Pro-Ears hearing protection deal for TBN members

MChalkley · Apr 21, 2002

patrickg - ANR/ANC muffs have the theoretical potential to reduce all outside noise to dead quiet, which is quite a feat. However, for my purposes, and the purposes for which I reviewed them favorably for the TBN audience, that's not just useless, it's dangerous. I realize that they don't achieve complete negation of all ambient noise, and that they excel in certain frequencies, but that's of little value to me, either.

For example, while much of the engine noise and vibration may be very low frequency noise, the hydrostatic whine and other noises are pretty high. Besides, regardless of the specific performance characteristics of a particular brand and type of ANR/ANC muff, I don't want to rely on their design to allow me to hear safety-related noises. What frequency will they be? Who can say? A child screaming is certainly a high frequency, but sounds that may indicate impending mechanical failure that could certainly create a safety hazard may or may not be.

I think a far better approach is the sound compression method. You know you're hearing everything, and some things, things which are the most likely to be safety-related, can be heard better than with the naked ear. That's hard to beat.

As for the amount of noise reduction, I agree that ANC sets have the ability to perform better, as I said. But enough of most anything is enough. And the Pro-Ears provide more than enough noise reduction for my purposes, and I know from experience that my EF-500 is louder than most any CUT. Now, if you're running a jackhammer, you're probably going to want to use light ear plugs in conjunction with the Pro-Ears, or a different technology, like, perhaps, ANC. But, as I said, I didn't review them with jackhammer operators in mind, nor did I test them with one.

Don't get me wrong - I think ANC/ANR technology is great. I just don't think it's safe to use on or around equipment. And, for that reason, it's a very good thing that compression technology can provide all the noise reduction you need, while still allowing safe operation of the equipment.

MChalkley · Apr 21, 2002

fishman - Thanks for the additional info. I'm still trying to get more info on them, too. You sure can't argue with the price. The Wal-Marts around here don't have them, though, so I haven't been able to look at them, much less test them.

Rick Jay · Apr 21, 2002

Wow, you guys never cease to amaze me with all the diverse expertise on this board!

Once this semester is over and things settle down a bit, I'll probably pick up a set of the Pro-Mag Dimension 2's...unless something better comes out between now and then.

I'm also intrigued by the Bose units and might get a set for use around the house. With three "little ones" around the house, I have a different type of "noise" I sometimes have to contend with, and I'd be interested in seeing how effective they are. It would also serve to satisfy some of my curiousity with the technology of ANR.

~Rick

MarkC - Is a congratulations in order? I see you've been promoted to "Moderator" status. /w3tcompact/icons/smile.gif

patrickg · Apr 21, 2002

DVerbarg, Sorry for the delalyed response, is it "better late than never?" or "Better never than late?" My mouse died and I just got a new one installed. Terrific "plug 'n' play, out with the old and in with the new and it works.. Nice mouse, Logitech optical with scroll for $20. No moving parts in the x-y part just the buttons. Last one died in the horizontal axis.

Anyway, put the transmitters on the kids and the pain collar on you or at least defeat the shock and clip the collar/receiver on you or your tractor where you can hear it go off. Actually, there is no way to absolutely guarantee the safety of anyone near working machinery, period. OSHA etc. make things better, usually, but there has to be either discipline or exclusion from the work site.

Sad but true. If you run a tractor with kids anywhere around and expect to guarantee their safety then there must be either some exclusion at work or a lot of discipline (and I don't mean after the fact punishment) or both. It is like kids and guns. If parents abrogate (abdicate?) their responsibility then bad things happen and we all end up being forced to have trigger locks etc. I better rein in here and now before I stir up a hornet's nest regarding personal responsibility along the lines of the thread, "prosecute the parents."

Regarding ANR. While a physics undergrad many decades ago (about 1970) in an upper division acoustics class I asked the prof why we couldn't put little michrophones in front of small planar styrofoam speakers (they had just come on the market) and sense the acoustic pressure wave just in front of the speaker and adjust the speakers output to be equal in amplitude and opposite in phase to cancel the incident far field sound. I thought it was a reasonable subject for research (being an experimentalist/empiricist about 75-80% and theoretician 20-25%). Well, he ridiculed me in no uncertain terms poo pooing the idea as worthless and having plenty of other things to pursue and his being a tenured prof and I a lowly undergrad, I didn't have much recourse. My garage was full at the time with reloading equipment and my home brew 6000 watt tunable to different colors, pulse LASER so I let it go. Not the first idea I ever had that later turned up with commercial application. No sour grapes here, I'm pleased as punch someone, albeit quite a while later, did something about it.

