背景：職業性噪音所引起的聽力損失大多呈現於高頻率段(4 kHz、6 kHz)，是否與高頻率噪音的暴露相關。

方法與對象：花蓮慈濟醫院職業醫學科以純音聽力檢查監測聽力損失之噪音作業工作者，以其中129例噪音四級管理個案為對象，進行與人口學與生活習慣等變項之相關分析，並從中選取人數最多之東部三產業：紙漿業、石材業及水泥業，進行職業性噪音造成之聽力損失與工作環境噪音頻譜的相關性分析。

結果：本研究顯示，所有個案最高平均聽力閾值於4 kHz、6 kHz處分別為56.8 dB、56.2dB，兩者並無顯著差異。回歸分析顯示，在4 kHz處年資、嚼檳榔習慣與聽力閾值呈顯著相關，而在6 kHz處僅抽菸習慣呈顯著相關(P < 0.05)。以產業別分組來看，紙漿業勞工聽力凹陷明顯發生於6 kHz，而石材業與水泥業勞工的聽力凹陷於4kHz、6 kHz兩處相當。水泥業勞工之聽力凹陷於4 kHz、6 kHz處，皆高於60 dB，聽力損失最為嚴重。作業環境頻譜資料顯示，紙漿業噪音音壓級從2 kHz至8 kHz逐漸升高，與另兩產業音壓級於4~8 kHz間呈現下降趨勢有所不同；因此紙漿業的高頻率噪音暴露，可能是形成聽力凹陷於6 kHz的原因之一。

結論：噪音性聽力損失與年資、嚼食檳榔和抽菸習慣相關。聽力凹陷常同時發生於4kHz、6 kHz兩處，但暴露於高頻率強噪音的工作環境，可能造成聽力凹陷向高頻率方向移動。

Background: Occupational noise-induced hearing loss (NIHL) mostly occurs at 4 kHz and 6 kHz; whether it is related to exposure to noises at specific high-frequencies is unclear.

Methods and subjects: The Department of Occupational Medicine of Hualien Tzu Chi Hospital used pure-tone audiometry to monitor the hearing loss for workers working in noisy environments. A total of 129 fourth-level management cases were used as subjects, whose demographic and audiometric data were analyzed. Subjects from pulp industry, stone industry and cement industry were selected for analysis of correlation between NIHL and noise spectra of the working environments.

Results: This study indicated that the highest average hearing thresholds of all cases were 56.8 dB and 56.2 dB at 4 kHz and 6 kHz, respectively, and there was no significant difference between both. Regression analysis showed that seniority, betel nut chewing and hearing threshold were significantly correlated with hearing thresholds at 4 kHz, while only cigarette smoking was significantly correlated at 6 kHz (P < 0.05). In terms of industry groups, NIHL of workers in the pulp industry obviously occurred at 6 kHz, while that of workers in the stone and cement industries was evenly present at 4 kHz and 6 kHz. Hearing thresholds of workers in the cement industry exceeded 60 dB at both 4 kHz and 6 kHz, which were more serious than that of workers in the other industries. Noise spectrum of the pulp industry showed a gradual increase from 2 kHz to 8 kHz, which is opposite to the downward trend between 4 and 8 kHz shown for the other two industries. Therefore, exposure to the higher frequency noises may have resulted in audiometric notch at 6 kHz for workers in the pulp industry.

Conclusion: NIHL is associated with seniority, betel nut chewing and cigarette smoking. Hearing loss often occurs at 4 kHz and 6 kHz at the same time, but exposure to high-intensity noise at higher frequencies in the working environment may lead to the shift of audiometric notch move to the higher frequencies.