Abstract
For several years a Hearing Conservation Program at The Dow Chemical Company has used a noise exposure profile system to characterize four categories of severity of on-the-job exposure to noise. Audiometric data have been gathered over a 12-year period for employees working on jobs that are classified according to the established profile system. Hearing loss trend curves developed by longitudinal analysis within the available range of audiiometric findings and age distribution of the study population show that: (1) The most sensitive frequency to noise for all levels of exposure is 6000 Hz. (2) The progression of hearing loss from intermittent exposure to noise is gradual, occurring over a period of several years. (3) Men with similar first measured hearing losses, regardless of initial age, lose hearing at approximately the same rate. (4) There is a distinct difference in the expected hearing loss among different levels of intermittent noise exposure as classified by the noise exposure profiles.