Choi Yong-Sun, Lee Soo-Young, Parham Kourosh, Neely Stephen T, Kim Duck O
Brain Science Research Center and Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea.
J Acoust Soc Am. 2008 May;123(5):2651-69. doi: 10.1121/1.2902184.
An efficient method for measuring stimulus-frequency otoacoustic emissions (SFOAEs) was developed incorporating (1) stimulus with swept frequency or level and (2) the digital heterodyne analysis. SFOAEs were measured for 550-1450 Hz and stimulus levels of 32-62 dB sound pressure level in eight normal human adults. The mean level, number of peaks, frequency spacing between peaks, phase change, and energy-weighted group delays of SFOAEs were determined. Salient features of the human SFOAEs were stimulated with an active cochlear model containing spatially low-pass filtered irregularity in the impedance. An objective fitting procedure yielded an optimal set of model parameters where, with decreasing stimulus level, the amount of cochlear amplification and the base amplitude of the irregularity increased while the spatial low-pass cutoff and the slope of the spatial low-pass filter decreased. The characteristics of the human cochlea were inferred with the model. In the model, an SFOAE consisted of a long-delay component originating from irregularity in a traveling-wave peak region and a short-delay component originating from irregularity in regions remote from the peak. The results of this study should be useful both for understanding cochlear function and for developing a clinical method of assessing cochlear status.
开发了一种测量刺激频率耳声发射（SFOAE）的有效方法，该方法结合了：（1）扫频或扫级刺激；（2）数字外差分析。对8名正常成年人在550 - 1450赫兹以及32 - 62分贝声压级的刺激水平下测量了SFOAE。确定了SFOAE的平均水平、峰值数量、峰值之间的频率间隔、相位变化以及能量加权群延迟。用一个在阻抗中包含空间低通滤波不规则性的有源耳蜗模型刺激了人类SFOAE的显著特征。一个客观拟合程序产生了一组最优的模型参数，随着刺激水平降低，耳蜗放大量和不规则性的基波幅度增加，而空间低通截止频率和空间低通滤波器的斜率降低。用该模型推断了人类耳蜗的特征。在该模型中，SFOAE由一个源自行波峰值区域不规则性的长延迟分量和一个源自远离峰值区域不规则性的短延迟分量组成。这项研究的结果对于理解耳蜗功能以及开发评估耳蜗状态的临床方法都应该是有用的。
