| Summary: | 碩士 === 國立臺北護理健康大學 === 語言治療與聽力研究所 === 105 === This study aimed at investigating changes in hearing acuity incurred by soldiers due to high-intensity impulse noise exposure during artillery exercises. The relationships between hearing acuity and high-intensity impulse noise exposure experiences, exposure noise level, and wearing hearing protection devices were discussed. The case-control study was conducted on 169 soldiers who were randomly selected from an annual artillery exercise and agreed to participate in the study. Ninety-eight individuals were new hands (without previous exposure history), whereas the other 71 soldiers were skilled old hands (with previous artillery exposure histories) in artillery exercises. Hearing measurements, including the conventional pure-tone thresholds at frequencies from 0.25 to 8.0 kHz at intervals of one octave (including 3.0 kHz and 6.0 kHz), extended high-frequency audiometry from 9.0 to 18 kHz, and distortion-product otoacoustic emissions (DPOAEs), were performed prior and immediately after noise exposure and a week later. Data were analyzed using descriptive statistical methods, paired t-test, and Pearson product-moment coefficient.
The results showed a negative correlation between the pure-tone threshold average and level of DPOAEs. Elevated pure-tone thresholds and decreased DPOAE levels were noted in soldiers after heavy artillery noise exposures within 24 h and a week later. Significant elevation of audiometric thresholds and decreased DPOAE levels in the skilled group were observed as compared to that in the new hand group, suggesting that low-frequency artillery noise exposure did play a role in damaging hearing acuity. In addition, subjects with earplugs fitted showed benefits in hearing protection only in the left ear compared with those who did not use earplugs during the exercise, implying that whether earplugs are adequately fitted would be a major issue in interpreting the current data. When soldiers were divided into an extremely high noise group (noise level range of 165.6–204.7 dB SPL) and a high noise group (164.7–172.3 dB SPL), no significant difference in threshold shifts between these two groups was observed as compared with after noise exposures.
Given that impulse noise exposure in early adulthood does deteriorate the hearing thresholds and may accelerate age-related hearing loss, prevention of noise and noise-induced hearing loss in the military is imperative. The purpose of this work was to provide information on the artillery exercises’ effects on heading, which also highlights the necessity and urgency of implementing military hearing conservation programs in our country.
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