That might explain my interest in the technology. Being a realist, I just want what works and am in a position to understand the technology, perhaps a bit more easily that the next guy in line at Burger King. I am still researching but am narrowing down the field toward a mid priced unit with a high NRR (26) and good active cancellation in the lower freqs plus a michrophone so I can use it for comms as well. These things aren't cheap but I am leaning toward a factory ready unit rather than retrofiting available ANR units into existing muffs. Even doing the install myself rather than paying $50 or so I would still rather buy an integrated unit, even if it is a few bucks more.

I'll post my choice when I finalize it.

Here is a good unit specs wise but pricey.

Vweb Review of the Lightspeed 25XL HeadsetClick to view.

Lightspeed Headset 25XL

The deepest and broadest low frequency cancellation of any Lightspeed
unit: 25-28dB of active cancellation and 22dB of passive cancellation.
Auto Shut-off - the ANR turns itself off if you forget to turn it off.
Weighs under 16 ounces.
ANR powered for more than 50 hours on just two AA batteries.
Independent left and right ear volume controls.
Stereo-or-mono switchable.
Two sets of 1-1/2" thick temperature-sensitive Confor-Foam ear seals -- Soft and
Ultrasoft.
Headset bag included.
Press Review: "The company says the 25XL will be "the most comfortable
headset you've ever owned," and in this case the marketing hype may be true....All
headsets must fit snugly to provide passive noise reduction, but the 25XL didn't
exhibit any sense of clamping."-- AOPA Pilot
Click link for more details.

Lightspeed Headset 25XL 25XLOffline Price: $599.00 Online Price: $585.00

Go to this URL and look at the model QFR-CC for $275 (ordered on-line) High passive NRR of 28.7 plus 12-15 ANR in the lower freqs.

Not nearly as much ANR but respectable and a great passive NRR for $310 less.

http://store.yahoo.com/avshop/lightspeed-qfr-xc-headset.html

Hmmmmm, I gotta try to get some noise specs on tractors (Preferably power spectra but I'll take what I can get.), anybody been there, done that, or know where the results might be available?

Patrick

patrickg · Apr 21, 2002

MChalkley, In theory, everyone on TBN might be struck dead by lightening wihile reading this post but it is highly unlikely. I have been looking, and looking fairly hard at what is on the market. I have seen no commercially available ANR product that remotely approaches perfection. You still hear noise, just less, especially low freq noise.

A small correction/clarification: The sound compression method IS NOT A NOISE REDUCTION TECHNOLOGY. All the noise reduction is achieved by the muffs. Sounds, after being attenuated by whatever "frequency dependent attenuation curve" is provided passively by the muffs are then reintroduced into the muffs selectively in a compresesed fashion, i.e. with reduced dynamic range.

There, that said, I don't have an axe to grind, and do not wish to cheer no matter whose ox is being gored. If the compression technology muffs work for you, that's great. If that is the technology I wanted, I would already be using it ala the home brew method since the technology is much much simpler and can be easily retrofitted to existing muffs for a lot less bucks that the off-the-shelf solution.

If someone has led you to believe that ANR will be, in the words of Simon and Garfunkle, "the sound of silence" then you have been mislead or worse.

I still have strong reservations that you can simultaneously reduce the SPL (Sound Pressure Level) to a safe exposure intensity AND hear the kids or whatever. The tractor is louder than the kids or just about most things you might want to hear. The compression technololgy does not selectively reduce one sound over another. There is only so many electronic techiques available to the designers. I don't pretend to know all the tricks the designers may employ to get the job done but I know what the job is and shall we say the laws of physics (which they can't break).

