Noise‐Induced Hearing Loss in Working Environment and its Background

Abstract

Noise‐Induced Hearing Loss in Working Environment and its Background: Ikuharu Morioka, et at. Department of Hygiene, School of Medicine, Wakayama Medical University—The excessive exposure to noise results in temporary and/or permanent changes in hearing ability in both human and animal subjects. The noise‐induced hearing loss in workers was previously known as industrial deafness and it is still an important problem in occupational health. The purpose of this review is to describe the major findings obtained in epidemiological and experimental studies on the effects of noise in the working environment on man. The discussion begins with a classification of noise‐induced hearing loss and the background of hearing impairment in workers. The degree of noise‐induced hearing loss depends on both the characteristics of noise and the individual sensitivity to noise. Factors related to noise‐induced hearing loss are reviewed. When the hearing ability is evaluated among aged workers, presbycusis cannot be ignored. Important new evidence is reviewed on hearing impairment caused by both aging and noise‐induced hearing loss. Exposure to intensive noise changes the structure and function of the basilar membrane, sensory hair cells, the tectorial membrane and tip links, and the cochlear blood flow. The pathology and pathophysiology of noise‐induced hearing loss are also explored. Relation between exposure to noise and hearing impairment is discussed to predict the effects of longterm exposure. Finally, the diagnosis and prevention of noise‐induced hearing loss are reviewed.