Overview of the acoustics and psychoacoustics of reverse alarms installed on moving vehicles

Abstract

Audible alarms are often used on mobile equipment to alert nearby workers of safety risks, in particular with reversing vehicles. A prompt reaction to the alert is required but depends on many technical factors (e.g., mounting location on vehicle), acoustic factors (e.g., alarm emission level, sound propagation pattern behind the vehicle) and psychoacoustic factors (e.g., perceived urgency, ability to localize alarm, effect of hearing loss and hearing protection). These factors are not fully addressed in applicable regulations or standards. This paper presents an overview of the main results of a series of research studies carried out as a collaborative effort by the "Institut de recherche Robert-Sauvé en santé et sécurité du travail" in Montreal and the University of Ottawa in the past twelve years. A main objective was to compare the relative benefits of two types of alarm signals, the widely-used conventional tonal signal and the relatively recent, but emerging, broadband signal. Overall, results indicate that the broadband alarm presents some benefits such as more uniform acoustic propagation patterns, lower alarm reaction thresholds and better sound localization compared to the tonal alarm. The latter two advantages are emphasized when hearing protectors are worn.