具彈性支撐複合材料疊層平板之振動與聲傳研究

Abstract

本文利用不同分析方法建立模擬具彈性支撐複合材料疊層平板受電磁式音圈激振之振動與聲傳研究，探討複合材料疊層平板之頻率響應模態振形對聲傳聲壓影響，改善聲壓值的起伏落差，提高聲壓曲線的平滑度和提昇聲音的品質。研究中利用有限單元套裝軟體ANSYS與數值法Rayleigh- Ritz method二種方法模擬分析複合材料疊層平板的振動及頻率響應。在揚聲器模型簡化分析中發現音圈會影響分析結果，故於有限元單元建立模型中以薄殼元素建立平板與音圈進行模擬；數值法分析中利用古典板理論分析平板並以簡支梁理論做為加勁模擬音圈，二種分析方法皆應用Rayliegh第一積分式計算聲壓，以獲得平板的聲壓位準曲線。由理論分析結果與聲壓量測試驗所得結果作比較，驗證分析方法的正確性。利用本法對聲壓感度落差較大的頻率進行探討，了解其發生的原因，並改變有關參數，以利提高聲壓曲線平滑度及避免音谷的發生。

In this dissertation, different techniques are proposed to simulate the sound radiation of flexibly supported laminated composite plates. The effects of mode shapes of the plates on the sound radiation of several panel-speakers are investigated and discussed. The design of the panel is studied to eliminate the sound valleys and enhance the smoothness of the sound pressure level (SPL) curves and sound quality of panel-form speakers. In this study the ANSYS software and Rayleigh-Ritz method are used to simulate the plate vibration and frequency responses of several flat-panel speakers. In the proposed finite element model, the thin-shell elements are used to simulate the plate and voice coil. In the Ritz method, the classical plate theory is used to simulate the plate and the simple beam theory used to simulate the coil. The Rayleigh first integral is used to predict the SPL curves of the plates. The simulations of the speaker with different mathematical models show that the coil properties can affect the vibro-acoustic results. The experimental SPL curves have been used to validate the suitability and accuracy of the present method in predicting the SPL curves of the plates. The proposed methods are then used to study the causes for inducing the large SPL valleys and seek the means for reducing the magnitudes of such SPL valleys.