蜗窗激励评价的有限元计算模型研究

EVALUATION OF ROUND WINDOW STIMULATION BY A FE MODEL OF HUMAN AUDITORY PERIPHERY

蜗窗驱动是实现中耳听力装置与耳蜗耦合的新途径.利用外耳道、中耳和耳蜗集成有限元模型,分别模拟外耳道声激励经听骨链、前庭窗传入内耳的正向传递过程和蜗窗机械激励在耳中逆向传递过程,计算获得中耳和耳蜗的传递函数.比较蜗窗激励和外耳道激励下耳蜗基底膜的振动,提出了以基底膜最佳反应部位位移相等为准则的蜗窗等效激励力计算方法.理论计算获得的蜗窗等效激励力与相关文献根据实验数据预测结果一致.计算结果还表明耳蜗窗正、逆向激励时,基底膜上最佳反应部位无变化,但在蜗窗逆向激励耳蜗时,低频下驱动基底膜运动的效率比高频时低.所获得的理论结果可为蜗窗驱动的听力装置设计和现有装置的应用提供参考.

The round window placement of a vibratory transducer is a new approach for coupling an implantable hearing system to the cochlea. To evaluate the vibration transfer to the cochlear fluids and partition in response to normal acoustic stimulation and to mechanical stimulation of the round window, an acoustic- structure coupled finite element （FE） analysis was conducted by utilizing recently developed FE model which consists of the external ear canal, middle ear and cochlea. The middle ear and cochlear transfer functions such as the sound pressure gain across middle ear, intracochlear pressures, as well as basilar membrane vibration, were derived, during normal forward sound stimulation as well as reverse RW stimulation. The present results show that the round window stimulation with a harmonic pressure produces basilar membrane response similar to normal forward sound stimulation. Then a model was proposed to calculate the force required of an actuator at the round window to produce a basilar membrane displacement that is equivalent to a stimulus produced in normal ear by a given external ear-canal pressure. The information is essential for supporting the optimization of the actuators and adapting existing prostheses specifically for round window stimulation in order to insure sufficient acoustic output.