Effects of acoustic startle, simulated temporary threshold shift, and simulated tinnitus on sound localization and word recognition performance: A pilot study.

An unexpected loud sound can elicit an acoustic startle reflex and potentially cause a temporary threshold shift (TTS) for hearing and noise-induced tinnitus for a short period of time. This occurs, for example, with the high-amplitude noise burst that accompanies a bright light and impulsive force when police or military use a "flashbang" grenade to temporarily disable or confuse an adversary. This pilot study evaluated the effects of an unexpected loud acoustic impulse sound on human subject performance in terms of (1) word recognition in noise, and (2) sound localization, both examined in a hemi-anechoic free field with a horizontal plane 32 loudspeaker array. Eleven normal hearing, young, adult, male subjects were tested to determine whether acoustic startle, simulated TTS, simulated tinnitus, and combinations thereof, negatively impact performance. Results indicate that performance in a localization task is substantially affected by all three (and combinations) of these manipulations, whereas word in noise performance is principally degraded by TTS simulation. While these results are preliminary, due to the small sample size, the findings have potential implications for development of non-lethal flashbang grenades, i.e., without a concussive incendiary component.