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Dangerous Decibels

Noise is the enemy of communications and tactical awareness. So to improve the performance of law enforcement tactical units and protect the hearing of their highly trained operators, it's time for agencies nationwide to invest in suppressors for the weapons used by their entry teams.

Noise is an enemy of hearing, and it really does not take a lot of noise to damage your hearing. When the ears are exposed to extremely loud noise, inner ear structures can be damaged, sometimes permanently. This medical condition is called Noise Induced Hearing Loss (NIHL).

Noise is also the enemy of communications and tactical awareness. So to improve the performance of law enforcement tactical units and protect the hearing of their highly trained operators, it's time for agencies nationwide to invest in suppressors for the weapons used by their entry teams.

Current law enforcement tactics require that tactical team members be in very close proximity to one another as they search a structure for suspects. That means that weapons are typically held a few inches away from the ears of team members as each threat area is searched and cleared.

During such an operation, the immediate threat area is often flooded with multiple team members, carrying pistols, submachine guns, and assault weapons. A discharge of any of these firearms to engage or neutralize a threat is more than sufficient to produce a devastating irreversible noise injury to the hearing of the officers involved, especially those officers whose ears are inches away from the weapon. Repeated shots fired will inflict further damage on officers' hearing.

This devastatingly painful sound also has tactical implications. It disorients, distracts, and impairs the ability of the tactical operator to make split-second decisions. What that means is that when shots are fired, the team has been essentially "flash-banged," giving its opponent a tactical advantage. Think about the implications of what the team is facing if a motivated shooter (or shooters) understands and uses the effects of noise on their opponents.

While the tactical officer is focused on recovering from the noise injury, he is at a disadvantage and has lost his ability to focus on the threat. In addition, when multiple shots are fired in a close environment, there is always the risk of contagious fire and the sympathetic response from other startled officers to pull the trigger and inadvertently discharge their weapons.

Today, most entry teams do very little to protect their hearing should shots be fired. Some operators wear radio ear pieces on one of their ears, but this offers little protection against the report of any weapon at close range. Typically, the operators leave their non-radio ears unprotected to enhance their tactical awareness.

Some agencies require that tactical officers wear some form of hearing protection in the ear opposite the radio earbud. That may preserve an officer's hearing, but it diminishes tactical awareness, and the quality of protection that it offers can vary widely.

I believe that a better solution to this problem is to fit the primary weapons used by entry team members with suppressors.

The best suppressors can reduce the report of a weapon by more than 30 decibels (dB). That may not seem to be a significant difference. However, the decibel measurement of sound is logarithmic, which means that a 30 dB drop is actually a 1,000-percent reduction in sound.

When mounted on pistols and submachine guns using subsonic (slower than the speed of sound) ammunition, a good suppressor can reduce the sound to roughly comparable to a staple gun. Often the sound of the gun's bolt cycling is louder than the actual report.

A good example is the Heckler & Koch MP5SD. This integrally suppressed submachine gun used by many law enforcement agencies drops the bullet's speed to approximately 850 feet per second and eliminates the supersonic crack, as the bullet does not exceed the speed of sound at approximately 1,150 feet per second.

Suppressors are particularly useful in enclosed spaces where the sound, flash, and pressure effects of a weapon being fired are amplified, such as in a close quarter battle (CQB) in a mobile home or in tubular assaults (buses, trains, and planes). Such effects will disorient the shooter, affecting concentration and accuracy, and can permanently damage hearing very quickly.

Some of the newer suppressors on the market can even improve minute-of-angle accuracy and may increase bullet velocity by as much as 30 to 50 feet per second.

There is also a further tactical benefit. A suppressor eliminates the muzzle flash, depending on the specific ammunition fired. This could be a very important advantage during tactical operations under low-light conditions, since some well-trained criminals know to identify and shoot at muzzle flashes. Another reason to reduce muzzle flash is to minimize explosion danger during warrant service in a location that is suspected of being a clandestine drug lab. A muzzle flash in this environment can be catastrophic for everyone in the room or even the building.


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.