| Summary: | 碩士 === 國立交通大學 === 電機資訊國際學程 === 107 === The objective of this thesis is to study the method to improve the performance of Micro-Electro-Mechanical-Systems (MEMS) loudspeaker which is widely used in the application of the hearing aid and smart phones. For the hearing aid, the miniaturization of loudspeakers is desired to avoid social stigma and to fit inside the ear canal while the sound is easily heard. The geometry of loudspeaker, in particular, the distortion, is also a major concern since it is critical to efficient sound reproduction. Besides, very small loudspeakers are an indispensable unit of smart phones that are today’s universal communication and entertainment devices. Therefore, excellent quality of sound generated by MEMS loudspeaker in smart phone is strongly demanded. Major factors to characterize a loudspeaker are Sound Pressure Level (SPL) and Total Harmonic Distortion (THD). SPL is a factor related to the volume of sound and therefore higher SPL is desired. THD is a factor related to noise and thus lower THD is desired. In other words, we should increase SPL and decrease THD by fine-tuning the detailed design of MEMS loudspeakers. In a typical MEMS loudspeaker, the cone is a membrane film on which a circular coil is attached. A magnetic equipment forces the circular coil to mechanically move by Lorentz force and then the membrane film can be vibrated in response to input signal to the magnetic equipment. The mechanical action of membrane film is sensitive to the radius of the circular coil and thickness of the membrane film. In this thesis, we use a simulator, COMSOL Multiphysics Version 5.3a to improve SPL and THD of a cylindrical MEMS loudspeaker by tuning the radius of the circular coil and thickness of the membrane film. The optimized radius of the circular coil is 775
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