Comparison of different vehicle backup-alarm types with regards to worker safety

摘要

Audible backup alarms installed on mobile equipment are used to warn or alert nearby workers. Still, accidents and fatalities involving vehicles in reverse are reported every year (Murray et al. 2007; NIOSH 2004; Blouin 2005). Two important factors may affect the effectiveness of backup alarms on workers safety (Laroche 1995). Firstly, the uniformity of the sound field behind the vehicle is not guaranteed, in particular for tonal alarms. Secondly, spatial localization of the alarm can be a problem, particularly for workers wearing hearing protectors. Additionally, the noise generated by such devices will propagate and, quite often, be a source of nuisance for residents living in close proximity. In recent years, a new type of vehicle backup-alarm has been drawing increasingly more interest from many industrial sectors. The new alarm, based on the use of broadband noise instead of the typical tonal ("beep") signal, is deemed to reduce environmental noise annoyance close to industrial settings and construction sites and to be more efficient for spatial localization and uniform noise propagation behind vehicles. While conceptually appealing, few published and peer-reviewed scientific studies have demonstrated the advantages and disadvantages of such an alarm to ensure worker safety, particularly in comparison to existing technologies (Burgess & McCarty 2009; Homer 2008; Withington 2004). This two-part study was intended to compare three types of backup alarms: the standard tonal signal, a multi-tone signal and the broadband noise technology. The first part, performed in the field, focused on objective measurements of the sound propagation behind vehicles for various vehicles and terrain configurations. The second part, performed in a laboratory environment, was centered on the measurement of various psychoacoustic metrics (hearing threshold, loudness, and perceived urgency), as well as the study of spatial localization tasks. The paper presents the methods used for the "field" and "laboratory" parts. Results illustrating some of the findings, both from the field and from the psychoacoustic standpoint, are finally presented.