OBJECTIVE: The aim of this study was to predetermine the discrimination standard point of distortion product otoacoustic emission(DPOAE) amplitudes, which discriminates the degree of the mild noise-induced hearing loss, and to estimate the accuracy and predictability of the discrimination standard point of DPOAE amplitudes. Therefore we were able to determine the usability of the DPOAE test in screening exam for mild noise-induced hearing loss. METHODS This study was analyzed 50 high frequency-impaired ears(from 25dB HL to 40dB HL at 4000Hz for which the response of DPOAE was not disappeared) and 81 normal ears through the correlation test between the amplitudes of DPOAE test and the threshold of the pure-tone audiometry test. RESULT The discrimination between >or=25dB and CONCLUSION DPOAE test is considered as a more efficient early prevention method against noise-induced hearing loss if this test is conducted as part of the special medical checkup of industrial workers exposed to noise.
OBJECTIVE: This study was undertaken to evaluate that noise-exposed workers have been appropriately selected for the special periodic health examination and that pure-tone audiometry has been correctly applied and the results of these have been properly analyzed. METHODS We obtained health examination data of noise-exposed workers from 48 special periodic health examination agencies. The data consisted of special periodic health examination results and audiograms that had performed examination during the latter half of 1998. We analysed the appropriateness of the subject selection for the second special periodic health examination of noise-exposed workers, the method of pure-tone audiometry, and the evaluation of audiogram. RESULTS The screening performance rate is 67.65% in the special periodic health examination of noise-exposed workers. Although 34.29 persons per agency should have had a second examination according to our criteria, only 18.44 persons were actually examined. So a third of subjects were omitted. The air and bone conduction performance rate by each frequency is 75.71 %. 24.29 % persons did not have a bone conduction and were evaluated only by air conduction. The correct use rate of symbols(right, left-unmasked AC, masked AC, unmasked BC, and masked BC) recommended by ASHA(American Speech-Language-Hearing Association) was 70.36 %. Generally air conduction threshold is equal to or higher than bone conduction threshold. In the reverse case, especially if the gap is more than 10 dB(BC-AC > 10), this is considered to be incorrect. When we applied this criteria, the result indicated that it was correct in 75.46 %. The performance rate of air masking was 15.03 %, and bone masking was 26.21 %. 7 among 48 agencies diagnosed NIHL(Noise-Induced Hearing Loss) only by air conduction, 8 performed air masking and 13 did bone masking. When compared with ISO Standard(1964) and Ministry of Labor Standard, the results of evaluation(D1, D2) on hearing loss according to hearing loss type and threshold were rather low. CONCLUSIONS Hearing Quality Assurance Program about periodic special examination agencies and examiners will continue to be needed and also the evaluation of hearing loss should be performed and controlled using accurate criteria. This will reduce the error among examiners and results in individuals by means of a standard that is capable of being accurate and reliable.
Although noise-induced hearing loss (NIHL) is the most prevalent occupational disease in Korea, only 10% of the diagnosed cases are compensated. Old (1989-94) and current diagnostic criteria, criteria for workers' compensation of NIHL in Korea, compensation formulas of American Medical Association/American association of Ophthalmology and Otolaryngology (AMA/AAOO), the Committee on Hearing, Bio-Acoustics, Biomechanics (CHABA), American Academy of Otolaryngology (AAO) recommendation were compared. Each criterion was applied on the audiomety data of 4044 workers (8023 ears), who had received the second line screening test of Special Periodic Health Examination Program for noise-exposed workers during 1991-2. First, the resulting proportions of NIHL cases by employing each criterion were compared and strength of agreement was measured using kappa value. Temporary Threshold Shift (TTS) was corrected by noise free interval, and the reduction ratio of NIHL cases was calculated. Theoretical progression model of NIHL was reconstructed from previous studies on the natural course of NIHL to evaluate the change of diagnosis result of each criterion in the model. The kappa value between old and current criteria was 0.19, 0.55 for current criteria and workers' corn. criteria, ranging from 0.08 to 0.78, highest coincidence was observed between current criteria and CHABA formula. The current criteria produce most similar results with CHABA formula. If TTS is corrected for NFI, there is about 14 % reduction of NIHL cases. The results of applying on NIHL progression model divided the formulas roughly into 3 groups, of which compensation criteria was the most, old criteria and AAO the least conservative. In conclusion. The result of 4 KHZ audiometry should be excluded in evaluation of hearing level and a new hearing conservation program should be set out. Current diagnostic criteria has an ambiguity in that managerial concept for prevention arid! purpose of compensation is mixed up. The current diagnostic criteria and compensation criteria could be incorporated'into 'a new formula which is based on the state of the art test for estimating everyday hearing disability.
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Noise-induced hearing loss in Asia Adrian Fuente, Louise Hickson International Journal of Audiology.2011; 50(sup1): S3. CrossRef
To determine the recovery time from noise-induced temporary threshold shift (TTS), a prospective field study was conducted at three worksites where workers are known to be exposed high level of noise. Subjects were selected according to answers on a questionnaire which inquired about otological history and previous noise exposure, including avocational, military and occupational exposures. After excluding employees with past otologic problems, recent exposure to high level noise, and under medications, total 92 employees participated in the study. Among 92 participants, complete consecutive audiometric examinations were carried out at 0~2 hours, 5~7 hours, 14~16 hours after worktime noise exposure on 26 participants wearing hearing protectors and 22 participants wearing no protective devices. The difference between the hearing level 0~2 hours after noise exposure and 5~7 hours is statistically significant by paired t-test(p<0.01). The median recovery times calculated from the data of 22 participants wearing no protective hearing devices are 15.6 hours at 4000 Hz, and 7.7 hours, 10.3 hours, 8.4 hours at 1000 Hz, 2000 Hz and 8000 Hz respectively. These data suggest that when measuring the pure tone audiometry for noise exposed workers, at least 16 hours noise-free interval is required.