Hearing Loss

It is generally accepted that a continuous noise level of 85 db (decibels) is the maximum safe level for long-term exposure to steady noise level within the frequency range of about 600-1,200 Hz. The very brief gunfire noises are another matter.

Leading hearing specialists stipulate that about 150 db is the maximum peak limit for gunfire noises without impairment of speech perception and 140 db maximum without impairment of good hearing of music and the like.

It should be noted that decibels are a logarithmic scale and that the sound energy doubles with each 3 db increase.

Below are listed data describing peak sound pressure levels produced by firearms of various calibres. With the introduction of muzzle breaks and porting, the risks of hearing loss dramatically increase (Tables 8.A.2-10.4).

Dr. Krammer1 states that the damage caused by one shot from a 0.357 Magnum pistol, which can expose a shooter to 165 dB for 2 ms, is equivalent to over 40 h in a noisy workplace.

1 Dr Krammer, Ball State University, Muncie, Indiana, USA.

Table 8.A.3 Shotgun noise data.

d B

0.410-Bore 28" barrel

150

26" Barrel

150

18" Barrel

156

20-Gauge 28" barrel

152

22" Barrel

154

12-Gauge 28" barrel

151

26" Barrel

156

18" Barrel

161

12" Barrel

168

8" Barrel

172

Table 8.A.4 Centre fire rifle data.

0.223, 18" Barrel 155

0.243 in 22" barrel 155

0.30-30 in 20" barrel 156

7 mm Magnum in 20" barrel 157

0.308 in 24" barrel 156

0.30-06 in 24" barrel 158

0.30-06 in 18" barrel 163

0.375 18" Barrel 162

0.375 18" Barrel with muzzle brake 170

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