Wearing the compression muffs while the tractor is working there will be a certain time averaged volume level used as feedback to a voltage controlled amplifier (or equivalent circuitry) that takes a sliding window average of the ambient sound and adjusts the gain/attenuation of the muffs audio circuits. This means that when the average ambient sound level is high/loud the gain is reduced when the ambient is not so loud it is reduced but not as much as before. They may even amplify real weak sounds (a plus for your purposes if you're wearing the muffs and the tractor is switched off) This levels out the sound like the "EMERSON" audio device you can use with your TV to keep commercials from blaring (retail, about $50)

I'll cut to the chase... However much the compression technology reduces the incoming sound of the tractor it reduces the "sounds of interest like children and funny-little-something-going-wrong sounds by the same ratio. You do NOT get an improvement in signal to noise ratio. If you can't hear the kids well enough over the sound of your working tractor NOW you still won't while wearing the compression type muffs BUT you will have more aural comfort and less fatigue while not hearing the kids any better.

I'm not sure, maybe you'll have to give us a user report on, if the ability to amplify weak sounds so as to reduce the "isolation" effect of wearing muffs when the ambient noise is fairly low (not on a hard working tractor) is of value in actual practice. This would be when say you shut the tractor off or dismount temporarily walking away from it so it isn't so noisy. In this case, amplification would allow you to hear someone or something you couldn't with regular muffs or ANR muffs.

In closing (thought we'd never get here?) there could be some benefits to good muffs with compression technology. If I were to find a set of muffs in a box of Cracker Jack I would want them to have both user adjustable compression technology and ANR. Since that isn't happening and I don't feel competent to home brew ANR and I personally don't want ONLY compression technology then I am reduced to buying ANR. I could fairly easily add compression technology to ANR muffs, that is a much easier problem.

Given that it seems we are persuing different requirements, it is not unreasonable in the least that we should approach different solultions.

Patrick

MChalkley · Apr 22, 2002

Patrick - The sound compression method IS NOT A NOISE REDUCTION TECHNOLOGY. I dunno. Here's my take on it, though: I define noise, for purposes of this discussion, to be any sound that's loud enough to hurt, cause fatigue, and/or mask important sounds I do want to hear. With the sound compression muffs, the noise is not loud enough to hurt, doesn't cause fatigue, and doesn't mask sounds that I want to hear, therefore it is reduced. Does the technology not meet some engineer's definition of "noise reduction"? Like I said, I dunno. I don't care, either. In very practical terms, it reduces noise for me. So no matter what anybody else calls it, it's gonna stay "noise reduction" to me - I'm describing the effect they have, not using a technical term. /w3tcompact/icons/smile.gif

If someone has led you to believe that ANR will be, in the words of Simon and Garfunkle, "the sound of silence" then you have been mislead or worse.
 I didn't say it had been achieved in real-world applications, just that it was theoretically possible. Still useless to us practical types, but theoretically possible...

I still have strong reservations that you can simultaneously reduce the SPL (Sound Pressure Level) to a safe exposure intensity AND hear the kids or whatever. The tractor is louder than the kids or just about most things you might want to hear. The compression technololgy does not selectively reduce one sound over another. Once again, discussions on the theory here, the circuit design possibilities, technologies in existence, etc. are all wasted on me. I don't know, and really, really don't care. I'm a tractor/equipment nut, not an ear muff nut. There could be two tiny beer cans with a string between them inside the cups, for all I care. I don't know how they work, other than the fact that I do understand the principle of dynamic range, and sound compression, from a practical standpoint, and from a somewhat technical standpoint (I've also been a shortwave radio nut for 20 years or so), but I do know they work. However, while the compression technology doesn't selectively reduce one sound over another, it does reduce the loud ones, and amplify the soft ones (if you enable that feature). And that, in practice, does enable you to hear soft sounds that would otherwise be masked by the very loud ones. It may not be possible from a theoretical standpoint, but it sure works in practice. (And this may be the first time that something theoretically impossible has been achieved. I knew the guys who designed these things were good, but I had no idea they were that good.)

I'll cut to the chase... However much the compression technology reduces the incoming sound of the tractor it reduces the "sounds of interest like children and funny-little-something-going-wrong sounds by the same ratio. No, no, no. What you say is true if the sounds in your example start out at the same decibel level, otherwise, that's not remotely close to what really happens. Loud sounds get compressed, soft ones get amplified (if you want them to be). The overall dynamic range of the sound you hear is compressed. All I know for sure is, it works. I hope it's theoretically impossible - as I said, I'm all for having discovered something that can't happen. Maybe I've got the only ears in the world they work with - that's ok with me, too. Except that poor Mike and Charlie will have wasted their money. And I really appreciate the guys at Ridgeline going to all that trouble to design something that only works for me. /w3tcompact/icons/wink.gif

MChalkley · Apr 22, 2002

Rick - Just remember that, unless you're planning to use them with a radio, you can get the Dimension 1 model and save yourself some money.

