Occupational Noise Induced Hearing Loss and Hearing Threshold Profile at High Frequencies

Abstract

Background: The textile workers exposed to industrial noise are prone to develop hearing loss concentrated mainly at high audible frequencies. It is affected by duration of exposure and type of noise. Aims: Present study was conducted to (a) investigate hearing thresholds of textile workers by pure tone audiometry, (b) correlate thresholds at 4 kHz, 6 kHz and 8 kHz between noise exposed and unexposed group and (c) study effect of duration of exposure on hearing profile. Materials and Methods: A cross-sectional study was carried out on 50 weavers of plastic industries exposed to high levels of constant noise. Objectively, hearing defects were inquired by self-administered questionnaires. Subjectively, pure tone audiometry was carried out to measure hearing thresholds at various frequencies. It was simultaneously compared with the similar data of matched control group. Results: Prevalence of hearing loss symptom and hearing thresholds were more in exposed group than in control group. There was significant hearing loss at high frequency as compared to lower ones. Audiometry revealed notch at 4 kHz with less effect at 6 or 8 kHz, cumulative effect of duration of exposure. Conclusion: Textile weavers are more at risk to develop Occupational Noise Induced Hearing Loss (ONIHL) mainly affecting higher frequencies concentrated at 4 kHz. Despite least effects on hearing, this disease silently progresses and there is a definite scope of prevention by appropriate protective measures.