The Measurement of the Effects of Helmet Form on Sound Source Detection and Localization Using a Portable Four-Loudspeaker Test Array

Abstract

Abstract : The objective of this research was to evaluate the effectiveness of a portable, four-loudspeaker array for assessments of helmet effects on wearer s detection and localization of sound sources. Military and civilian helmets affect the wearer s ability to detect and localize sound sources. There is industry need to evaluate auditory effects in helmet development and modification processes, but ongoing, well-controlled laboratory studies are prohibitively time-consuming and costly. A portable four-loudspeaker test array was used to compare the auditory effects of two prototype and two fielded helmets to a bare-head condition. Detection thresholds were measured for one-third-octave noise bands (125 8000 Hz). Localization performance was assessed for low-pass (500 Hz) speech sounds and high-pass (2 kHz) breaking glass sounds in the presence of two background noises. Detectability of sound sources varied both with the helmet type and the sound source type/location. Average sound attenuation across all test conditions was less than 1.5 dB for each helmet tested, but varied with frequency, reaching 7.0 dB for some helmets. Effects of helmet on sound source localization were large, significant, and varied with type of helmet.