Abstract

The Université de Montréal's Groupe d'acoustique (GAUM) has developed the Detectsound software package to evaluate the ability of workers to detect acoustic warning signals in noisy work environments. The software takes into account the effects of long-term hearing loss and the use of hearing protection. This project therefore estimated the acoustic mitigation produced by head protection, evaluated the effect of such equipment on the ability to locate sound sources, and identified the characteristics of acoustic warning signals likely to ensure effective warning to users of head protection. The project showed that acoustic response varies considerably based on angle of incidence; when the noise comes from several directions at once, the protection reduces high frequencies and increases low and medium frequencies. Depending on the angle of incidence, the protection can screen out a noise or signal and also amplify the surrounding noise. Head protection also modifies the acoustic field around the head and greatly reduces the ability to locate sound sources, as measured among normal subjects. However, when the warning signal lasts long enough, most of the confusion in terms of safety is eliminated in situations where the subject is wearing head protection.