Effect of Electronic ANR and Conventional Hearing Protectors on Vehicle Backup Alarm Detection in Noise

Abstract

An experiment was conducted wherein masked thresholds (using ascending method of limits) for a backup alarm were obtained in pink and red noise at 85 and 100 dBA for 12 participants immersed in a probability monitoring task and wearing a conventional passive hearing protection device (HPD, an earmuff or a foam earplug), an active noise reduction (ANR) headset, or no HPD at all (only in 85 dBA noise). Results revealed statistically significant between-HPD differences in red noise (from 2.3 to 3.1 dB) and in the 100-dBA noise level (from 2.6 to 4.3 dB). An additional finding, which corroborates other studies using different protocols, was that masked thresholds in 85-dBA noise were significantly lower (from 3.2 to 4.4 dB) for the occluded conditions (wearing an HPD) than for the open-ear (unoccluded) condition. This result refutes the belief among many normal-hearing workers that the use of HPDs in relatively low levels of noise compromises their ability to hear necessary workplace sounds. Actual or potential applications of this research include (a) the selection of appropriate HPDs for low-frequency-biased noise exposures wherein signal detection is important and (b) gaining insight into the appropriateness of ANR-based HPDs for certain industrial noise environments.

The challenge of localizing vehicle backup alarms: Effects of passive and electronic hearing protectors, ambient noise level, and backup alarm spectral content

“…[6,9] A single prior study actually examined, on a subjective basis, the effect of the backup alarm's acoustic features on how workers perform in localizing the source of the signal. In this study, Withington [8] used self-report measures to assess workers' performance in localizing conventional backup alarms as well as broadband ones.…”

Comparison of sound propagation and perception of three types of backup alarms with regards to worker safety

“…[34][35][36][37] They can however reduce speech discrimination in background noise levels lower than 80 dBA, even in normal hearing listeners, [36][37][38][39] and particularly hinder sound detection [40] and speech perception [41] in individuals with hearing loss. For example, Robinson and Casali [40] showed that a tonal alarm could remain audible at fairly low SNRs (0 dB) in noise levels greater than 85 dBA when passive earmuffs are used, even in the presence of significant hearing loss (45-50 dB HL), indicating that workers with such hearing loss should hear the alarm if ISO 7731 [33] is met (alarm level exceeding that of the background noise by at least 15 dB).…”

Speech recognition in noise with active and passive hearing protectors: A comparative study

“…However, studies designed to simulate onthe-job listening conditions have reported poorer audibility with standard earplugs (Casali et al, 2004). As regards hearing impaired subjects, Abel et al (1982Abel et al ( , 1993 demonstrate that wearing earmuffs or earplugs deteriorates word recognition in noise when a high-frequency or flat sensorineural hearing loss is present.…”

“…To the authors' knowledge, only limited research has been published concerning communication with these protectors and the studies usually fail to establish univocally their benefits on signal perception in noise over standard passive protectors (Abel et al, 1993;Abel and Spencer, 1997;Casali et al, 2004;Dancer et al, 1999;Dolan and O'Loughlin, 2005).…”