長型平板之激振位置對聲傳影響之研究

Abstract

本文旨在探討長型平面揚聲器之激振位置對揚聲行為之影響。因應現今電子產品的平面化趨勢，揚聲器有狹長化的設計需求，而傳統圓形激振器受到狹長揚聲板的寬度限制，會有聲壓感度偏低且中音谷落差大等缺點。因此本文主要分為兩部分，第一部分，設計跑道型激震器作為激振輸出，探討激震器之尺寸參數與氣隙磁通密度之收斂關係，使激震器能有效率地使用，最後歸納各尺寸參數之影響，建立完善的磁通資料庫，提供磁通之快速推估方法，以減少大量的電腦分析時間。第二部分，將跑道型激震器運用在三種常用長寬比之狹長板上，利用建立之磁通資料庫，探討激振器尺寸參數與聲壓曲線之關係，以期望得到最高聲壓感度或最低中音谷落差。最後，實作出跑道型激震器系統，經由實驗驗證，此設計準則可改善狹長型揚聲器之中音谷、提高聲壓感度，並搭配激振器外加磁式方法再次提升其聲壓感度。

This thesis aims to investigate the effects of exciting location on the sound radiation behavior of long flat-panel loudspeakers. In response to the current trend of flat electronic products, the speakers need to be long and narrow. When the speaker becomes narrow, the small width of the radiating plate will limit the size of the conventional circular transducer. The sound pressure level (SPL) of the speaker will become low and a major SPL dip in the mid frequency range may be incurred. In this thesis, the contents are divided into two parts. In the first part, a track-shape exciter is designed. The air-gap magnetic flux densities for different dimensions of transducer components are determined to find the optimal exciter design. Next, establish the magnetic flux database to provide a fast magnetic flux estimation method to reduce the large amount of computer time. The second part is about the use of the track-shape transducer to excite plates with different aspect ratios. The optimum transducer parameters for obtaining maximum SPL or minimum major dip in mid frequency range are determined. A number of loudspeakers are fabricated and tested to verify the proposed design procedure. Finally, a set of design guidelines for improving the SPL curves of different long rectangular flat speakers is proposed.