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Music: to your ears, it's just another kind of noise.

It's 1630, and a hard day at work finally has ended. You're off to the parking lot to get your car and crank up the CD player. Soon, you're rockin', hip-hoppin', or rappin' your way down the highway, but at what cost? Ringing in the ears (also known as tinnitus) or permanent hearing loss (by degrees) can happen off the job, as well as on.

Have you ever had dinner in a restaurant where the noise was so loud you had trouble having a conversation across the table? Remember the 3-foot rule? You likely should have been wearing earplugs, just as you would have done had you been on the job.

When you're cutting the grass, hunting, or watching a NASCAR race from the grandstand, there may not be anyone around saying, "You really should be wearing earmuffs." That's why it's so important for you to recognize when you're at risk and to do whatever it takes to protect yourself.

You rarely notice your sensitivity to sounds diminishing because it usually happens ever so slowly. Then, one day, the realization hits home when a friend or your significant other yells, "How about turning down that TV? Are you deaf?"

Mobile Deafness Chambers

Car-stereo installations, like the ones in the accompanying photos, clearly are over the top in terms of power capacity and proximity of the speakers to vehicle occupants. The units most people listen to hopefully are more realistic. However, it's not uncommon for such systems to produce sound-pressure levels far exceeding the same limits for workplace noise--even as much as 100, 120 or 130 dB peak or more.

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No music is worth the damage that occurs to your ears when exposed to those levels for extended listening sessions. Regardless of the source, if you experience actual pain, tingling or ringing in the ears, or if you notice a slightly muffled sound sensation after listening to music, you likely have been overexposed.

It's a fact of life that hearing ability usually declines with age. However, it's abnormal for young people in their teens, 20s or 30s to experience permanent shifts in hearing. The means to prevent that loss is under your control.

Portable MP3 or Other Music Players

The growing popularity of portable CD and MP3 players has caused sales of these electronic devices to skyrocket in recent years. What's lacking is research to determine the effects of this increased usage. In other words, no one really knows if we're creating a whole future generation of hearing-impaired. Do we really want to wait to find out the answer?

What We Know

A variety of portable music players, as well as several different styles of portable headphones and inserts, is available today, each with its own set of characteristics.

Nine different portable digital players, coupled with 20 different headphone or earbud-insert combinations, were tested in a 2006 Canadian study (Keith, SE, Michaud, DS and Chiu, V; Journal Acoustical Soc of America, 2008 Jun; 123(6): 4227-37). This study gauged the maximum sound output of each setup. Output levels ranged from 101 to 107 dBA at the maximum volume setting. Estimates of actual listener sound levels could range from 79 to 125 dBA, depending on a number of factors. Among these factors are the recording level of the music; headphone type, fit and earphone seal on the ear; player-output voltage; and earphone sensitivity.

A similar study of portable players by a number of different manufacturers, using different styles of headphones--insert type, supra-aural (rests on the ears), and circumaural (completely covers the ears)-found maximum sound levels from 91 to 121 dBA (Fligor, BJ and Cox, LC; Ear and Hearing, 2004 Dec; 25(6): 513-27). When compared to the NIOSH-recommended standards for occupational noise, a maximum noise dose would be reached within one hour of listening, with the volume set at 70 percent of the maximum! The insert (earbud) style headphones produced higher sound output (7 to 9 dB) when compared to the stock headphones provided by the manufacturer, possibly due to direct insertion in the ear canal and a tighter ear seal.

Types of Headphones

Here's what is available today:

* Stock portable and insert type. These earphones insert into the outer ear; they don't tend to reduce distracting outside noise and are best when used in low-noise environments.

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* Earbuds and "isolating type. These mini, bullet-shaped earphones insert into the ear canals and provide a tighter seal. While testing indicates these devices may be capable of generating higher sound output than other types, they tend to reduce unwanted ambient noise to some degree. As a result, wearers may be less inclined to crank up the volume.

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* Supra-aural headphones. These devices rest on top of the outer ear and may be open-air or closed-style muffs.

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* Circumaural headphones. These earmuff-style headphones completely cover the entire ear. Such closed-type devices may tend to limit outside noise.

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* Active noise reduction (ANR) headphones. ANR technology aims to counteract high noise levels in the environment by electronically canceling out the noise with sound waves that are 180 degrees out of phase. By reducing competing noise, these headphones may reduce the tendency to increase volume settings to overcome external noise distractions.

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Five popular MP3 players, with both stock and four other types of earphones, were tested, using five different musical genres, white noise, and pure tones. The results were similar for all five models and didn't vary greatly across all of the five musical genres (rock, R&B, country, dance, and top 40). Again, earbud-style earphones averaged 5.5 dB higher than the supra-aural headsets, regardless of the kind of player being tested. (Source: Portnuff CDF and Fligor, BJ; Paper presented at NIHL in Children Conference, Cincinnati, OH; 19 Oct 2006)

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As we've mentioned throughout this issue's focus section on hearing conservation, damage to your hearing occurs over time. It's dependent on the level of noise that reaches your ears. So, minimizing the chance of hearing impairment can be achieved by reducing the volume of sound or limiting the time that you are exposed.

What We Don't Know

There are no current U.S. standards that regulate the sound output from portable music players.

In June 2008, the American Medical Association reviewed the available data and decided to maintain the focus of its recommendations on public education, rather than push for a campaign on restrictions. This focus was chosen for several reasons:

* The potential for damage to hearing is not dependent solely on the output of the devices but also on the length of listening time.

* There is very limited research evidence that defines the extent of the effect that such overexposures are having.

* As battery technology has improved, players are in use for more extended periods of time than ever before.

* There is great variability in the types and output of the many PMPs (portable media players).

* The recording level of the music being played differs from different sources.

* Personal listening preferences are a major factor in determining the potential risk.

What You Can Do To Protect Your Hearing

It's easy to see from this discussion that the risk of

hearing damage is very real, even from sources that we consider pleasure or leisure activities. Hearing loss and tinnitus are not conditions limited to older people. It can happen to you.

Be aware of noise present in your environment, and take actions to lessen your exposure (e.g., moving to a seat away from speakers in a noisy club).

Enjoy your personal music players, but set the volume at a reasonable level.

Limit the total time you're exposed.

When hazardous noise cannot be avoided (e.g., when operating power tools, mechanical equipment, or noisy recreational equipment), wear protective earplugs or earmuffs.

Protect yourself under all circumstances. You'll appreciate the effort later.

By Chuck Almond, Naval Safety Center
Table 1. Maximum listening time per day using NIOSH damage-risk
criteria. These listening times are the result of testing the
output of specific music players and headphone combinations and
are provided for information only. It is important to note that
your electronic device may vary.

% of Maximum listening time per day
Volume
Control Earbud Isolator Supra-Aural Stock Earphones

10-50% No limit No limit No limit No limit
60% No limit 14 hours No limit 18 hours
70% 6 hours 3.4 hours 20 hours 4.6 hours
80% 1.5 hours 50 minutes 4.9 hours 1.2 hours
90% 22 minutes 12 minutes 1.2 hours 18 minutes
100% 5 minutes 3 minutes 18 minutes 5 minutes
COPYRIGHT 2008 U.S. Naval Safety Center
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2008 Gale, Cengage Learning. All rights reserved.

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Author:Almond, Chuck
Publication:Sea&Shore
Date:Dec 22, 2008
Words:1431
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