Studies of cochlear mechanics: otoacoustic emissions

描述(申请人提供)：正常的耳朵不仅能探测到声音，还能发出声音。这些由内耳产生的声音，即耳声发射，可以使用耳道中的微型麦克风进行测量。在各种耳声发射中，立方失真产物耳声发射(DPOAE)已被广泛应用于婴幼儿听力筛查、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是由耳蜗尖至底部沿耳蜗区反向传播的行波所致。主频f1和f2的行波在它们的重叠区相互作用，并在2f1-f2频率产生声能，该声能沿着耳蜗区沿两个方向传播。后向行波传播到踝骨和耳道，并以相对较短的延迟显示为发射的一个分量。正向行波传播到2f1-f2 CF位，在那里被部分反射，形成第二个反向行波，从而产生一个具有较长延迟的发射分量。在耳道中测得的放音是长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内传播方向的实验手段，所提出的反向传播行波还没有得到验证。利用最新研制的扫描激光干涉显微镜，进行以下实验：1)测量发射频率为2f1-f2的基底膜振动的纵向模式及波的传播方向和速度；2)观察f2频段耳蜗区附近的耳蜗区振动与发射频率处的距骨振动之间的时间关系；3)测量电诱发基底膜振动的波传播方向和速度，以检验耳蜗内声源是否诱发反向行波。本研究的结果将加深我们对耳声发射如何在耳蜗内传递的理解，改善对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.