An Audiometric Approach To Noise Control

Abstract

Abstract Using pure-tone audiometry an Early Loss Index (ELI) for hearing is developed based upon quantitation of the 4000 cycle per second notch. Hypotheses based upon probability theory and age and sex specific presbycusis values are presented, diagnostic levels of hearing impairment are selected and data drawn from an industrial population of 5000 people are used to provide experimental validation of the theory. Combining the Eli with the National Research Council's Speech Average Loss (SAL) method for measuring hearing impairment in the speech important frequencies a basis is provided for prescribing occupational health measures. A simple three letter characterization of the essential audiometric findings on employees is proposed which should be quite useful in preventing the encroachment of Eli on Sal among the noise exposed.