Figure 2 :Firearm frequency spectra. (a) represents the one-third octave band spectra at the shooter-field microphone location for the long guns used in this study. (b) represents one-third octave band spectra at the same location for the handguns. The .30-06 rifle and 12 gauge shotgun contained energy across the broadest frequency range, and the energy from the .22 caliber rifle was restricted to frequencies above approximately 1.6 kHz. Handgun spectra were similar to each other in the high frequencies, but the nine mm auto loading handgun contained more energy in the middle frequencies while the .38 caliber revolver contained more energy in the low frequencies