Young Darrin J, Zurcher Mark A, Trang Tung, Megerian Cliff A, Ko Wen H
Department of Electrical and Computer Engineering, University of Utah, 50 S. Central Campus Dr., Room 3280, Salt Lake City, UT 84112, USA.
Ear Nose Throat J. 2010 Jan;89(1):21-6.
We propose the use of a microelectromechanical system (MEMS) accelerometer as a middle ear microphone for future totally implantable cochlear prostheses. The MEMS accelerometer would be attached to the umbo to detect and convert the natural bone vibration that occurs in response to external sounds into an electrical signal that represents the acoustic information. The signal could be further processed to stimulate cochlear implant electrodes. To determine the feasibility of our proposal, we conducted a study to investigate whether the characteristics of umbo vibration along two orthogonal axes-one axis being perpendicular to the tympanic membrane and the other axis being parallel to the tympanic membrane plane but orthogonal to the long process of the malleus-differ significantly enough to compromise the sensing performance of the proposed accelerometer should a position misalignment occur during the implant procedure. We used laser Doppler vibrometry to measure the displacement of the umbo along the two orthogonal axes in 4 cadaveric temporal bones at multiple frequencies within the audible spectrum. We found that the peak-to-peak displacement frequency response along both axes was nearly flat from 250 Hz to 1 kHz, and it gradually rolled off with a slope of approximately -20 dB and -40 dB per decade above 1 kHz and 4 kHz, respectively. At each frequency, the displacement exhibited a linear function of the input sound level with a slope of 20 dB per decade. A comparison of measurements along the two axes indicated a similar frequency response, with an average amplitude difference of 20%. The characterization data suggest that the performance of a miniature ossicular vibration-sensing device attached on the umbo would not be degraded in the event of a position misalignment. The data also indicate that a MEMS accelerometer needs to achieve a resolution of 35 i g/sqrt[Hz] to detect normal conversation.
我们提议将微机电系统（MEMS）加速度计用作中耳麦克风，用于未来的全植入式人工耳蜗。MEMS加速度计将附着于鼓膜脐部，以检测并将响应外部声音而产生的自然骨振动转换为代表声学信息的电信号。该信号可进一步处理以刺激人工耳蜗电极。为确定我们提议的可行性，我们开展了一项研究，以调查沿两个正交轴（一个轴垂直于鼓膜，另一个轴平行于鼓膜平面但垂直于锤骨长突）的鼓膜脐部振动特性是否存在显著差异，以至于在植入过程中出现位置未对准时会影响所提议加速度计的传感性能。我们使用激光多普勒振动测量法在4个尸体颞骨中，于可听频谱内的多个频率下测量鼓膜脐部沿两个正交轴的位移。我们发现，沿两个轴的峰峰值位移频率响应在250 Hz至1 kHz范围内几乎是平坦的，并且在1 kHz和4 kHz以上分别以每十倍频程约-20 dB和-40 dB的斜率逐渐下降。在每个频率下，位移呈现出输入声级的线性函数，斜率为每十倍频程20 dB。沿两个轴的测量结果比较表明频率响应相似，平均幅度差为20%。表征数据表明，附着在鼓膜脐部的微型听小骨振动传感装置在位置未对准时其性能不会降低。数据还表明，MEMS加速度计需要达到35 i g/√[Hz]的分辨率才能检测正常对话。
