多通道主動噪音控制系統設計與實作

本論文以數位訊號處理器(Digital Signal Processor, DSP)應用於主動噪音控制(Active Noise Control, ANC)技術，實際使用多通道演算法應用於汽車安全座椅以及通風管。汽車行駛在路上產生的噪音對成人來說是可以接受的範圍，但對於嬰幼兒會造成聽力損害， WHO 在2018 年的兒童安全聽力會議上提出車廂內音量70dBA 時為嬰幼兒聽力安全的最低容許噪音值，而實際量測車速在100km/hr 時分貝計顯示音量落在70~72dBA 間，剛好在最低標準，若加上主動噪音控制技術便能得到更好的降噪效果。由於車內噪音來自任何方向無法針對單一噪音源處理，因此實驗上除了基本前饋式、混合式演算法驗證，又以多通道前饋式、混合式為主要探討方向，並嘗試處理實際低頻噪音問題。通風管實驗中使用真實通風管做為實驗設置，本實驗考慮風的干擾以及大管徑的靜音區建立，在演算法上使用單通道前饋式、單通道混合式還使用多通道系統實驗，其目的是為了增加靜音區。除了主動噪音控制之外通風管內部設有被動噪音控制(Passive Noise Control, PNC)箱，原理是使用吸音材料、硬體設計的方式降噪，但這只能夠將中高頻噪音降低，因此本實驗結合主被動噪音控制系統對通風管噪音進行控制。

關鍵字

主動噪音控制；數位信號處理器；靜音區；汽車噪音；工業噪音；安全座椅；通風管

並列摘要

This thesis uses the digital signal processor (DSP) to implement active noise control (ANC) techniques for car seat and air duct. The noise made by cars on the road is acceptable for adults, but it can cause hearing damage to infants. According to 2018 Children's Safety Hearing Conference proposed from WHO, the minimum allowable noise level is 70dBA. When measuring the cabin noise in a car with speed 100km/hr, the sound level falls within 70-72dBA, which just meets the minimum requirement. If the ANC technology can be included, a better noise reduction can be expected. Because the noise in a car cabin is not unidirectional, the thesis discusses the multi-channel feedforward and hybrid ANC systems in addition to the basic feedforward and hybrid ANC algorithms. The low-frequency noise problem is studied, too. A practical air ventilation duct, composed by passive noise control (PNC) and ANC parts, is also evaluated by experiments. Several experiments are tested with the consideration of wind disturbance to reduce narrowband and broadband noises to get a large zone of quiet. The algorithm uses not only single-channel feedforward and hybrid ANC systems, but also applies the multi-channel feedforward and hybrid ANC systems to examine the effectiveness of noise reduction. The purpose is to use PNC reducing high frequency noise and use ANC designs to constrain the remaining low-frequency noise.