摘要
众所周知，过多过强的噪声暴露常引起噪声性听力损失，继而导致噪声性聋(Noise-induced hearing loss，NIHL)。随着现代工业社会的发展，噪声性聋已成为目前临床上极为常见的一种疾患。引起噪声性聋的原因很多，主要分为职业性和非职业性噪声暴露。近年来人们在重视职业性噪声防治的同时，非职业性噪声暴露引起噪声性听力损失的危害也逐渐引起了学者们的广泛关注。这些非职业性噪声主要包括随身听装置的使用、迪厅或卡拉OK厅娱乐、射击和摩托车等。其中在日常生活中青少年普遍使用随身听来欣赏音乐和学习外语。噪声性听力损失分为暂时性阈移(Temporary threshold shift，TTS)和永久性阈移(Permanent threshold shift，PTS)。暂时性阈移(TTS)在脱离噪声环境后是可以恢复的，而永久性阈移(PTS)即使脱离噪声环境也不会恢复，最终演变成噪声性聋。随身听装置极可能导致永久性阈移(PTS)，同时可伴有耳鸣的存在。因此探寻早期监测噪声性听力损失的方法在预防方面便显得尤为重要。
传出神经系统功能的研究表明它对耳蜗的精细调节起着重要的作用，尤其是噪声状态下耳蜗功能的调节。为此一个问题摆在我们的面前：早期噪声性听力损失者其传出神经系统功能是否会受到影响，能否作为噪声性听力损失监测的一种敏感指标?
因此本课题采用常频纯音听阈测试和扩展高频纯音听阈测试对一群青年随身听使用者的听力进行检测，以了解使用随身听对正常青年人听力的影响，筛选出听力受损人群，分析其使用时间与使用强度与其听力损失之间的关系。以耳声发射及蹬骨肌反射为电生理指标，结合对侧声刺激的方法对其听觉传出神经系统功能进行评价，全文由两部分组成。
第一部分 采用常频纯音听阈测试(0.5-8kHz)和扩展高频纯音听阈(8-20kHz)测试方法对一群正常青年人的听力进行测试，观察随身听的使用对正常青年人听力的影响。本研究结果显示有14.1％(34／240耳)的受试者出现了不同程度的听力损失，且观察组(随身听的使用时间＞7小时／周)与对照组(随身听的使用时间＜7小时／周)相比，其各频率的听阈均高于对照组(P＜0.05)。观察组中常频听阈异常者(0.5k-8k有一个或数个频率纯音听阈＞25dBHL)的扩展高频听阈高于常频听阈正常者。通过真耳分析仪对使用者的使用声强和随身听装置的最大输出声强进行
测试，结果表明，各种随身听的最大输出声强范围为91.4一106.1dB(A)之间。听闽
正常者的随身听习惯使用强度要高于听闽正常者。本研究的结果提示，随身听的
使用很可能对青年人的听力造成损害，且这种损害是与时间及使用强度相关的:
扩展高频纯音听阐测试可以作为对噪声暴露后早期听力损害的一种监测方法。
第二部分采用Celesta一503型耳声发射仪以及GSI~33型中耳功能分析仪对
第一部分中筛选出来的对照组受试者、常频听闽正常者和常频听闻异常者进行测
试。测试项目包括在有及无对侧宽带噪声(70dBSPL)的情况下测试受试者的畸变
产物耳声发射(Distortion produet otoacoustie emission，oPoAE)和瞬态诱发耳声
发射(肠ansient evoked otoacousti。emission，TEoAE)的幅值以及蹬骨肌声反射
(Acoustic stapedius reflex)的幅值的改变对传出神经系统的功能进行评估。结果
表明，听闽异常组受试者的DP·gram和1/0曲线的高强度部分以及TEoAE的总幅
值均低于对照组受试者(P<0.05)，听闽异常组蹬骨肌声反射的闲值高于对照组
(P<0 .05);加对侧噪声后听闭异常组耳声发射和蹬骨肌声反射的幅值抑制幅度均
低于对照组(P<0.05)。本研究结果表明噪声暴露后引起的早期听力损害后其听觉
传出神经系统功能明显降低。对听觉传出神经系统功能的评价可以用于监测噪声
暴露后的早期听力损害。
本课题研究的结果表明，随身听的使用会对听力造成损害，扩展高频纯音听
阂测试可以作为对噪声暴露后早期听力损失进行监测的方法。噪声暴露后引起的
早期听力损失伴有听觉传出神经系统功能明显降低，因此我们认为对听觉传出神
经系统功能的监测极可能用于噪声暴露后听觉功能损害的评价。
Long term exposure to excessive noise will cause noise-induced hearing loss (NIHL). NIHL has become a most common disease as the developing of the modern society. There are many causes of NIHL. The most popular factor is occupational noise exposure. In the past twenty years, the potential hearing damage hazard from exposure to non-occupational noise (leisure noise) raised intensive attentions. Non-occupational noises include listening to portable cassette player, CD player, and MP3 player and so on. NIHL can be divided into temporary threshold shift (TTS) and permanent threshold shift (PTS). The TTS can soon recover if we break away from noise exposure. The PTS cannot recover although we break away from noise exposure. The NIHL sometimes accompany tinnitus. So it is important to seek a method to detect the early noise-induced hearing loss.
The investigation of the efferent system reveals that it serves an important role in accurate modulating of the cochlear functions, especially in noise environment. We should solve two problems. One is whether exposure to noise can change the functions of the efferent system, and another is whether the efferent system function test can be used as a method to detect the early NIHL.
The hearing thresholds of personal listening devices users are obtained by using conventional pure-tone audiometry and extended high frequency pure-tone audiometry in present study. The NIHL patients are picked up from the subjects. The relation between the intensity of the personal listening devices and the hearing loss are investigated . The efferent system functions are tested by contralateral acoustic stimulation. The present study is composed of two parts.
Part one Personal listening devices and hearing loss
The hearing thresholds of the subjects are obtained by using conventional audiometry and extended high frequency pure-tone audiometry. The results reveal that the hearing thresholds of 14.1%(34/240 ears) of the subjects have risen in some extent. The hearing thresholds of the observation group subjects are higher that of the control group subjects. The maximal available sound levels from the personal listening devices are tested by Auricle real ear test equipment. The results indicate that long-term use of the personal listening devices can cause the hearing loss. Extended high frequency audiometry can be used as a method to detect the early NIHL.
Part two Efferent system and NIHL
Distortion product otoacoustic emission (DPOAE) and transient evoked otoacoustic emission (TEOAE) are tested with Celesta-503 otoacoustic analyzer. The stapedius acoustic reflex is tested with GSI-33 audiometer. The amplitudes of the DPOAE and TEOAE of the observation group are lower than that of the control group. The amplitude decreases of the DPOAE and TEOAE of the observation group are lower than that of the control group. The test of efferent system functions can be used as a sensitive method to detect the early NIHL.
In conclusion, this study indicates that long-term use of personal listening devices can cause NIHL. The extended high frequency audiometry and efferent system function test can be used as sensitive method to detect the early NIHL.
引文
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