Sunday - June 21, 2009

What? What? Speak Up Please!

Hmm, that is a good question. While a good snarky answer could be “the ones that you’ll wear - good fit is everything”, purchasing first class hearing protection demands a bit of research.

First, let’s clear the air: guns are loud. Really loud. Somewhere in the vicinity of 140-165dB. Loud enough to cause you permanent total hearing loss. But they aren’t loud all the time. The typical bark from the muzzle only lasts a couple of milliseconds; a whole day’s worth of shooting at the range might expose you to 3 or 4 seconds of total noise. But it’s percussive noise. Gunblast can figuratively hammer the air right out of your lungs; what do you think it’s doing to your eardrums? Hearing protection is a must.

Next, let’s look at the actual sound of gunfire. It’s mostly low frequency. BOOM. 40-70hz. And most hearing protection is only rated down to 125Hz, and almost all hearing protectors offer much less protection at the lowest frequencies.

I looked around the internets, and I learned a few things. Most, if not all, of the earmuff companies feel you should wear a double layer of protection: earplugs and earmuffs. You betcha, that makes sense. Yet nobody does this. I started shooting back in the days when nobody wore hearing protection at all. It wasn’t such an issue at the indoor range with everyone popping away with their little .22 rifles. Until that psycho in the last lane opened up with a .357 Magnum. Horry Clap those are loud! In the early 80s I had, and still have, a pair of David Clark 10a muffs, the standard muffs everyone has. They seem to do an Ok job, but really ... they aren’t so great:
Hz        dB      SD    Net Expected Attenuation
125       10.9    1.4     9.5
250       20.9    2.4    18.5
500       28.8    3.6    25.2
1000     32.8    2.6    30.2
2000     35.9    1.4    34.5
3150     37.4    2.3    35.1
4000     38.3    1.6    36.7
6300     37.5    2.1    35.4
8000     37.1    2.7    34.4
NPR Rating: 23dB



Years later I found the Peltor Bullseye Ultimate 10 earmuffs, and they were much, much better. These muffs have an NPR Rating of 29-30dB. I don’t have that model’s specs, and they may be discontinued. They changed the “crack” of the blast to a “thump”, and it seemed quieter too. Plus, they cost half what the Clark muffs cost. These work fine, but get knocked off my right ear when I shoot my high combed Weatherby rifle. So far they are the best I’ve tried, but there may be better earmuffs available. And the getting knocked off the ear thing is bad, which is why I’m looking for some earplugs as well.



Right now, the best model Peltor muffs that I can find are the Optime III and the Bulls Eye III, both of which far outperform the old Clark 10A muffs, and ought to get an NPR Rating of 34-35dB. Except that 30dB is the top rating, because the ANSI law is from 1974! [update: no, I am wrong. The new standard is ANSI S12.6-1997.
Hz        dB      SD    Net Expected Attenuation
125       17.4    2.1    15.3
250       24.7    2.6    22.1
500       34.7    2.0    32.7
1000     41.4    2.1    39.3
2000     39.3    1.5    37.8
4000     47.5    4.5    43.0
8000     42.6    2.6    40

It’s obvious these are much better than the first set. They are probably quite a bit better than my 10 year old Ultimate 10s, but these may only be for sale in Britain, for around $30.



Here in the USA, the Howard Leight company makes the Bilsom Thunder T3:

Hz        dB      SD    Net Expected Attenuation
125       24.7    2.8    21.9
250       29.8    2.7    27.1
500       35.5    2.8    32.7
1000     38.5    3.0    35.5
2000     37.9    2.5    35.4
3150     39.6    3.1    36.5
4000     39.6    2.4    37.2
6300     41.9    2.6    39.3
8000     42.3    2.4    39.9
NPR Rating 30dB

Appropriately named, the Thunder T3 muffs seem tuned to better attenuate lower frequencies than the Ultime III muffs. And that seems just right for the rifle range. $20 at Amazon.

But we’re only halfway there. Like I wrote, gun fire is 140-165dB. The best of these muffs can take away about 22dB of that. Which means your ears are still getting 128dB or more. This is why you want earplugs as well.

