Pro-Ears hearing protection deal for TBN members

DVerbarg · Apr 18, 2002

Mike,

When you get them be sure to give us a review. Am very interested in what a blue CUT owner thinks.

patrickg · Apr 19, 2002

MChalkley, What about active noise cancellation? Headsets with either compression or clipping, at best can only reduce the sounds by the dB performance of the non-electronic portion of the ear cups. There are a couple different benefits that you seem to want: 1. considerable reduction of loud sounds, and 2. some transmission or even amplification of quiet sounds. A has been stated, the clipping type circuits are better suited for impulse sounds like gunfire and the compression type sound more natural with no "discontinuities in the gain curve.

Neither of these reduce lound sounds any better than plain, non-electronic, muffs. You can get a reduction factor of 36 from muffs and plugs with on-line ordering for $18.95 (OSHA approved). Since the noise reduction factor is in dB and dB is a log function, 10 dB difference is a 100 to 1 reduction. Muffs rated at 36 only pass 1% of the noise that muffs rated at 26 will pass. Stated another way the 36 muffs are 100 times quieter than muffs rated at 26.

Muffs with active noise cancellation circuitry (totally diferent electronic approach from either clipping or compression) can always out perform the other two technologies or plain muffs.

Noise causes more bad effects than just hearing problems. Among others, it causes fatigue. Rutan and Yeager used active noise cancellation earphones while flying around the world non-stop without refueling. These units are of interest to pilots and should be to tractor pilots for many of the same reasons. There are no technical difficulties in listening to music, two way radio or other sound source (electronic analog signal) with noise cancelling earphones.

The noise cancellation problem with tractors is similar to that with aircraft. That said, here is a URL for "A Tutorial on Active Noise Reduction" http://www.avweb.com/sponsors/litspeed/anr101.html It is intended for the general aviation segment (private pilots) but is applicable to tractors as well. There is also a good section on the NRR ratings of non electronic headsets.

A statement on the site listed above, "passive hearing protection is very effective where there is less noise, or where the noise is predominantly at higher frequencies. It's just not the ideal solution for an aircraft noise environment.
I would strongly recommend considering ANR (Active Noise Reduction)." Aircraft noise for propellor driven piston enginen powered aircraft is quite strong in the lower frequencies as is tractors. Consider my Kubota L4610 with 4cylinder 4 cycle engine. At PTO RPM I'm turning say 2600 RPM. That is 1300 firings per minute or about 22 firings per second. This gives a strong acoustic peak at 22 Hz and its first few harmonics at 44Hz, 66Hz, 88Hz. I submit that tractor noise spectra are essentially similar to general aviation aircraft (less the slip stream noise of rushing air) so using noise control solutions developed for those aircraft is reasonable for tractors. The NRR ratings for regular noise control products are a weighted average general indicator sort of thing more suitable for noise fields with a lot of impulse sounds and lots of higher frequency components. In tractors the low sounds are stronger than the high frequency contributions. NRR ratings are misleading but in general more is better.

Hope this helps someone. I don't have a stake in this I don't sell an ANR product or have stock in anyone who does. Just bringing out some information that may be of interest.

Patrick

Patrick

Rick Jay · Apr 19, 2002

Patrick,

Thanks for your input and link to the ANR tutorial. I read the first bit of it, I'll have to return and get the rest later.

I do have a question though. Wouldn't the active noise reduction of most systems try to suppress ALL outside noise (sound), including desireable conversation or those "pesky" little sounds that might be an indication of a potential problem?

For instance, Bose sells a set of active noise cancellation headphones for home use ($299), but my understanding of their operation is to reduce all outside noise to better enhance "the listening experience". (I believe their product might be great for indoor use, but their maintenance instructions for keeping the headphones clean is contrary to the environment most of us would subject them to outdoors working with power equipment, so they might not be a good first choice for our applications here.)

Also, although I generally like Bose products, finding the technical specs for them is often difficult. Their marketing seems to be geared to the non-technical mindset.

~Rick

fishman · Apr 19, 2002

O.K. I got the box my Remington R2000 muffs came in, as well as the instructions. The instructions are very rudimentary, and consist pretty much of care instructions, directions on how to insert the batteries, and some promotional materials. There is no warranty information of any kind.

The box actually has a lot more information. Here are some quotes of interest:

"Two recessed microphones provide total reliability and stereo sound."

"Advanced, super-responsive AGC circuit limits high noise levels such as gunfire to 84 dB at the ear."
<font color=red>I don't know what an AGC circuit is.</font color=red>

"No cut out of normal speech - only high noise levels are reduced. Hearing is actually enhanced at low noise levels."
<font color=red> This seems to support my previous statement that these muffs use compression technology instead of clipping</font color=red>

The box goes on to say that the muffs weigh 9 ounces, each ear has independent volume controls, and the N-type batteries provide about 200 hours of use before needing replaced.

The box also gives the address for Remington, and provides a phone number (1-800-742-7053) and link <A target="_blank" HREF=http://remington.com>http://remington.com</A> for more information.