Starting tomorrow (actually later today, at this point), I'm going to be using them pretty much all day every day for a week, so I'll let you know how they worked on an extended basis.

I've been curious about ANR for some time, too. There's no doubt that there are applications where it should be much better than sound compression technology, but I don't think operating machinery is one of them.

patrickg · Apr 22, 2002

MChalkley, OK, OK, I'm sorry, I apologize for being so slow. Now I get it, your mind is made up, I'll quit trying to confuse you with facts. (almost)

But as "Detective Columbo" would say, there is just one more thing...

I gave this part a shot before but failed miserably to get the idea across. Sometimes I'm a real bad explainer...
The compression technology muffs can't, as I think you have come to believe, simultaneously amplify weak sounds while cutting down on strong sounds. At any given moment in time they are doing pretty much the same thing to all the sounds. If you are in a high noise environment so that the circuitry is "holding back" it is holding back weak sounds by the same ratio, making weak sounds weaker by the same ratio as it is reducing strong sounds.

Since you are a short wave guy (I got my first ham radio lisc in 1962) you should be familiar with AVC and AGC and the meaning and effect of fast atack and slow decay circuits for same. I'd bet dollars to doughnuts that is pretty much how their compression muffs work.

Suppose tha you are tuning around with your shortwave receiver and there are two AM (double sideband) sations on the same frequency. The problem is then how to hear the weak station in the presence of the strong station. For this analogy we have to assume a non directional antenna. The rcvr's AGC circuit sets IF gain dependant on received signal amplitude and doesn't know, care, or have the ability to tell from which station. The strongly received station will cause the AGC circuit to reduce IF strip gain to within design optimum envelope levels. In so doing the contribution from the weak station is reduced by the same ratio and it is heard even less. As for this analogy the stations are on the same frequency we have no controls on our radio that can boost the weak station without proportionately boosting the strong station and perhaps going into non-linearity, a bad thing that introduces distortion and reduces intelligibility.

Similarly all the sounds coming into the compression muffs are boosted or cut back by the same ratio at any given time. The only time "weak sounds are amplified" is when there are NO strong ones present which is likely not the case when you are working your tractor or you wouldn't be looking for any kind of noise reduction solution.

Q.E.D.

Patrick

PaulT · Apr 22, 2002

I don't know much about electronics from a theoretical standpoint, so I'll have to stick to the practical standpoint/w3tcompact/icons/smile.gif

Patrick, I don't see in any of your posts that you have ever actually tried a pair of these things on, other than the ANR type devices, regardless of brand, in a tractoring/construction/farming environment. Practically speaking, you have no experience with what these things can do for your hearing while operating a tractor. If you do, I'm sure we all would be curious to hear of your opinion about how they performed for you.

Again, practically speaking, I could imagine (though I wouldn't know how, or what acronyms to use to make a bill of materials for the device) that someone could make a device that amplifies a relatively quiet sudden noise selectively over a relatively lound constant noise by determining the incremental dB level if it were in a different frequency range from the constant noise. I think the frequency differentiation is an important part of how these work (just guessing). If I am guessing correctly, then you 2 AM station analogy is moot (not mute OR deaf)/w3tcompact/icons/wink.gif.

Anyway, a short note on the theory of these things was interesting reading. A long diatribe on someone's misunderstanding of the theory wasn't. I hope that people will continue to buy neat products and post the practical results for us to read about. I also hope that we won't hammer them over the lack of theoretical accuracy their opinions represented/w3tcompact/icons/blush.gif

dmccarty · Apr 22, 2002

Mr. Moderator,

Sorry I could not resist! /w3tcompact/icons/smile.gif

Have you used the Pro Ears with a rotary cutter? Or anything else at RPM
speeds?

I'm thinking about getting the Pro Ears for a couple of reasons besides
protecting my hearing.

Right now I cannot hear anyone in a car if they pull up behind me. Would
you be able to hear someone drive up from behind you?

Did you get the Pro Ears Dimension 2 and have you tried to listen to the
radio while running the tractor? That would be a biggy for me but I'm
wondering about reception but that is another concern. Guess I might
have to mount an whip antenna! /w3tcompact/icons/smile.gif

Thanks,
Dan McCarty