複合材料板的聲傳平滑研究

Abstract

本文主要探討複合材料平板之振動特性與揚聲表現，應用振動平板材料組成及不同邊界設計減緩聲壓曲線大幅振盪，使曲線趨於平滑。以有限元素軟體 ANSYS分析平板振動行為，進而比較理論分析與實驗結果，探討聲壓變化的原因，改良結構設計。 結構以PC塑膠與碳纖複材製作平板，邊界則以泡綿彈性懸邊及複材懸臂支承平板；組裝揚聲器進行實驗量測，與理論分析比較驗證後，應用有限元素法模擬分析不同結構設計的振動特性，繪製其聲壓曲線，再由各激振頻率下的振形表現探討聲壓曲線振盪因素，依據分析結果，改變結構的設計，有效提升揚聲效能。

This thesis is focused on the vibration characteristics and the performance of sound pressure level(SPL) of laminated composite panels. The main purpose is to smooth SPL curves using the different material compositions and boundary conditions. The finite element code ANSYS is used to determine the vibration responses of the plates. The sound pressure generated by the plate is computed using the first Rayleigh integral. Experiments are performed to measure the sound pressure generated by a number of plates. Comparing experiment results with theoretical preditions , we study how SPL curves vary. Then we can find out the influence of each design parameter on sound pressure responses of loudspeakers. By summarizing the results , we can improve the design of the radiating panel. PC plastics and carbon composites are used to construct the transparent radiating panels supported by elastic suspensions and composite beams. The radiating panels together with actuators , suspensions , composite beams and panels are used to make speakers which are then tested to study the sound pressure responses of the speakers. After verifying the theoretical analysis by comparing with experiment results , we further use the finite element method to simulate SPL curves of the speakers. Observing the vibrating shapes , we can find out which factor causes the SPL curves to have pits and peaks . Based on this , we can design the structures and improve the performance of their sound pressure responses.