The biggest problem with the information is that no NRR is given. Since my daughter and I mainly use them for hunting, where I rarely used hearing protection before, I figured that some noise reduction was better than none. Strictly from casual observations between the Pro-ears and the Remingtons with the sound amplification off, I can't tell that one blocks more noise than the other.

Bottom line . . . If you have the money the Pro-ears is probably the way to go, since there is a lot more information available, as well as an excellent warranty. However, if you don't want to spend that kind of money, I've found the Remington R2000 muffs to be an acceptable alternative.

Rick Jay · Apr 19, 2002

fishman,

I'm not an expert on noise cancellation technology, but AGC stands for Automatic Gain Control. It is an amplifier that adjusts its gain based upon the level of the input signal.

Low volume signals get more amplification than High volume signals. It's been used in radio circuits "forever" to keep the audio radio signal at a near constant level even if the signal strength at the antenna varies.

Hope this helps.

~Rick

patrickg · Apr 19, 2002

Rick, Your remarks are valid and perceptive. If one wishes to hear all the possible "little (or not so little) noises" you can't throw any of them away, can you? I would rather not go deaf while trying not to miss some sound of interest masked by hearing damaging noise.

Lets make some reasonable assumptions and delineate some initial conditions to sort of get us on the same sheet of music. Lets assume for discussion sake that my characterization of tractor noise being similar to piston driven general aviation aircraft noise is "close enough." Lets also remember that most muffs (non electronic and no diaphrams ala "Lee Sonics" shooters ear plugs) are rated with a sort of average NRR figure. Most muffs are designed to (or just end up) working better on higher frequency noise and don't do so well below a few hundred Hz. Aircraft AND tractor noise has dangerous levels of low frequency noise that is not well supressed by most muffs. Things sound quieter with muffs on of course but that doesn't mean that there isn't still ear damaging low freq content still getting through.

If we were to wear good ANR muffs our hearing would be much better protected than wearing regular muffs or muffs with either of two other electronic technologies, clipping or compression. It is important to note that neither the clipping type nor the compression type use their electronic circuitry to reduce the sound/noise getting into the muff. They do not stop noise any better operating normally than they do with the batteries removed. The clipping and compression types use their electronics to selectively admit some more sound that would otherwise be elliminated (the reason you wear them in the first place). ANR is only going to improve muff performance appreciably in the low freq domain where much of the danger lies for our hearing that is not adequately handled by regular muffs. Some are user variable in their ANR circuitry so if it gets too quiet for you, you can reduce the cancellation.

The chief motivation for wearing muffs is to stop sound from harming your hearing andto reduce operator fatigue. If you use a 2 way radio from your tractor or want to listen to music (or get weather reports or stock market info) those activities will be markedly enhanced.

If there were specific frequency bands containing "information" of interest to you then a user variable amount of that could be injected into the ANR headset. Most (would you believe many?) ANR headsets are intended to be used to listen to a radio or music source AND frequently have a noise cancelling boom mike affixed as standard equipment to allow you to transmit with a better signal to noise ratio.

Again, my motivation is to preserve my hearing and reduce operator fatigue and a distant third is to allow 2way radio use, weather radio use, or music listening. I could always stop the tractor to talk on the radio or get the weather if I need to do that but an ANR headset would remove the need to shut down. Some models of ANR headsets are cell phone compatible so yo cold take/make a call while tractoring (or in my case roaring down the south Canadian river bed in a VW dune buggy). I don't think hearing all the sounds of the tractor experience to avoid missing some nuance which might indicate some mechanical malfeasance is worth loss or significant (over time) reduction of my hearing. In pure economic terms there is all that AMSLAN tutoring, lip reading training, hearing aid expenses...

I would be leary of any ANR equipment designed for HI-FI uses as they may not attenuate the high freq noise nearly as well as reqular muffs. Since most folks don't run tractors, aircraft, or jackhammers in their living rooms it may not have been a big issue.

I justify the somewhat large expense as MY EARS ARE WORTH IT and I can use the muffs tractoring, as well as around other noisy things like my new chipper whach shipped today. If I should trip and fall over a sack of money and start flying private aircraft more regularly, ANR muffs will be great.

Hope this gave some useful information and that any slight attempt at humor will be be appreciated, ignored, or at least go unpunished.

Patrick

DVerbarg · Apr 19, 2002

Patrick,

Your points are great. I would love to have an ANR headset. I believe ANR headsets address all the issues except one: workarea safety for others. There is a cool factor of being able to hear and find a leak in the exhaust system but more importantly is the ability to hear others who might walk up behind you. Of course they aren't supposed to do that, but my kids occassionally do things they shouldn't /w3tcompact/icons/shocked.gif.

It would be great if the ANR headset would allow the passive NRR (they do), ANR or DNR (they do at least one of these) and allow the voice sound range to be delivered back in at a controlled level (they don't, do they). This last factor I have not been able to find.

