Vehicle Backup Alarm Localization (or Not): Effects of Passive and Electronic Hearing Protectors, Ambient Noise Level, and Backup Alarm Spectral Content

Abstract

A parametric human factors experiment employed a hemi-anechoic sound field in which listeners were required to localize a vehicular backup alarm warning signal in 360-degrees azimuth. Measures of localization performance included: 1) percentage correct localization, 2) percentage left/right localization errors, 3) percentage front/rear localization errors, and 4) the absolute deviation in degrees from the alarm's location. In summary, the data demonstrated that normal hearing listeners did not improve in their ability to localize the backup alarm warning signal in 360-degrees azimuth when wearing augmented hearing protectors (including dichotic sound transmission earmuffs, flat attenuation earplugs, and level-dependent earplugs), as compared to when wearing conventional passive earmuffs or earplugs of the foam or flanged types. Furthermore, a diotic sound transmission earmuff resulted in the poorest localization. Localization was also degraded in 90 dBA pink noise, as compared to the relatively quiet condition of 60 dBA pink noise. An augmented backup alarm which incorporated 400 Hz and 4000 Hz components to exploit the benefits of interaural phase and intensity cues slightly improved localization compared to the standard, more narrow-bandwidth backup alarm, and these results have implications for the updating of backup alarm standards.