Effect of hearing protection and hearing loss on warning sound design

Warning sound devices are commonly used in noisy workplaces to warn workers of potentially dangerous situations. Warning sound perception depends on many factors, including warning sound levels relative to the background noise, hearing protection and hearing status. Although national and international standards (i.e. ISO 7731) are available to guide the choice of warning sound devices, none appears to take into account all these factors within a comprehensive model. A software tool, Detectsound, was used to demonstrate the extent to which hearing protection can compromise the perception of warning sounds by workers with hearing loss. Detectsound yields desired target sound levels at different workstations for different workers using and for various conditions of hearing protection. Scenarios were constructed using a low-frequency noise spectrum from NIOSH database, different degrees of sensorineural hearing losses, and personal hearing protector attenuation measurements or estimates according to the manufacturer’s data. Detailed analysis of realistic scenarios with Detectsound revealed that a flat and high frequency sensorineural hearing loss combined with hearing protection can compromise high frequency perception and lead to overprotection. Such realistic scenarios make it explicit that the configuration of warning devices can vary significantly depending on the hearing status of workers at a given workstation and the variability in attenuation provided by hearing protectors.