場域式主動噪音控制之開發與應用

本論文以數位訊號處理器(Digital Signal Processor, DSP)為基礎，將主動噪音控制技術(Active Noise Control, ANC)應用於座椅頭枕上，並根據使用環境的不同提出合適的方法，以達到場域式降噪的目的。車輛行駛所產生的噪音對人耳來說是一項無形的損害，本文介紹了在車輛座椅的頭枕上使用帶有編程增益放大器(PGA)的 ANC 系統，解決車內多變的交通噪音問題。在實際應用中，汽車的行駛速度並不總是恆定的，當車速不規則變化時，麥克風接收到的噪音增益必須相應改變，從而影響 ANC 效果。因此，提出了將增益維持在理想範圍內的 PGA 技術，以結合前饋式結構和最小均方(LMS)算法來消除頭枕上的交通噪音。在廠辦的環境中，除了需要考量環境中不同的噪音源種類之外，根據使用者位置的不同，實驗設置上也需要進行相應的調整，其中麥克風的設置為本文中主要探討的項目之一，根據噪音源的來向與場域的限制提出合理的擺放位置。除了主動式噪音控制之外，我們結合被動式噪音控制(Passive Noise Control, PNC)設計，將環境中高頻噪音降低，從而使廠辦內的降噪效益達到最佳化處理。

關鍵字

主動噪音控制；數位信號處理器；可編成增益放大器；頭枕；能量估測方法

並列摘要

Based on the digital signal processor (DSP), this thesis presents using the active noise control technology (ANC) on the headrest and proposes a suitable method according to the different environments to achieve the purpose of field noise reduction. The noise generated by the driving of the vehicle is an invisible damage to the ear. This paper describes the use of an ANC system with programming gain amplifier (PGA) on headrest of vehicle to solve the problem of variable traffic noise. However, in practice, the driving speed of the car isn’t always constant, and when the speed of the vehicle changes irregularly, the gain of the noise received by the microphone must be changed accordingly, thereby affecting the ANC results. Therefore, the PGA technique is proposed to maintain the gain within the ideal range to combine with the feedforward structure with the least mean square (LMS) algorithm to cancel the traffic noise on the headrest. In a factory office, in addition to considering the different types of noise sources, the experimental setup also needs to be adjusted according to the user's location. The microphone setting is one of the items discussed in this article. Propose a reasonable placement position according to the direction of the noise source and the limitation of the field. In addition to active noise control, we use passive noise control (Passive Noise Control, PNC) design to reduce highfrequency noise in the environment, so as to optimize the noise reduction in the factory office.