NOISE-INDUCED HEARING-LOSS IN AN AUTOMOBILE SHEET-METAL PRESSING PLANT - A RETROSPECTIVE INVESTIGATION COVERING 25 YEARS

Hearing damage suffered by male workers in an automobile sheet-metal p ressing plant has been studied on five occasions during the period 196 4-89. The hearing threshold data have been analysed in order tb determ ine hearing loss due to noise in various age groups. The hearing thres holds were better on later occasions. In the youngest group of workers only 45% exhibited normal hearing in 1964, while in 1989 the correspo nding figure was 88%. The same tendency towards improved hearing could also be seen in the age groups 30-39 and 40-49 years. In the oldest a ge group, 50-59 years, hearing handicap decreased from 58% in 1964 to 11% in 1989. With the aid of the average hearing: loss, it has also be en possible to estimate the equivalent noise level to which present-da y workers have been exposed, as well as the reduction in level of expo sure during the past 25 years. The effects of a long-term technical an d medical occupational health care programme including noise-reduction measures and improved use of hearing protectors are discussed.