The impact of helmet design on sound detection and localization

Abstract

The shape and absorptiveness of a ballistic helmet changes the sound signal reaching the soldier’s ear. Although the attenuation of current helmets is minimal, soldiers have reported removing their Personnel Armor System for Ground Troops (PASGT) helmet when it was necessary to determine sound source direction. The Advanced Combat Helmet (ACH) has reduced ear coverage and absorptive internal padding that decreases localization errors. In an effort to provide more integrated headgear, the U.S. Army is testing a new, Scorpion (R4) helmet that has rings that allow the insertion of earmuffs and a modified version without the rings (R4-R). Two studies were conducted to measure the effect of these four designs on sound detection and localization. None of the helmets differed significantly in the degree of attenuation nor did attenuation correlate with localization. However, localization performance varied greatly. The current ACH and the R4-R had the least impact on localization. The older, unpadded PASGT, caused high error rates despite having the lowest attenuation. Despite being otherwise similar to the R4-R, the R4 impaired localization just as much as the PASGT and its rings increased the attenuation by more than a decibel.