Research On Piezoelectric Bone-conduction Hearing Device

In recent years, A bone conduction technology had already rapid developmented. which was first used by the U.S. military equipment.Now,there are bone-conduction cell phone for deafers in the civilian. Listening to use bone conduction technology has many advantages,because bone conduction instead of sending the sound out through the earmold.the singnal travels through a wire leading to a piezoelectric oscillator,which vibrates .the sound vibration is carried through the skull bone to both inner ears. The biggest advantage is bone conduction full released and opened your ears. You can also hear the voices around,and you needn't take away bone conduction oscillator to communicate. You can also use ear plugs to prevent hearing damage noise. Piezoelectric bone conduction hearing device is applicable to many occasions. You can use them in water, and other special circumstances. In the noisy environment can provide clear audio receive. Can be used in strong magnetic field. which is electromagnetic bone conduction hearing device can not be duplicated.A piezoelectric bone conduction oscillator is different from a conventional earphone, fully released and opened your ears.when you communicate, you can hear voices of the environment around.The dissertation research on bone conduction piezoelectric oscillator size,resonance frequency and mechanical quality factor to improve piezoelectric oscillator effect of acoustic. Research on how to overcome the high resonant frequency and high mechanical quality factor to improve bone conduction of acoustic effect. The full dissertation is divided into six chapters, mainly as follows:1.PerfaceThe dissertation have explained the reasons for bone conduction phenomena, which fetch out the concept of bone conduction . And expatiated the bone conduction technology application and development prospects.Two ways of bone conduction oscillator: electromagnetic and piezoelectric.Comparsion and analysis of their advantages and disadvantages,however,expound the piezoelectric bone conduction research meaning.Research focus on bone conduction piezoelectric oscillator.2.The basic character of bone conduction Piezoelectric materials Based on the reverse piezoelectric effect of the piezoelectric materials, Bone conduction piezoelectric oscillator using the audio signal is directly driven and lead mechanical vibration.The sound vibration is carried through the skull bone, and thus the ability to hear sound. piezoelectric vibration components as bone conduction oscillator sound basic components. as well as electrical energy conversion components. Thus the performance of piezoelectric actuators decided bone conduction properties of the acoustic Vibrator. The basic concept of the piezoelectric effect, the basic physical properties of the piezoelectric material and the important performance parameters, including electrical and mechanical coupling coefficient, piezoelectric constant, constant frequency and mechanical quality factor were studied. The electromechanic conversion mechanisms about piezoelectric materials were explained. The vibration modes, the equivalent circuit resonance characteristics were analyzed. The theory on the basis of piezoelectric actuators was expounded. 3. Theoretical research on bone conduction sound vibration piezoelectric oscillator.Theoretical research on the production of piezoelectric oscillator and principle of vibration magnification. Established mathematical models and equations of motion.Analyzing and discussed to reduce resonance frequency of several ways: Increase the length or diameter of bone conduction piezoelectric oscillator to reduce the resonance frequency of the piezoelectric oscillator, Reduce the bending modulus of piezoelectric oscillator to reduce the resonance frequency of the piezoelectric oscillator, Increase the quality of abdominal piezoelectric oscillator to reduce the resonance frequency of the piezoelectric oscillator, Covered with soft materials onto the piezoelectric oscillator to reduce the resonance frequency of the piezoelectric oscillator. Analyzed and discussed the feasibility of each method one by one,how to overcome the high resonance frequency to improve bone conduction sound vibration piezoelectric oscillator of sound effects provided theoretical basis.4. Experimental research on bone conduction sound vibration piezoelectric oscillator.By experimental research on how to reduce resonant frequency of piezoelectric oscillator. Consequently ,bone conduction piezoelectric oscillator can reproduction so full voice.Using HP4294A precise impedance analysis to measure impedance characteristics of different shapes and sizes of the piezoelectric oscillator. The experimental results are compared. Experimental research on the resonance frequency of bone conduction piezoelectric oscillator with the relationship the thickness of soft material coverage. Experimental elected the best values of soft material thickness, Using the TES-1358 real-time audio analyzer to experimental research on acoustic effect of bone conduction piezoelectric oscillator covering 3mm soft material ,which is driven a number of different frequency square wave signal.5. Experimental research on different ways of support on bone condution piezoelectric oscillator.Experimental research on ways to improve bone conduction the acoustic effects of Piezoelectric oscillator :1. Produce an experimental prototype, Experimental research on acoustic effects of bone condution piezoelectric oscillator through increasing the quality abdominal of piezoelectric oscillator and covering silicone material in piezoelectric oscillator together. TES-1358 real-time audio analyzer measurements sound pressure level of bone condution piezoelectric oscillator. By comparing the experimental curve, acoustic effects of bone conduction piezoelectric oscillator be improved, minimum resonance frequency f0c is reduced.Makes low-frequency region voice abundant reappearance,curve become smooth.2.Produce bone conduction piezoelectric oscillator and improve the acoustic effects of Piezoelectric oscillator through covering soft material conducted sound vibration to skull bone. TES-1358 real-time audio analyzer measurements sound pressure level of bone condution piezoelectric oscillator,which is driven by the different frequency. Drawing frequency and sound pressure curve,Compare and analysis the curve, make up for the high-ear loudness of the voices in the low-frequency region. Curve of middle-high frequency region become smoothness, sound makes people feel more melodious.6. ConclusionThe main conclusion of the paper was given, The research prospects for bone conduction piezoelectric hearing device were discussed, and the future research directions were given.