Anaoysis of latency and frequency component of evoked otoacoustic emission

为了详细研究耳声发射（eoae）的特性，我们介绍了一种新的频率分析方法（100 Hz harlow -band eoae分析）：使用双通道可变滤波器，在1.0至2.0 kHz的频率区域内，通过100 Hz通频带宽度步进滤波，对点击刺激的一系列十个回声响应进行滤波。在本研究中，我们研究了正常耳、突发性耳聋和梅尼埃耳的耳廓声源的特性。结果表明：1)正常耳声发射由两个主回波序列和若干次回波序列组成。主要回波列分为潜伏期小于10 msec的快速分量和潜伏期大于10 msec的慢速分量。在高于1.5 kHz的频率范围内检测到快速成分，在低于1.4 kHz的频率范围内检测到慢速成分。虽然快速分量和慢速分量都表现出非线性特性，但慢速分量的检测阈值相对较低，通常在0 dB nHL以下，在20 - 30 dB nHL左右饱和。2)在突发性耳聋或梅尼埃氏病的早期，在听力损失大于50db HL的严重耳部，通常可以检测到100hz窄带eoae。但有这些病变的耳部eoae的慢速分量通常振幅较小或不存在，因为慢速分量比快速分量更容易受到伤害。3)在梅尼埃病或突发性耳聋早期，慢速成分的持续存在预示着听力损失预后良好。4)在正常耳中存在的非线性特征在病变耳中消失。因此，使用非线性咔嗒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.