In this study, researchers analyzed the acoustical characteristics of several common firearms in a quasi-anechoic environment at a high sampling rate.
In this study of acoustical characteristics of common firearms, the authors developed a quasi-anechoic procedure to capture gunshot signals at a very high sampling rate (500 kHz samples per second) using 12 microphones covering 180° in azimuth. Based on analysis of the recorded data, the authors found that acoustic gunshot signals vary from one firearm to another in terms of peak sound pressure and Muzzle blast duration. For a given firearm, the researchers observed significant differences in sound level and also Muzzle blast duration as a function of azimuth and find that there is measurable variation in signal details among successive shots from the same firearm. The recordings were made in an open-air environment with a raised shooting platform and microphone position, resulting in sufficient delay between the arrival of the direct sound at the microphones and the arrival of the first reflection (from the ground). The firearms used in this experiment included a Remington 870 shotgun, 308 Winchester rifle, AR15 rifle, and a 22LR rifle. Handguns tested include a Colt 1911A1, Glock 19 with 9mm ammunition, Glock 23, Sig 239, and a Ruger SP101 with both 357 Magnum and 38 Special ammunition. A number of successive shots were record for each of the firearm type. A typical gunshot signal includes two high amplitude and short duration impulsive signature sounds, the muzzle blast, observed in all the gunshot waveforms, and the bullet s shock wave, which can only be detected if the bullet travels at supersonic speed. Audio recordings from a shooting incident may provide crucial information for a criminal investigation.