Effect of wearing hearing protectors on the audibility of railway warning signals - an experimental study.

The effect of wearing hearing protectors on the audibility of warning signals has been evaluated for three specific railway-related jobs: track workers, train drivers and platform agents. Masked thresholds were measured in the laboratory, on railway agents with normal hearing, using warning signals and background noises typical of each job. Out of the 36 situations tested in total, statistical analyses showed that wearing earplugs improves the perception in 11 situations, deteriorates the perception in 10 situations and has no significant effect in 15 situations (as compared to no hearing protector). The deteriorations essentially concern signals which have no (or not enough) energy in the low-frequency range (f< 1500 Hz) when they have to be heard in background noises which dominate in the low-frequency range. To prevent the deteriorations, these signals could be modified by adding some energy in the low-frequency range (f< 1500 Hz).