Howard Leight MAX™ earplugs, about $1 per pair:

Hz        dB      SD    Net Expected Attenuation
125       40.9    3.5    37.4
250       43.0    3.9    39.1
500       44.8    3.8    41.0
1000     38.9    2.8    36.1
2000     37.2    2.7    34.5
3150     47.4    4.5    42.9
4000     48.5    3.1    45.4
6300     47.7    4.4    43.3
8000     47.8    3.9    43.9
NPR Rating 33dB

It’s pretty obvious that the best earplugs are far more effective than the best earmuffs. And many people choose to just wear the earplugs alone. Plus, they’re cheap, weigh nothing, and they fit in your pocket.

But for the best protection - and what real good is just a little protection? Do you want to be just a little deaf, like me? Trust me, this sucks every day of my life - you ought to wear both. Together they can reduce gun blast down nearly 60dB, down to 100dB or less. Which is still loud, but hardly damaging at all, especially when you’re exposed to about 3 seconds worth in a whole day of shooting.

PS - (you knew I was going to mention this) - we ought to have sound suppressors on our rifles, like they do in Europe. They aren’t “silencers”, not even close. But they can knock another 30dB off the blast. And it’s for your own ear’s good!! Hey Nanny State, help us out here! And while you’re at it, extend the frequency testing at both ends: 63Hz and 16,000Hz, to get the really low sounds and the really high ones.

UPDATE: Aww crap. The government says that doubling up doesn’t add much more than an extra 10dB in protection. Sure. That’s why I can’t hear a damn thing when wearing both, and gun blast is about as loud as two hands clapping.

A personal hearing protection device (or hearing protector) is any device designed to reduce the level of sound reaching the eardrum. Earmuffs, earplugs, and ear canal caps (also called semi-inserts) are the main types of hearing protectors. A wide range of hearing protectors exists within each of these categories. For example, earplugs may be subcategorized into foam, user-formable (such as silicon or spun mineral fiber), premolded, and custom-molded earplugs. In addition, some types of helmets (in particular, flight helmets worn in the military) also function as hearing protectors. Refer to Nixon and Berger [1991] for a detailed discussion of the uses, advantages, and disadvantages of each type of protector. Items not specifically designed to serve as hearing protectors (e.g., cigarette filters, cotton, and .38-caliber shells) should not be used in place of hearing protectors. Likewise, devices such as hearing aid earmolds, swim molds, and personal stereo earphones must never be considered as being hearing protective.

Ideally, the most effective way to prevent NIHL is to remove the hazardous noise from the workplace or to remove the worker from the hazardous noise. Hearing protectors should be used when engineering controls and work practices are not feasible for reducing noise exposures to safe levels. In some cases, hearing protectors are an interim solution to noise exposure. In other instances, hearing protectors may be the only feasible means of protecting the worker. When a worker’s time-weighted noise exposure exceeds 100 dBA, both earplugs and earmuffs should be worn. It is important to note that using such double protection will add only 5 to 10 dB of attenuation [Nixon and Berger 1991]. Given the real-world performance of hearing protectors [Berger et al. 1996], NIOSH cautions that even double protection is inadequate when TWA exposures exceed 105dBA.

Ok, what’s the difference between dB and dBA? dB is decibels, and dBA is “A” weighted decibels. It’s a filtering algorithm that tries to approximate human hearing sensitivity. Beyond that, I don’t understand it. But I do recall from the audiophile world that it takes a heck of lot more power to make a low frequency sound seem to be as loud as a higher frequency sound. So maybe less hearing protection at low frequencies is Ok, since we can’t hear those frequencies well to begin with? Oh, and TWA means “Time Weighted Average”, and I think the test time is 8 hours. Do we have any aural experts who can ‘splain this stuff better?

Posted by Drew458     on 06/21/2009 at 11:14 AM   
Filed Under: • Guns and Gun Control •  
• Comments (1) • Trackbacks(0)  Permalink •  

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