Frequencies of Tinnitus and Noise of the Factory in Noise-induced Hearing Loss

BACKGROUND AND OBJECTIVES: This study was designed to evaluate relation between frequencies of noise and tinnitus in noise-induced hearing loss and to elucidate mechanism of tinnitus in noise-induced hearing loss. MATERIALS AND METHODS: Four factories were selected, of which noise frequencies were different except one factory. Preliminary screening hearing test with a pure tone audiometer on 1000 and 4000 Hz was done. And if the hearing threshold was over 40 dB, history taking, otological examination, tympanometry, pure tone audiometry on 500, 1000, 2000, 4000, 6000 Hz were done. Noise was measured in 125, 250, 500, 1000, 2000, 4000, 8000 Hz. Tinnitus was measured using 1000, 2000, 4000 Hz pure tone. RESULTS: 1) Hearing loss was most severe in the 4000, 6000 Hz range. 2) In A factory, noise was most intense on 4000 Hz, in B factory on 2000 Hz, and in C and D factory on 1000 Hz. 3) Forty-three workers (42.2%) of total 102 subjects complained tinnitus. And frequency of tinnitus was 4000 Hz in 71 ears (89.9%) among 79 ears with tinnius. CONCLUSION: Regardless of the frequency of noise, most workers complain of 4 kHz tinnitus. And it was in accord with frequency of most severe hearing loss in the noise-induced hearing loss