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Dangerous Decibels

The loud report of a weapon discharged next to an unprotected ear can deafen a tactical officer and give bad guys an advantage. But there's a simple solution to this problem that few entry teams use.

August 01, 2008  |  by Lawrence Heiskell, MD, FACEP, FAAFP

Suppressors are very affordable. Professional military and law enforcement suppressors can range from $750 and up.

Today's suppressors are smaller, lighter, and have a longer projected lifespan than their predecessors. One manufacturer is now producing suppressors that have a projected life span of more than 30,000 rounds.

Heckler & Koch and SIG Sauer produce handguns with factory threaded barrels ready for suppressor attachment. There are also several manufacturers that produce threaded barrels so that almost any handgun can be fitted with a suppressor. So most agencies will not have to spend a lot of money retrofitting their weapons to accept suppressors.

As for long guns, many law enforcement agencies are switching to the Colt M4 or some variant of the AR-15 carbine as their primary tactical team weapon. Several companies are producing suppressors for these weapons. SureFire makes a wide variety of suppressors for law enforcement and military applications. Long gone are the days of screwing on suppressors to these guns after removing the bird cage flash hider. Today's suppressors have quick attach/detach designs that allow the operator to attach and remove the suppressor from the weapon in a matter of seconds.

With the current climate of litigation and liability for workplace injuries, it makes good sense for law enforcement agencies to become proactive and take steps to mitigate increased disability payments and prevent the early retirement of tactical officers because of noise-induced hearing loss. The amount of money saved by city and county governments could easily be $15,000 to $30,000 per year for each officer who could be out on early retirement or disability from hearing loss.

The few dollars invested to retrofit the teams' weapons will pay huge dividends in the long term. Law enforcement agencies need to wake up and recognize that suppressors are not assassination tools but should be mandatory hearing protection safety equipment. 

Federal Noise Standards

Because noise-induced hearing loss (NIHL) is not immediately apparent, many law enforcement professionals leaving or retiring from their agencies are unaware of the full extent of their hearing damage. Some agencies are now just beginning to understand the link between law enforcement service and NIHL.

It may take some time and unfortunately lawsuits before law enforcement agencies and city and county governments recognize the need to suppress all weapons used on entry teams.

Enter the U.S. Department of Labor Occupational Safety and Health Administration (OSHA). These are the Federal standards and regulations for Occupational Noise Exposure:

1910.95 Protection against the effects of noise exposure shall be provided when the sound levels exceed those shown in this table when measured on the A scale of a standard sound level meter at slow response.

1910.95(b): When employees are subjected to sound exceeding those listed in the table, feasible administrative or engineering controls shall be utilized. If such controls fail to reduce sound levels within the levels detailed in the table, personal protective equipment shall be provided and used to reduce sound levels within the levels of the table.

1910.95(b)(2): If the variations in noise level involve maxima at intervals of one second or less, it is to be considered continuous.

Permissible Noise Exposures 

Duration per Day -  Sound Level (dBA)

8 hours - 90 dBA

6 hours - 92 dBA

4 hours - 95 dBA

3 hours - 97 dBA

2 hours - 100 dBA

1 1/2 hours - 102 dBA

1 hour - 105 dBA

1/2 hour - 110 dBA

1/4 hour or less - 115 dBA



Noise-induced Hearing Loss

Rock concerts, iPods, gunshots, jet engines they can all lead you down the road to a hearing aid.

Hearing loss from excessive noise—noise-induced hearing loss (NIHL)—affects about one-third of the nearly 40 million Americans who suffer from hearing loss.

NIHL is caused by exposure to either a sudden, loud noise or exposure to loud noises. A dangerous sound is anything that reaches 85 dB sound pressure level (SPL) or higher. Small arms fire ranges from 120 to 170 dB, depending on the weapon and caliber fired.

Pitch is another measurement of noise. It is the frequency of sound vibrations per second. The lower the pitch the fewer vibrations per second. Pitch is measured in hertz (Hz), which means cycles per second. When hearing loss begins, a person will, generally, first have trouble hearing high-pitched sounds.

Most people lose their hearing slowly over a 15- to 20-year period because of regular and repeated noise exposure that damages the complicated and intricate hair cells of the inner ear that interpret sound vibrations as words, music, or other sounds. Unlike the hairs on top of your head, which can be sheared off and grown back, hearing hair cells can't grow back because they are such highly developed, end stage cells.

Prolonged exposure to noise can actually change the structure of the hair cells in the inner ear, resulting in hearing loss. Tinnitus, which is the sound of ringing, roaring, buzzing, or clicking inside the head, often occurs with prolonged noise exposure damage, as well.

Hearing loss from noise can be permanent or temporary. If the hearing loss is temporary, hearing usually recovers within 16 hours of loud noise exposure.

There is a clear tendency for the ear to be more tolerant of noise at the low frequencies, as opposed to the middle and higher frequencies. The ear appears to be particularly vulnerable to frequencies in the range of 2,000 to 4,000 Hz, or even 6,000 Hz. These frequencies are likely to be generated by gunfire, explosions, and some types of aircraft noise.

Regardless of frequency, continued exposure to noise above 85 dB over time will cause hearing loss. According to the National Institute for Occupational Safety and Health (NIOSH), the maximum exposure time on a single episode at 85 dB is eight hours and at 110 dB it is 90 seconds. Noise levels above 140 dB can cause immediate irreversible hearing damage.


Lawrence Heiskell, MD, FACEP,FAAFP is an emergency physician and a 14-year reserve police officer with the Palm Springs (Calif.) Police Department and the founder and medical director of the International School of Tactical Medicine. Since the inception of the Palm Springs-based school in 1996, he has trained more than 1,500 law enforcement professionals.

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