具加勁揚聲板之最佳化設計

Abstract

具加勁揚聲板之最佳化設計

研究生：游政霖 指導教授：金大仁 博士

國立交通大學機械工程研究所 摘要

本文首先探討不同彈性支承及板的剛性對複合材料揚聲板之聲壓曲線的影響，其中分別利用波浪型與L型的支承來製作揚聲器，由所量得的聲壓曲線得知彈性支承對本文所討論的揚聲板的聲壓並無太大影響，但板的剛性卻對中音谷的發生有重要的影響，故本文在改善中音谷的方法為使用複合材料來加勁振動板。板在振動時，不良的振形會導致在某些頻段下，聲壓的輸出產生落差。本文應用驗證過的ANSYS有限元素模型對揚聲板作分析，並找出這些不良的振形。在這些變型量較大的振形上採取加勁的方式，並利用最佳化設計方法設計加勁條的尺寸以抑制板的變形，同時考慮不同設計模型，藉加上權重函數並在維持一定的聲壓感度下，求出適當的加勁條大小，使揚聲器能有更好的聲壓曲線表現。本文亦用實驗驗證所提設計方法的可行性。

Optimum Design of Stiffened Composite Sound Radiating Panels Student : Cheng-Lin Yu Advisor : Dr. Tai-Yan Kam

Department of Mechanical Engineering National Chiao Tung University

ABSTRACT

In this thesis, the first part studies the effects of elastic suspensions and panel rigidity on the sound pressure level (SPL) curves of composite sound radiating panels. The SPL curves measured by the used of wave-type suspensions and L-type suspensions in loudspeakers have shown that these effects are minimal. But, the effects of panel rigidity are too significant to be neglected. In order to improve the smoothness of SPL curve, composite stiffeners are added to the radiating plate to suppress the mid-frequency dip of the SPL curve. In the theoretical study, some mode shapes of the radiating plate that may have adverse influences on the sound radiation in certain frequency ranges are determined using a verified ANSYS FEA model. An optimal design method is proposed to determine the dimensions of the stiffeners for different stiffening patterns. For each stiffening pattern, the optimal stiffener sizes are determined to suppress the detrimental modes which are harmful to sound radiation and make the SPL curve smoother and the speaker possess higher sensitivity. Experiments are performed to verify the feasibility of the proposed design of the loudspeaker.