內支承改裝平板聲輻射之適應性主動控制

Abstract

本文旨在針對四邊固定的矩形均勻平板進行內支承改裝，先破壞其基本共振模態，使其共振頻率偏移，再利用FIR數位濾波器配合LMS適應性演算法做主動式控制，以進一步達到抑制平板輻射聲功率的目的。 研究結果顯示，矩形均勻平板經過內支承改裝再施以適應性主動控制之後，幾乎皆能有效降低平板低頻時各共振模態輻射聲功率達10dB左右，且較僅主動控制或僅內支承改裝多了平均3至5dB的降幅。但306及391Hz僅作主動控制時，效果最佳。533Hz僅作內支承改裝時，效果最佳。

This study is to focus on the refashioning using inner support of square homogeneous plate with fixed ends. To achieve the suppressing of the acoustic power radiation from plate, the fundamental mode is destroyed first to shift the associated resonant frequency. Meanwhile, a FIR filter with LMS algorithm is selected to be the involved control system. The results from study clearly show that refashioning the square homogeneous plate using inner support to combine the adaptive active control can achieve almost 10dB attenuation at low resonant frequencies of acoustic radiation from plate. Otherwise only 5dB attenuation is achieved for either inner support refashioning or active control to be used. Summarily speaking, the best effectiveness for only using active control or inner support will, respectively, exist at 306 or 391 or 533Hz.