| Summary: | 碩士 === 國立臺灣大學 === 工程科學及海洋工程學研究所 === 100 === In this thesis, the use of the finite element method is to simulate the micro-speaker and then calculate the sound pressure level of the speaker system. First, this study investigates how the voice coil positions impact on the overall sound pressure. The improved design of diaphragm is hoping to reduce the first eigen frequency and elevate the second modal frequency to increase the overall sound pressure and that the overall sound pressure can also be more stable.
Through the discussion to the position of the voice coil, the radius size of the voice coil has great influence to the sound pressure level. Basically, the speaker’s second mode shape can be divided into voice coil inside and outside diaphragm vibration. With this reason, the investigation of the diaphragm material will base on these two cases and find out the way to improve the efficiency of the speaker by changing the membrane material. In this thesis, after simulation by software, it is found that when the second mode shape is in motion as voice coil inside diaphragm, it is easier to improve the design by changing the diaphragm’s material, due to the first and second mode shape are in different positions of motion. That means the spacing between first and second frequency can be elevated by replacing the material of the voice coil inside and outside. So we will use this model when discussing the thickness of diaphragm, and will get the result that the first eigen frequency will proportional to the thickness of diaphragm.
The finite element method is more efficient and accurate than the electro-mechano-acoustic analogous circuits, although the finite element method has larger amount of calculation, but could effectively describe the high frequency portion and well improved the overall accuracy of the speaker system.
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