Oeken J, Menz D
Univ.-HNO-Klinik Leipzig.
Laryngorhinootologie. 1996 May;75(5):265-9. doi: 10.1055/s-2007-997576.
The inner ear responds to acute impact of high-intensity noise with a temporary threshold shift (TTS), which represents a reaction of the outer hair cells. That is why TTS should be detectable as changes of distortion-product otoacoustic emissions (DPOAE).
DPOAE were measured in 102 ears in 59 test subjects with normal hearing before and after definitive noise exposure (20 min of "white noise" at 90 dB HL). We also registrated the TTS (4kHz) immediately after noise and measured DP changes during a 30-min recovery period.
Typically we found a reduction of DP amplitude. It averaged between 2.0 and 2.5 dB HL in the frequency range from 2 to 5 kHz. There was no correlation between TTS and DP amplitude reduction at 4kHz. During the recovery period, individual ears showed an erratic pattern of DP amplitudes. However, a tendency toward incremental DP amplitude regeneration appeared after averaging. As many as 10% of the measured ears showed an atypical reaction with an increase of DP amplitudes. Whether the latter is due to errors in the test procedure or is evidence of a particularly stable inner ear remains to be discussed.
The results are further proof for the reaction of the outer hair cells on acute noise impact, which apparently leads to an increase of the stiffness of basilary membrane due to contraction processes. It may be possible to differentiate vulnerable inner ears from stable ones.
内耳对高强度噪声的急性冲击会产生暂时阈移（TTS），这代表了外毛细胞的一种反应。这就是为什么TTS应该可以通过畸变产物耳声发射（DPOAE）的变化检测到。
在59名听力正常的测试对象的102只耳朵中，在确定的噪声暴露（90 dB HL的“白噪声”20分钟）前后测量DPOAE。我们还在噪声暴露后立即记录TTS（4kHz），并在30分钟的恢复期内测量DPO变化。
通常我们发现DPO幅值降低。在2至5 kHz的频率范围内，平均降低2.0至2.5 dB HL。4kHz时TTS与DPO幅值降低之间没有相关性。在恢复期，各个耳朵的DPO幅值呈现不稳定的模式。然而，平均后出现DPO幅值逐渐再生的趋势。多达10%的被测耳朵表现出非典型反应，DPO幅值增加。后者是由于测试程序中的误差还是内耳特别稳定的证据，仍有待讨论。
这些结果进一步证明了外毛细胞对急性噪声冲击的反应，这显然是由于收缩过程导致基底膜刚度增加。有可能区分易损内耳和稳定内耳。
