臺灣博碩士論文加值系統

本文主要針對一四邊固定平板之運動與其輻射聲功率間的機制，作基本概念介紹，並概括地說明輻射模態的概念，與體速度相消的控制方法，在實驗方面，首先針對體速度相消法之可控制性進行驗證。其後，則利用遠場麥克風作為平板淨體速度感測器，並結合FIR數位濾波器與LMS演算法，針對壓電片激振平板產生的輻射聲功率，與一單頻迴響聲場所引致之穿透聲功率，進行適應性控制。
研究結果顯示，利用體速度相消控制技術，使平板之淨體速度為零，的確能使其輻射聲功率下降。其次針對在平板振動聲輻射的適應性控制實驗過程中發現，當壓電片之激振頻率為132Hz、178Hz、240Hz、350Hz時，輻射聲功率皆能有效的被控制，其中聲功率最大更可衰減10dB左右；至於在平板聲穿透的適應性控制中，平板的隔音性能在132Hz時可提升6dB，其次在178Hz與240Hz亦有4~5dB之效果，但於400Hz以上之較高頻率時，則仍無法達到控

This study is mainly to introduce the basic concept on the mechanism between the motion of a plate with 4 edges clamped and the sound power radiation from it. Meanwhile, this study also outlines both the concept of radiation modes and the active control technique by using volume velocity cancellation. Therefore, this study is first in experiment to evaluate the control performance when using volume velocity cancellation technique. Later on, we use a far-field microphone as a sensor for the measurement of the net volume velocity of a plate. Combining it with a FIR filter and LMS algorithm, we can make an adaptive control of both the sound power radiated from a plate excited by PZT and the transmitted acoustic power through the same plate acted on by a reverberation sound field in progress.
The result of this study shows using volume velocity cancellation technique to make the net volume velocity of a plate be zero can really reduce the acoustic power radiated from it. Next, we can find from the result in the experiment of adaptive control on the sound radiation from a vibrating plate that the acoustic radiation from a plate can be effectively controlled when PZT is respectively excited at 132, 178, 240, and 350 Hz. Within them, the greatest attenuation by 10 decibels of acoustic power is reached. Regarding the experiment of adaptive control on the sound transmission through a plate, the most sound insulation performance by 6 decibels at 132 Hz can be obtained. Furthermore, 4~5 decibels of sound insulation performance at 178 and 240 Hz are also reached. However, no control effectiveness can be reached when the frequency involved is higher than 400 Hz.

摘 要 I
目 錄 III
圖目錄V
符 號 說 明IX
第一章 緒論1
1.1 前言1
1.2 研究目的與研究方法4
第二章 板振動與聲輻射基本理論5
2.1 平板的動態分析5
2.2 平板的輻射聲功率9
2.3 輻射模態與輻射效率 13
2.4 體速度與遠場聲壓的關係19
第三章 主動控制基本理論模式21
3.1 理論引導21
3.2 數位系統與數位濾波器22
3.3 LMS演算法26
第四章 實驗佈置與實驗方法29
4.1 實驗佈置29
4.2 體速度相消控制之實驗方法 33
4.3 適應性主動控制系統實驗介紹37
4.4 聲輻射適應性控制之實驗方法43
4.5 聲穿透適應性控制之實驗方法47
第五章 結果與討論51
5.1 平板分析與體速度相消控制之結果51
5.2 適應性聲輻射控制之結果59
5.3 適應性聲穿透控制之結果75
第六章 結論與未來研究方向91
參考文獻93

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