Anaoysis of latency and frequency component of evoked otoacoustic emission

为了详细研究耳声发射（EOAE）的特性，本文介绍了一种新的EOAE频率分析方法（100 Hz耙带EOAE分析）：在1.0 ~ 2.0kHz的频率范围内，用双通道可变滤波器对10个声刺激回波信号进行100 Hz阶跃滤波。在本研究中，我们调查EOAE的属性从正常耳和突发性耳聋和梅尼埃病的耳朵。结果表明：（1）正常耳EOAEs由两个主回波串和多个次回波组成。主要的回波序列被分为快速成分与短的潜伏期低于10毫秒和慢成分与长的潜伏期超过10毫秒。在高于1.5 kHz的频率范围内可清楚地检测到快分量，在低于1.4 kHz的频率范围内可清楚地检测到慢分量。虽然快、慢成分均表现出非线性特征，但慢成分的检测阈值相对较低，通常低于0 dB nHL，在20 ~ 30 dB nHL左右达到饱和。2）在突发性耳聋或梅尼埃病的早期，100 Hz窄频带EOAE常可从听力损失大于50 dB HL的耳中检测到。3）在梅尼埃病或突发性聋早期，慢成分持续存在提示听力损失预后良好; 4）正常耳EOAES的非线性特征明显，而病变耳EOAES的非线性特征消失。因此，使用非线性咔哒声序列无法从病理耳中检测到EOAE。

In order to investigate the properties of otoacoustic emissions(EOAEs)in detail, we introduced a new method for frequency analysis of EOAEs, (100 Hz harrow-band EOAEs analysis) : a series of ten echo responses to click stimuli, filtered by a 100 Hz step of pass-band width in the frequencyregions from 1.0 to 2.0 kHz with the use of a dual channel variable filter. In the present study, we investigate the properties of EOAEs from normal ears and from ears with sudden deafness and Meniere's disease. The results were as follows :1)EOAEs from normal ears were composed of two main echo trains and several subechoes. The main echo trains were divided into fast components with short latency below 10 msec and slow components with long latency over 10 msec. The fast component was detected clearly in the higher frequency ranges than 1.5 kHz, the slow component in the lower frequency ranges than 1.4 kHz. Although both fast and slow components showed nonlinear properties, the slow component had a relatively low detection threshold, usually below O dB nHL and saturated around 20 - 30 dB nHL.2)In an early stage of sudden deafness or Meniere's disease, 100 Hz narrow-band EOAEs could often be detected from ears with a severe hearing loss greater than 5O dB HL. But slow component of EOAEs from ears with these lesions was usually small in amplitude or absent, because slow component was more vulnerable than fast component.3)In Meniere's disease or early of sudden deafness, the persistence of slow component indicated a good prognosis of hearing loss.4)Nonlinear property of EOAES, marked in normal ears, was lost in lesioned ears. Therefore, EOAEs could not be detected from a pathologic ears with use of nonlinear click sequence.