听骨链振动声学信号拾取与补偿实验研究

发布时间：2018-08-15 12:14

【摘要】： 目的：通过自制微型压电传声器与猫耳内和新鲜颞骨标本内的听骨链耦合,拾取体外声信号,并对声信号进行调节与补偿处理的实验研究,系统验证听骨链振动拾音与补偿策略的可行性。材料与方法：①利用有限元ANSYS软件建立PT300-10型压电陶瓷双晶片单悬臂梁结构振动模型,分析压电陶瓷双晶片的谐振频率。②制作方柱形压电传声器,4.5x1.5x1.2mm与长度5.0x1.5x1.2mm规格各6个,采用粘接于扬声器防风罩上进行压电传声器体外模拟实验。③将压电传声器植入猫耳,分别粘接固定于锤骨、砧骨体,以及单独置放于鼓室腔,共实验13耳(8只猫),拾取纯音、扫频和语频测试信号。并以Hy-M30高保真传声器在猫耳旁对相同信号拾音作为对照组。④将压电传声器植入新鲜颞骨标本,耦合位点分别为锤骨、砧骨短突、鼓室腔,共实验7耳(4副颞骨),也设相同对照组。⑤压电传声器从猫耳锤骨拾取声学信号,对其畸变与丢失进行补偿与调节初步研究。结果：①有限元仿真模型发现压电陶瓷双晶片在单悬臂结构自由振动情况下,3.0xl.0x0.3mm规格时其谐振频率在20kHz附近,即可满足拾取全频段可听见声信号时既有灵敏度又有平坦的频响曲线要求。②体外模拟实验发现质量为38mg(包含12mg导线),体积5.0x1.5x1.2mm的自制压电传声器能灵敏地拾取全频段可听见声声学信号,具有很高的信噪比和平坦的频响曲线,故用于植入实验。③猫耳内植入实验结果提示压电传声器耦合于锤骨柄后能拾取体外声学信号,并能驱动全植入人工耳蜗演示电极阵列系统工作,但是有比较明显的底噪信号,并且1000Hz及以下频率信号损失较严重。对言语频率信号拾取效果良好,猫耳砧骨拾取信号非常微弱。④新鲜颞骨标本植入实验发现压电传声器与锤骨耦合后拾取信号良好,对于低频信号也能拾取到微弱信号,优于猫耳锤骨耦合时拾取信号。耦合于砧骨短突时则拾取信号较弱。⑤颞骨标本植入实验拾取信号优于猫耳植入实验(锤骨组比较,颞骨组拾取信号具有更为平坦的频响曲线,砧骨组比较,颞骨组拾取信号更强)。猫耳听骨链质量(17mg)远小于人耳锤骨(28.4mg),加之自制压电传声器质量(38mg)重于猫耳锤骨两倍,比人耳锤骨重约一半,过重的负载导致了鼓膜听骨链对于测试声源低频信号的振幅显著减弱,从而出现拾取的信号中低频信号明显丢失。⑥对从猫耳锤骨拾取信号进行145-9288Hz带通滤波,再采用WDRC法进行动态增益放大等信号处理,可以补偿拾取信号的大部分损失,进行一定程度上的输出幅值差异化调节。结论：①通过系统实验初步论证了压电传声器拾取听骨链振动声学信号与补偿策略的可行性。②因压电传声器物理尺寸、质量偏大,手工制作等因素,实验数据与实用需求相比尚有较大距离。③由于MEMS技术的进步、压电材料质量的提升,通过持续深入的实验研究,可以改善与缩微压电传声器,研发耦合固件,完善信号补偿与调节处理软件等方面,从而为全植入人工耳蜗体内拾音策略提供良好解决方案。
[Abstract]:Objective: To investigate the feasibility of the auditory ossicular chain vibration pickup and compensation strategy by coupling a self-made piezoelectric microphone with the auditory ossicular chain in cat ears and fresh temporal bone specimens.
MATERIALS AND METHODS: (1) Vibration model of PT300-10 piezoelectric bimorph single cantilever beam was established by finite element ANSYS software to analyze the resonant frequency of piezoelectric bimorph. In vitro simulation experiment, 13 ears (8 cats) were implanted with piezoelectric microphone and fixed in malleus, incus and tympanic cavity respectively. The pure tone, sweep frequency and speech frequency signals were picked up. The same signal was picked up by Hy-M30 high fidelity microphone beside the cat's ear as control group. Seven ears (four pairs of temporal bones) were tested and the same control group was set up. _Piezoelectric microphone picked up acoustic signals from the malleus of the cat ear to compensate and adjust its distortion and loss.
RESULTS: The FEM simulation model showed that the resonant frequency of the piezoelectric bimorph with 3.0xl.0x0.3mm specifications was about 20 kHz under the condition of free vibration of the single cantilever structure, which could satisfy the requirements of both sensitivity and flat frequency response curve when picking up the audible acoustic signals in the full frequency band. The self-made piezoelectric microphone with a volume of 5.0x1.5x1.2mm can sensitively pick up acoustic signals in the whole frequency band. It has a high signal-to-noise ratio and a flat frequency response curve, so it is used for implantation experiment. 3. The results of cat ear implantation experiment indicate that the piezoelectric microphone can pick up external acoustic signals after coupling to the hammer handle, and can drive the whole implant. Cochlear demo electrode array system works, but there is obvious background noise signal, and the frequency signal loss below 1000Hz is serious. The speech frequency signal picking effect is good, cat's ear incus picking up signal is very weak. 4 Fresh temporal bone specimen implantation experiment found that the piezoelectric microphone coupled with malleus picking up signal is good, right The weak signal can also be picked up in the low frequency signal, which is better than that in the cat's ear and malleus. The cat ear ossicular chain (17mg) is much less than the human ear malleus (28.4mg), and the self-made piezoelectric microphone (38mg) is twice as heavy as the cat ear malleus, about half as heavy as the human ear malleus. The overload causes the tympanic ossicular chain to significantly weaken the amplitude of the low-frequency signal for testing the sound source, resulting in the pickup signal of the low-frequency signal is obvious. Loss. _To the cat ear malleolus pickup signal 145-9288Hz band-pass filtering, and then using WDRC dynamic gain amplification signal processing, can compensate for most of the pickup signal loss, to a certain extent, the output amplitude difference adjustment.
CONCLUSION: The feasibility of picking up acoustic signals and compensating strategies of ossicular chain vibration by piezoelectric microphone is preliminarily demonstrated through systematic experiments. The experimental data are far from the practical requirements because of the factors such as physical size, large mass and handmade. Through continuous and in-depth experimental research, we can improve and micropiezoelectric microphone, develop coupling firmware, perfect signal compensation and adjustment processing software and so on, so as to provide a good solution for cochlear implant sound pickup strategy.
【学位授予单位】：复旦大学
【学位级别】：博士
【学位授予年份】：2010
【分类号】：R764

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