管路之適應性噪音消除

Abstract

本文提出了一套有效消除管路噪音的新方法.傳統的被動式噪音消除系統 是以聲學阻抗不連續的原理來降低管路噪音.本文提出的管路之適應性噪 音消除系統則著重在研發適用於一維聲場的電子消音設備.亦即主動式之 噪音消除器,本法利用人為產生的噪音去抵消原有的噪音信號;此一新的方 法在低頻尤為有效.本控制器主要是以數位信號處理的技術來設計,而控制 方法則分為兩類,第一類為前授式控制法;此法須先做系統判別的工作.第 二類為適應性控制法為利用最小均方法之適應性控制.由實驗結果可知,藉 著本控制器的研發將上述幾種控制理論,配合軟硬體的設計,實施在此一極 具工業應用潛力的主題上,是非常具有機電整合的實際意義的. There is a new method of noise cancellation proposed in this thesis. The study of adaptive ducts noise cancellation focuses on the development of electric noise cancelling equipment to adapt to one-dimension acoustic field such as the ventilative duct of air condition, the exhaust pipe of engine and the opening for ventilation of dust-collecting equipment. This new method is to make use of artificial noise to cancel the original noisy signal, that is, the active noise cancellation, which is different from the traditional passive noise control like the muffler of car or motorcycle. This new method is effective especially in low frequency. This controller is designed for the skill of discrete-time signal processing. And the method of control is devided into two types. The first one is feedforward control. Before the commence of this type, the work of system identification must be finished. The second one is adaptive control, which is to make use of the lest-mean- square method. From the result of this experiment, it's very clear to see that by means of the research of controller to apply these control theories above to the topic of practical industrial application is very meaningful.