Can I hear voices behind me today? To a very small degree, yes. I don't want to loose what little ability I have to protect others around me in an effort to protect my ears but would rather have a politically correct "win-win" situation where my ears are protected and the ability to hear others is enhanced.

Do you know of specific ANR headsetst that might allow this?

patrickg · Apr 19, 2002

DVerbarg, What freq bands do you think contain the aural information you don't want to miss? ANR reduces potentially harmful low freq sounds. High freq sounds are attenuated by the passive component (muff). Most children's voices are pretty high freq in comparison to the band attenuated significantly by ANR.

Brief humorous aside: I had an idea for an imaginary product. A stethoscope type headset similar to the non electronic headsets on commercial airplanes. Motorcycle riders would plug it into their exhaust system so they could hear their exhaust as loud as they please while complying with NEW STRINGENT noise abatement regulations with stiff jail time penalties. Win win situation, they can blow their brains out with noise but not disturb anyone else. I know, I know, big brother can't allow anyone to harm only themselves without sharing it with the population in general.

Seriously, if you want to check your exhaust system from manifold to tailpipe as a regular part of preventative maintanance, it doesn't involve our discussion. Just use a mechanic's stethoscope or a rubber hose.

If you have to be able to hear every nuance of sound while operating your tractor, you are going to fail eventually because the extended periods of exposure to damaging sound will eventually make ANR a mute (deaf?) issue. As your hearing deteriorates you will lose the ability to hear those nuances of "funny noises" or your children playing.

The trick is to find a means of discriminating between sound you want to hear (signal) and sound you don't want to hear (noise). If you could pick a small number of freq bands that would contain the sounds of interest they could easily be captured by a broadband michrophone and passed through a set of audio filters (like a multi channel equalizer) and injected into the signal path of the ANR just like listening to music or an air traffic controller. This sort of circuitry has been miniaturized and is in some inside the ear hearing aids. It could be cobbled together by any fairly competent home electronics hobiest/experimenter for a few bucks and would be lighter than a brick and much smaller than a breadbox.

Except for the basic idea in the above paragraph, I can't think of how you could get close to what you ask for. Your two basic requirements: 1. reduce all potentially damaging/fatigue inducing sounds to safe levels but 2. let you hear the children at play, hear nuances of "funny noises", hear and dodge crickets mating in the grass (just kidding) are, I think, pretty much mutex (mutually exclusive). You see the problem is that you NEED to reduce the sound field's damaging components to a safe level without similarly reducing whatever sounds you don't want reduced.

Last suggestion, then I am at least temporarily out of ideas: There are several suppliers of after market ANR retrofit kits to put inside your muffs. Put a set inside a set of compression type muffs or better yet...

Get regular ANR muffs and have your electronics hobyist wire up a "companding" michrophone (CB radio types used to use companding mikes...similar to audio compression ) to feed audio signals into the music/ 2 way radio signal inputs. What does this do for you? You have ANR to reduce the "EVIL" pernicious low freqs, a good muff to attenuate the higher freqs and a variable compression/companding circuit to selectively, under user control, inject say 300-3000 Hz audio so you, under certain circumstances, can hear the kids. (When they are louder than the tractor.
You don't hear them now unless at least some freq component of their "noise" is significant with respect to the same freqs from the tractor OTHERWISE they are masked and not detected.

I lied, here is another idea but your wife and the Child Protective Services Officer might not be amused. Buy and install on your tractor, a "invisible fence" dog containment electronic system and have the kids wear the collars. First they get a beep to warn them to stay back from the tractor and if they get closer they get a mild uncomfortable negative reinforcement... Which due to your effective ANR muffs you will not hear any ensuing vocalizations. For a more graffic and intuitive explanation watch old StarTrek reruns with the "pain collar" on William Shatner/Capt. Kirk. I don't know what is more painful, his pain collar or his overacting.

Patrick

P.S. There is a lot of interest in detecting, classifying, and gathering information from weak sound sources in a high noise environment. It is the goal of sonar engineers. They use extremely powerful computers and a lot of other expensive gadgets that are too big for your tractor to carry in many instances.

DVerbarg · Apr 20, 2002

Patrick,

Without doing actual measurements on the voices of my wife and kids the range of sound that I would be interested in picking out and listening to would probably be in the 500-2000 Hz range. The human voice goes a little higher and in some deep voices a little lower.

Since I'm not in a position to spend much time tinkering and learning how to do this I may have to just get a headset and then tinker with it later.

The invisible dog containment fence idea - I'm afraid to ask my wife about that one. She would probably recommend that the system be changed so that the collar would go on me and I would get the shock /w3tcompact/icons/shocked.gif. I'm not even gonna ask....but it was a creative idea/w3tcompact/icons/crazy.gif.

Do you know good sources for ANR headsets that stand behind what they sell and offer competitive pricing? I've been "burnt" in the past buying photography equipment from mail-order/internet sources who had great prices but took my money and only delivered the goods after a couple months of haggling and threatening legal action. The lowest price is not always the best deal.