Anaoysis of latency and frequency component of evoked otoacoustic emission

为了详细研究耳声发射的特性，我们介绍了一种新的耳声发射频谱分析方法--100 HzHarrow频段EOAEs分析：对短声刺激的一系列10个回声响应，用一个双通道可变滤波器在1.0-2.0 kHz的频率范围内以100 Hz的通带宽度阶跃进行滤波。在本研究中，我们研究了来自正常耳和突聋和梅尼埃病耳的耳声发射的特性。结果表明：1)正常人耳声发射由两个主回声串和若干次回声组成。主回声序列分为短潜伏期在10毫秒以下的快成分和长潜伏期在10毫秒以上的慢成分。在1.5 kHz以上的较高频段检测到明显的快分量，在1.4 kHz以下的较低频段检测到明显的慢分量。虽然快成分和慢成分都表现出非线性特征，但慢成分的检测阈值相对较低，通常低于OdBnHL，饱和在20-30dBnH.2左右。在突发性耳聋或梅尼埃病的早期，严重听力损失大于50dBHL的耳朵经常可以检测到100 Hz窄带EOAEs。3)在梅尼埃病或突聋早期，慢成分的持续存在预示着听力损失的良好预后。4)在正常耳中表现出的慢成分的非线性特性在病变耳中消失。因此，使用非线性点击序列不能从病理性耳朵中检测到EOAEs。

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.