Toward a measure of auditory handicap in the Army

The effect of a soldier's ability to hear on the capacity to perform a mission was calculated for a variety of militarily relevant tasks through the use of mathematical models. Changes in hearing can result from organic loss, hearing protectors, the masking effect of noises, etc. The effects were calculated for the detection of sounds of enemy personnel (speech, movement noises) or their equipment (rifle bolt, tank, generator). We also calculated the effects on the ability to control/communicate with troops verbally. The normal ear is highly effective in detecting noises of personnel or their equipment or in understanding speech, even in noise. By contrast, even modest hearing losses and/or the wearing of hearing protectors can have profound effects on military performance, for example, reducing the area that can be monitored acoustically by more than 30-fold or cutting warning times for other sounds by a factor of more than 100. Hearing protectors may have the conflicting effects of protecting hearing while producing unacceptable performance because of their attenuation.