本論文以主動式噪音控制(Active Noise Control , ANC)來減低火箭發射瞬間於駕駛室(操控室)所造成的暫態高分貝(達140分貝)噪音。首先，針對火箭發射時所錄製的兩組噪音信號進行時域及頻域分析，藉此瞭解火箭發射噪音的特性。為方便噪音控制演算法之發展及效果評估，製作一全比例尺寸之壓克力駕駛室模型，模擬實際音場。實驗進行時，先以單通道FXLMS噪音控制方法，依循模態控制原理，找出針對駕駛者頭部噪音消音，控制喇叭最佳擺設位置。之後於駕駛室模型內左右兩側前方各放置一個噪音源喇叭以撥放發射噪音，設想火箭發射時大部分噪音由發射室兩側門窗縫隙進入室內；並利用三個控制喇叭產生反相聲波，以主動式噪音控制方式達到降低駕駛者耳部附近噪音目標。研究中採用以「適應性濾波理論」為基礎之演算法—FXLMS作為第二路徑離線鑑別ANC控制方法，第二路徑線上鑑別則採用Eriksson、Bao與Zhang三種單通道線上鑑別方法進行實驗。本論文以多通道FXLMS驗證利用主動噪音控制消除火箭發射噪音的可行性，並比較三種單通道第二路徑線上鑑別與噪音控制的能力。 In the study, an adaptive noise reducer has been designed and fabricated to adaptively reduce deafening noise with transient and non-stationary nature during continual rocket firing. First, we use signal channel FXLMS to test and verify the model control principle, and find out the best location to place control loudspeakers. The “Adaptive filter theory” is the main algorithm we use in this study and the method of off-line identification in secondary path is multi-channel FXLMS. As to on-line identification in secondary path, we utilize three kinds of on-line identification of single channel from Eriksson, Bao and Zhang. This dissertation takes multi-channel FXLMS to know the feasibility of active noise control in reducing rocket-firing noise. We also compare the ability of reducing noise and the three kinds of on-line identification in secondary path. All experiments are conducted in a full-scale PVC model of the control room.
