Studies of cochlear mechanics: otoacoustic emissions

描述（由申请人提供）：正常的耳朵不仅检测，而且产生声音。这些内耳产生的声音，即，耳声发射，可以使用耳道中的微型麦克风来测量。在众多的耳声发射中，立方畸变产物耳声发射（DPOAE）已被广泛应用于婴儿听力筛查、听力障碍的诊断和监测以及听力机制的研究。人们普遍认为DPOAE是由沿耳蜗分区从顶端到底部沿着反向传播的行波引起的。处于主频率f1和f2的行波在它们的重叠区域中相互作用，并且产生处于2f 1-f2频率的声能，该声能沿沿着耳蜗分区在两个方向上传播。后向行波传播到镫骨和耳道，并以相对较短的延迟作为发射的分量出现。前向行波传播到2f 1-f2 CF位点，在那里它被部分反射并形成第二后向行波，这产生具有长延迟的发射分量。在耳道中测量的发射是长延迟分量和短延迟分量的总和。然而，由于缺乏直接测量行波在敏感耳蜗中的传播方向的实验手段，所提出的反向传播行波尚未得到证实。本研究利用新近研制的激光扫描干涉显微镜进行以下实验：1）测量2f 1-f2发射频率下基底膜振动的纵向模式、波传播方向和速度，2）观察f2 CF部位附近耳蜗分区振动与镫骨振动在发射频率下的时间关系; 3）测量电诱发基底膜振动的波传播方向和速度，以测试耳蜗内声源是否诱发反向行波。本研究的结果将促进我们对耳声发射如何在耳蜗中传输的理解，提高临床耳声发射测试结果的解释，并有助于耳蜗力学的一般问题。

DESCRIPTION (provided by applicant): The normal ear not only detects but also generates sounds. These inner ear-generated sounds, i.e., otoacoustic emissions, can be measured using a tiny microphone in the ear canal. Among the various otoacoustic emissions, the cubic distortion product otoacoustic emission (DPOAE) has been widely used for infant hearing screening, the diagnosis and monitoring of hearing disorders, and for studying hearing mechanisms. It is widely believed that the DPOAE results from a reverse-propagating traveling wave along the cochlear partition from apex to base. Traveling waves at primary frequencies f1 and f2 interact in their overlap region and create acoustical energy at the 2f1-f2 frequencies, which propagates in both directions along the cochlear partition. The backward-traveling wave propagates to the stapes and the ear canal and appears as a component of the emissions with a relatively short delay. The forward-traveling wave propagates to the 2f1-f2 CF sites, where it is partially reflected and forms a second backward-traveling wave, which generates an emission component with a long delay. The emission measured in the ear canal is the sum of the long and short delay components. However, the proposed reverse-propagating traveling wave has not yet been demonstrated due to the lack of experimental means to directly measure the propagation direction of the traveling wave in sensitive cochleae. Using a recently developed scanning laser interferometer microscope, the following experiments will be conducted in this study: 1) measurement of the longitudinal pattern and the wave propagation direction and speed of the basilar membrane vibration at the emission frequency of 2f1-f2; 2) observation of the time relationship between the cochlear partition vibration near the f2 CF site and the stapes vibration at the emission frequency; 3) measurement of the wave propagation direction and speed of electrically evoked basilar membrane vibration to test if an introcochlear acoustic source induces a backward traveling wave. Findings of this study will advance our understanding on how the otoacoustic emission is transmitted in the cochlea, improve the interpretation of clinical otoacoustic emission test results, and contribute to general issues of cochlear mechanics.