複合材料板在不同密閉空間之揚聲行為研究

Abstract

本文重點分兩部份，第一部份為平面揚聲器的構造以及分析方法說明，其中平面揚聲器的構造包括揚聲板的製作、支承材料的幾何形狀、支承結構的製作、以及整體製作的詳細說明。在分析方面，從有限元素的選擇、系統參數的測量、整體模型的建立以及聲壓計算，都有詳細的說明。第二部份則是研究密閉以及半密閉空間(音箱)對揚聲器揚聲行為所造成的影響。音箱的設計有相當多種，我們就最常見的三種：密閉形音箱、低音回復形音箱、以及被動輻射形音箱等三種，本文對音箱設計做詳細的說明，並探討傳統錐盆揚聲器音箱設計公式是否可適用於平面揚聲器音箱的設計。由於探討後發現平面揚聲器音箱經由公式計算出的設計值與實際值有著相當大的落差，故在使用傳統公式時可能只能作為參考而不能完全依公式來做設計。另外亦做了許多不同音箱設計的實驗來觀察其聲音及聲壓曲線的變化，找出對聲音影響最好的設計方式。在音箱種類上經由實驗可發現後斜式被動輻射形音箱對低音表現有最顯著的加強效果。

Two parts are discussed in this thesis. The first part is about the fabrication and analysis of flat-panel loudspeaker. The speaker fabrication includes the design and fabrication of the composite flat-panel, the determination of geometrical shapes of the elastic supports, and the assembling of the parts. In the theoretical study, we discussed the choice of the finite element types, the determination of system parameters, and analysis of the loudspeaker’s sound pressure level (SPL) curve. The second part is to study the sound radiation characteristics of the loudspeaker when it is installed in a closed or semi-hermetic box. There are different designs of the box. We will discuss three kinds of boxes which are commonly used. They are closed-box, the bass reflex box and the passive-radiators box. And then we will investigate experimentally if the box design methods for cone-loudspeaker can be used to design the flat-panel loudspeaker box. We have found the values between the theory and the experiment may be so different that the design methods of cone-loudspeaker box can only be used as a reference. In addition, we also do several different designs to observe the changes of sounds and SPL curve, and try to find the best way to improve them. From our experiment we find that among the different box designs the back oblique passive-radiator box is the most effective one in enhancing bass.