Classification of the level and the type of hearing loss based on the analysis of audiograms of workers exposed to high level of occupational noise

S.M.N. Sethunga, J.A.P. Bodhika, U.I.P. Abeysuriya, W.G.D. Dharmaratna, S.A. Wickramasingha


This paper presents some health effects of workers exposed to high occupational noise for a long period. The main objective of this study was to classify the level and the type of hearing loss of such workers plus to study the effects on their health. Out of a sample of 99 workers exposed to 85 dB(A) or more occupational noise, 73 (74%) workers who were exposed over 40 hours per week for five years or more were selected for this study. Their hearing levels were tested audio-metrically and audiograms of Air Conduction (AC) and Bone Conduction (BC) measurements were taken. Depending on the degree of Hearing Loss (HL) of audiograms, the sample was classified into Normal hearing (0-25 dB(A)) : 10.5%, Mild HL (26-40 dB(A)) : 67.0%, Moderate HL (41-55 dB(A)) : 21.75%, Moderate-to-severe HL (56-70 dB(A)) : 0.75%. None of these fall in to Severe HL or Profound HL categories. Based on the HL and the configuration of audiograms of AC and BC measurements, 89.5% of the sample was classified as Conductive Hearing Loss (CHL 2.25%), Sensorineural Hearing Loss (SNHL 85.75%), and Mixed Hearing Loss (MHL 1.5%). Some SNHL samples were identified as Meniere’s disease 19%, Acoustic Trauma 12%, and Noise-Induced Hearing Loss (NIHL) 6%. NIHL were recorded among highly exposed workers to noise in the frequency range 3000-6000 Hz. Percentage statistics of various levels of hearing levels along–with associated symptoms based on the response to the questionnaire are also presented.
Keywords: Noise exposure, Health impacts, Audiometric hearing test, Hearing threshold shift

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