Study On The Piezoelectric Bone Conduction Hearing Device With Three Vibrators

After in-depth analysis on the status in-and-abroad of piezoelectric bone conductionhearing device, this paper developed a three points frequency piezoelectric bone conductionhearing device which based on the theory of bone conduction and the inverse piezoelectriceffect of piezoelectric vibrator, combining the basic knowledge of audiology and basicproperties of piezoelectric materials. And the relevent simulation analysis and experimentalresearch of the hearing device were conducted. The specific contents are as follows:1. Research situation of piezoelectric bone conduction hearing deviceThe number of people with hearing impairment is increasing, while bone conductionhearing devices can relieve pain in some patients effectively. Bone conduction hearingdevice were classificated according to the receiving signal frequency, the wearing way andthe sounding mechanism, and their features and methods of application were compared. Thatpiezoelectric bone conduction hearing device with its unique advantages become a hot topic,so made an in-depth analysis on its domestic and foreign developments. The piezoelectricbone conduction hearing devices are exist in various forms liking headsets, mobile phones,glasses, watches, etc. But the response frequency of the hearing device with a singlepiezoelectric vibrator is narrow, so the idea that three piezoelectric transducer with differentresonance frequencies are used in the same hearing device was proposed.2. Basic theoretical of piezoelectric bone conduction hearing deviceBasic knowledge of audiology and basic theory of piezoelectric materials wereanalyzed in this part. Audiology knowledge concludes the physical properties of sound, thestructure of people’s audiology system and its ability of perception, the degree of hearingloss, and the afferent pathway of sound into inner ear. Piezoelectric materials theories coverspiezoelectric effect, elastic coefficient, piezoelectric constant, electromechanical couplingcoefficient, mechanical quality factor and other characteristics of piezoceramic material; andthe vibration mode, the resonance characteristic, the hysteresis characteristics, theamplitude-frequency characteristics of the piezoelectric vibrator. These studies are thetheoretical foundation of piezoelectric bone conduction hearing device.3. Simulation analysis and experiment on piezoelectric vibratorPiezoelectric vibrator as the core component of the hearing device, related simulationanalysis and experimental were conducted. The working frequency of the three piezoelectricvibrators and their supporting manners were determined. Simulation analysis on the naturalfrequency and the maximum vibration displacement of the piezoelectric oscillator bychanging the substrate’s length and thickness, piezoelectric plate’s length and thickness, andpiezoelectric vibrator’s width. Optimum sizes of three piezoelectric vibrators were electedand the statics, modal and harmonic static simulation on them were investigated. Test on the three piezoelectric vibrate’s waveform responsiveness, the overall deformation ability,voltage-displacement characteristics and amplitude-frequency characteristic.4. Simulation analysis on three points frequency piezoelectric bone conductionhearing device and developed the prototypeSimulation analysis on the hearing device was carried out and a prototype was designed.The static, modal and harmonic response analysis on the piezoelectric oscillators withconduction columns were conducted, after their sizes were adjusted. The modal simulationwas made for the internal structure assembled by three piezoelectric vibrators and comparedwith the deformation modes before assembled. Simulation analysis on the overalldeformation of the hearing device when different signals input it binding to the workingprinciple of1/3frequency divider. The overall structure and parts of hearing device weredesigned before the prototype was made.5. Test on the piezoelectric bone conduction hearing device with three vibratorsThe performance test on the three points frequency piezoelectric bone conductionhearing device was conducted. The test platform was built, impedance characteristic testshows that the resonant frequencies of three piezoelectric vibrator corresponding to theirmaximum reactance values are240.196Hz,540.392Hz,3.25224kHz, respectively. Thehysteresis characteristic and amplitude-frequency characteristic were conducted. Thehysteresis values and the maximum vibration displacements of the three piezoelectricvibrators are8.25%,7.56%,6.97%,86.08μm,9.14μm,1.545μm, respectively, all in theirown working bands. The loudness and noise of the hearing device were conducted. Threepiezoelectric vibrators have the maximum loudness values within their own workingfrequency band, and the noise of middle-low frequency at one meter away is smaller thanambient noise.