Determination of optimal acoustic features for reverse alarms: field measurements and the design of a sound propagation model

Abstract

Reverse alarms available on the market present deficiencies with respect to their acoustic features and their placement on vehicles. It is therefore important to (1) better document sound propagation phenomena involving the backing up of heavy duty vehicles, (2) design software that can simulate the sound field generated by reverse alarms behind heavy duty vehicles, and, with this model, (3) determine the optimal acoustic and placement features. In order to meet these goals, four heavy duty vehicles (a grader, a loader, a cement mixer, and a dump truck) were each alternately equipped with five different reverse alarms. Audionumeric recordings were made on different axes behind the heavy duty vehicles. The recordings were studied with a software package allowing one to view the variation in sound pressure level as a function of the microphone placement. These field data allowed validation of a computerized model of sound propagation of reverse alarms (ALARME software), considering the phenomena of sound wave interference from the ground and sound wave deviation from the edges of the vehicles. The sound wave interference phenomena generate variations in sound pressure levels up to approximately 20 dB when one moves about 10 or more centimetres behind the vehicles. The ALARME software package can simulate these variations. The interferences are more pronounced when the alarms are positioned under the vehicles, which is often a favoured placement for truck owners.

Keywords:

• Reverse Alarms
• Safety
• Hearing
• Acoustic Propagation.