Self-adjusting backup alarms in noisy workplaces

It is well known that vehicle backup alarms, used to warn and alert people located behind vehicles, can be an important source of noise pollution. In order to reduce annoyance in residents living in close proximity to industrial settings and construction sites, self-adjusting alarms are often employed. Typically, they automatically adjust above the surrounding noise in an attempt to reduce annoyance. However, there are little results in the literature demonstrating how effective such devices are in the workplace. This paper presents a study aimed at examining in details how self-adjusting alarms work and perform in typical noisy working environements. A methodology developed and tested in a laboratory allows estimating the noise emitted by the alarm alone even when installed in real noisy conditions on a vehicle using simple microphones, a recoder and a current clamp. Details of the methodology as well as results for two types of alarms (tonal and broadband) are presented and discussed.