A Study On Acoustic Signal's Pickup By An Experimental Minisize Piezoelectric Ceramic Sensor

Part OneA Screening Test on Piezoelectric Ceramic Bimorph Elements for an Experimental Implantable Sensor in VitroObjective:To screen out minimal piezoelectric ceramic bimorph element (PCBE) to be assembled an implantable sensor which can pick up acoustic signals from the vibration of ossicular chain.And the sensor can act as an implantable microphone for the totally implantable cochlear implant.Material & Methods:In vitro,26 sizes of PCBEs(PT300-10,produced by Pante Electronic Ceramic R&D Center Co.Ltd.,China),0.3mm in thickness, 2.5 mm,2.0 mm,1.5 mm,1.0 mm in width,and 2.0 mm to 8.0 mm in length, which connected with a testing mainboard(including preamplifier system),were tested.A software,Cool Edit Pro 2.1,recorded the output signals picked up by the PCSs(Piezoelectric ceramic sensors),with 44.1 kiloherts sampling rate,16bit sampling precision and single channel in real-time.All output signal files were saved in the type of.wav.To analyze their frequency response curves,ref total harmonic distortion and volt peak-peak of the output signals by the PCBEs,picked up from the pure tone varying from 250 Hz to 8000 Hz.Results:①All tested PCBEs can picked up acoustic signal which frequency response curves were accordant with the pure tone in nine frequencies,②All ref total harmonic distortion＜0.5%,③According to randomized blocks statistical analysis by statistics software,Intercooled Stata 7.0, the PCBEs(1.0 mm in width) could also pick up sound signal just same as other three widths PCBEs.And the shortest size was 2.0 mm.Conclusions:①Ihe PCBEs(PT300-10,produced by Pante Electronic Ceramic R&D Center Co.Ltd.,China) of 2.0-6.0m m in length,1.0 mm in width and 0.3 mm in thickness could be used for assembling piezoelectric ceramic sensors.②And they should be further screened out. Objective: To screen out minimal piezoelectric ceramic sensors (PCS) for an experimental implantable Sensor in vitro. This sensor can be implanted to coupled with the malleus in middle ear.Material & Methods: (1)A series of experimental PCSs (nine pieces), which were assembled with PCBEs and preamplifier LMV1032, were tested in vitro. These sensors had same width (1. 0 mm) and thickness (0. 3mm), but different lengths varying from 2. 0 mm to 6.0 mm. (2) Each PCS was fixed on the standard speaker by adhesive tape. The input acoustic signals included 20 second sweep signal and 40 second music plus speech signal. A software, Cool Edit Pro 2. 1, recorded the output signal, picked up by the PCSs, with 44. 1 kiloherts sampling and single channel in real-time. All output signal files were saved in the type of .wav. The qualitative analysis of the difference from the time-domain waveform and spectrum distribution between the input acoustic signals and output signals picked up by PCSs was performed.Results: (1All tested PCSs can picked up acoustic signal which frequency response curves were accordant with the input acoustic signal. (2) And the shortest PCS, which could pick up an available signal from the input acoustic signal, was 3. 5 mm in vitro.Conclusions: CD All tested PCSs can picked up acoustic signal which frequency response curves were accordant with the input acoustic signal. ?The shortest PCS which can pick up an available acoustic signal was 3. 5 mm. If the limited space of middle ear and the need of ecapsulation of PCSs were taken into account, the PCBEs of 3. 5 mm, 4. 0 mm, 4. 5 mm in length could be used to designed experimental implant microphone. Objective: To screen out a miniature piezoelectric ceramic sensor for the implantable microphone of a experimental totally implant cochlear implant in vitro. And its efficacy of acoustic signal pickup from the malleus in the cat ear was analyzed.Materials and Methods: 1. According to the Part Two of this dissertation, We selected three sizes of miniature piezoelectric ceramic sensors (3. 5 mm, 4.0 mm, 4. 5mm in length), encapsuled with the thin copper crusts which had rectangle shape in cross section (1. 6 mm in width, 1. 3 mm in thickness), and 4.0 mm, 4. 5mm, 5.0 mm in their responding length. The piezoelectric ceramic sensor for one commercial bone-anchored hearing which had been applied in the Part Two of this dissertation, was selected as the positive control in this experiment. 2. The testing acoustic signal included the pure toneCnine frequencies, 250Hz, 500Hz, lOOOHz, 1500Hz, 2000Hz, 3000Hz, 4000Hz, 6000Hz and 8000Hz) , 20 seconds continuous rising sweep signal (20Hz—20KHz) and 40 seconds music & speech signal. The same testing surroundings and recording methods with above experiments was used in this experiment. 3. The statistic analysis was performed to distinguish the differences of the frequency response curves, total resonance distortions and the Volt peak-peak values of responding response of nine frequencies pure tones picked up by the three sensors. 4. The comparative analysis was done to qualitatively study the time domain waveforms and frequency spectrums of their pickups of the sweep signal and music & speech signal0 5. The selective sensor was fastened with the malleus in the 4-0 surgical silk thread in the cat ear. The pickups of the sweep signal and music & speech signal were recorded and qualitatively analyzed. And the synchronous pickups from the same sensor in the middle ear cavity were set up for the control group. 6. The signals picked up from the vibration of the ossicular chain and the testing signal were input into an eight-channel electrode simulator, to demonstrate the stimulating course of cochlear implant, by displaying the distribution of their envelops in the responding stimulated electrode array.Results: 1. The miniature piezoelectric ceramic sensors (3.5 mm, 4.0 mm, 4. 5 mm) can pick up the three type testing acoustic signal. The response frequency of these pickups are in accord with the testing signal, ranging from 20 to 20000Hz. All frequency response curves of these output signal from these three sensors are approximately plain. For nine frequencies responses, each sensor can pick up mildly different volt peak-peak values. 2. Although there is a significant difference of the volt peak to peak values between these three sensors and the commercial sensor compared by random group statistic analysis in the pure tone signal testing, there is no different between the size of 4. 5 mm sensor and the commercial sensor by the statistic analysis for paired data. They two sensors can both pick up acoustic signal sensitively。3. The 4. 5-mm piezoelectric ceramic sensor can sensitively pick up the sweep signal and music & speech signal from the vibration of the ossicular chain in cat. 4. When the pickups and the testing signal were input into the electrode simulator, the special software displays an approximate distribution of the two signal envelops in the electrode array.Conclusion: 1. The three miniature piezoelectric ceramic sensors ( 3. 5 mm, 4. 0 mm, 4. 5 mm) can respond strictly the audible sound in accord with frequence response, ranging from 20 Hz to 20000 Hz. And they are relatively sensitive available to pick up the testing acoustic signal in vitro。The best performance of picking up signal is played by the 4. 5-mm size, which crust is 5. 0 mm in length, 1. 6 mm in width and 1. 3 mm in thickness) in the three sensors.。2. The 4. 5-mm sensor can be implanted into the cat ear and coupled with the malleus of ossicular chain to pick up acoustic signal in a good performance. 3. The pickups can actuate the electrode array to produce electric hearing when they are input into the electrode simulator. It is the feasibility that this experimental miniature piezoelectric ceramic sensor can be used as the implant sensor for the totally implantable cochlear implant.