The effect of head protectors on warning sound perception in noisy workplaces.

Abstract

The acoustic response of head protectors was assessed by means of a mecano-acoustic head simulator. The following protective devices were tested: welders’ mask, fire-fighter helmet, aluminized hood, leather hood, sand-blasting hood, dust protection hood, and emergency respirator. The tests were conducted in an hemi-anechoic chamber with a wideband noise presented at 100 dB SPL. The effect of 36 horizontal combined with 13 vertical angles of incidence was assessed. Generally speaking, head protectors are responsible for insertion gains of 5 to 10 dB in the low frequencies and for insertion losses of up to 30 dB in the high frequencies. The acoustic response of head protectors considerably varied with the angle of incidence. With the welder’s mask, when the source is coming from the rear, a systematic gain is observed at almost all frequencies; the mask acts as a low-pass filter in the frontal quadrant. These findings hold implications with respect to health and safety issues. In term of risk of hearing damage, the wearing of a head protector may significantly increase the noise exposure level of a worker. In terms of safety, such devices may interfere with signal detection in noise and sound source localization. [Work supported by IRSST.]