iceberg86300]

Yeah I wasn't thinking about safety at all LoL.

Just an engineer being a little too analytical.

My only aim was generating a good comparative data set by removing the controllable variables of the meter as well as user induced error by prescribing exactly where & how to hold it when taking X number of samples.

If one isn't going to play the traveling meter game I'd say the importance of adhering to a rigid set of instructions on positions, orientations, and even how one holds their phone, goes up exponentially. Which isn't to say it wouldn't be important if everyone had the same meter. It's just that if you allow the meter variable you want to be extra careful in minimizing the user variable.

Otherwise you could end up with something that's even worse than what you're trying to avoid.

i.e., now you have one guy that took a measurement of a naked desktop machine cutting air at 2 feet with the mic pointed straight at the loudest part of the machine fighting with another guy saying their cat50 monster with a 10 insert shell mill buried in steel is quieter b/c they took a measurement at 5 feet from an enclosure with a muffled microphone port b/c it's half covered by a thumb & pointed at themselves instead of the machine.

Basically anecdotes that are legitimized by numbers.

There's a thick layer of hyperbole applied to this example, but I hope it illustrates where I'm coming from.

Sent from my SM-N975U using Tapatalk

 

[matthewsx]

Yeah I wasn't thinking about safety at all LoL.

Just an engineer being a little too analytical.

My only aim was generating a good comparative data set by removing the controllable variables of the meter as well as user induced error by prescribing exactly where & how to hold it when taking X number of samples.

If one isn't going to play the traveling meter game I'd say the importance of adhering to a rigid set of instructions on positions, orientations, and even how one holds their phone, goes up exponentially. Which isn't to say it wouldn't be important if everyone had the same meter. It's just that if you allow the meter variable you want to be extra careful in minimizing the user variable.

Otherwise you could end up with something that's even worse than what you're trying to avoid.

i.e., now you have one guy that took a measurement of a naked desktop machine cutting air at 2 feet with the mic pointed straight at the loudest part of the machine fighting with another guy saying their cat50 monster with a 10 insert shell mill buried in steel is quieter b/c they took a measurement at 5 feet from an enclosure with a muffled microphone port b/c it's half covered by a thumb & pointed at themselves instead of the machine.

Basically anecdotes that are legitimized by numbers.

There's a thick layer of hyperbole applied to this example, but I hope it illustrates where I'm coming from.

Sent from my SM-N975U using Tapatalk

I think you have touched on something that might be of great value in our community.

We already do the pass around box but not any calibration standards as you’ve pointed out other folks do.

This would actually be awesome, we have some members who pursue precision to a very high standard. If they could create a set of calibration tools and instructions for checking our measuring tools that would be awesome.

Mods, what to you think? @DavidR8 @mmcmdl?

John

 

[DavidR8]

I love this idea @matthewsx

 

[AllenV]

My thinking was to ask for a measurement that is easy and take only a few moments to complete. So “cutting air”, as it was called, seemed the measurement that would garner the most participation. That test ought to pull out useful insight into the inherent noise of the drive train and motor. It might even reveal something about gear-type transmissions that have high-quality ground gears versus gears that have poor finish quality.

Seems to me that attempting to including cutting of metal brings in far too much job-specific data that needs to be known, controlled, and tracked. Things like type of metal, type of cutter, 2 or 4 flutes and is it sharp? Then you get into material removal rates. Is the machine doing a light pass? Or is it ripping away steel with blue chips? And how many folks are willing to calculate MRR or set up a condition to replicate a specific MRR? Do we ask for an operational set-up that is at the limits of the smallest benchtop but easy-peezy for a Wells-Index beast? Maybe someone’s gibs are a bit loose and that makes noise from table vibrations. These are all the complexities that led me to simply ask for “cutting air”.

If the test is quick and easy, then maybe we get hundreds of data points from the HM community. Perhaps over dozens of different machines. These data would then be amenable to statistical analysis to pull out the most likely noise level of a given model of mill. Doing that would require at least 3 examples of each mill. 5 or 6 would be better. If we only get one example of a few different machines then the exercise will have been futile.

I am seeing, in the posts above this one, some great creative thinking emerging as to how to do a much more accurate and precise measurement. The pass-around box might include a cutter and a piece of metal along with a noise meter. If noise meters are precious, maybe someone has an out-of-service iPhone that could be wiped and loaded with the NIOSH app. Looking forward to seeing how this evolves.

Of course, nothing says we can’t do quick and easy while pursuing a better measurement.

PS: Holy cow, I just looked on-line. A cheap noise meter is $20. Maybe one of you with experience in doing quality noise measurement could figure out what an acceptable meter would cost. If the goal is RELATIVE noise, not absolute, then a cheap meter might do fine.

 

[AllenV]

Welcome to Hobby-Machinist.

We specialize on laying entirely new rails to places you never thought of going.

I too spent many years exposing myself to all kinds of noise. From being a sound engineer, to running around with racing cars and karts, and of course working on machines.

It was probably me that set you down this path with my noisy gear head comment on your prior post.

I for one have made it a practice to always wear hearing protection in the shop.

John

You were just the 3rd or 4th person to point out that geared-heads are noisier. But the 1st after I had committed to upgrading my mill and put up that post over in PM-world.

I fully support wearing hearing protection, or any other needed PPE. However, my background is from a major US national laboratory. At that institution a heavy emphasis is placed on seeking engineering solutions to mitigate hazards. In other words, if an operation is hazardous, work to remove the hazard. This might be redesigning the operation to be fundamentally less hazardous or by installing fixed mitigations, such as guards. PPE comes in to practice after REASONABLE EFFORTS have been made to remove the hazard. For a little while my management offered a $500 bounty for new engineered solutions. That stopped shortly after he paid out the first $500.

In my little shop, that means I sought a low-noise, but fast, air compressor. And now I am interested in learning what are the reasonable trade-offs to refiguring my milling operation with some consideration of noise. The point is fast becoming moot for me, personally, as I am highly likely to buy a belt-drive electronically-variable-speed mill. But I remain very interested in this topic.

Of course, noise from the audio entertainment system is grandfathered in.