Temporary Threshold Shift from a Toy Cap Gun

Temporary threshold shift resulting from exposure to one and five toy cap gun pistol shots was investigated using 11 normal-hearing adult subjects and one subject with a noise-induced hearing loss. The subjects fired the cap gun at arm’s length, and absolute thresholds at 4000 Hz were obtained before and after noise exposure by a fixed-frequency Bekesy technique. After exposure to one gunshot, five subjects showed a small TTS, five demonstrated no TTS, and two (including the subject with the hearing loss) exhibited negative TTS. No TTS occurred in any of the subjects after exposure to five shots. It was postulated that the small amount of TTS was due to the unexpectedly low sound pressure level produced by the cap gun and to the contraction of the middle ear muscles in some subjects prior to firing.