Previous studies have shown the action of the acoustic reflex damps transmission of loud sound through the middle ear. These studies indicate latency of the reflex prevents it from providing protection for impulse noise because of the sharp rise time of such sounds. If the reflex could be activated prior to exposure to such sound, it should protect the ear from overload. To test this hypothesis, 24 subjects were exposed to 100 rounds of fire from .30 caliber machine gun (one round at a time) under two different experimental conditions. Time between rounds varied randomly from 2–6 sec. Under one experimental condition a 1000 cps 100 db tone was presented 200 msec before each round, ceased when the gun had fired. The other condition entailed exposure to the firing without the pre-exposure tone. The TTS's resulting from exposure under the two conditions were compared to determine the effect of the pre-exposure tone. Results show that the pre-exposure tone condition produced significantly smaller TTS, as predicted, than those obtained in the absence of the tone. These findings were related to previous literature.