利用單晶片與類比電路設計主動噪音控制系統之研究

Study on Using Microcontroller and Analog Circuits to Design Active Noise Control Systems

何宗穎(Chung-Ying Ho)

指導教授 ： 張政元

中原大學/工學院/電機工程研究所/碩士(2014年)

https://doi.org/10.6840/cycu201400416

摘要

目前市面上有許多主動式降噪的耳機，而在這些產品中可以分為兩類，其中一類是以數位訊號處理器(DSP)作為系統的控制器，並將Feedback FXLM演算法實現在DSP上，另一類則是利用類比電路，透過傳統的回授控制來實現。兩種方法都有其缺點，採用數位訊號處理器的方式，雖然運算速度夠快，但由於處理器本身單價過高，以致產品價格往往遠超過傳統耳機。若是使用類比電路，成本雖然能大幅降低，但在窄頻噪音的消噪能力上，表現就不如數位型架構來的好。
因此本篇論文提出利用單晶片(Micro-controller Unit, MCU)來設計數位型的主動式降噪耳機，將Feedback FXLM演算法實現於控制器上，再結合類比型主動降噪的架構，一方面降低處理器的成本，並保持數位型架構較好的窄頻消噪表現，另一方面利用類比型對於寬頻噪音較好的降噪效果，提出複合式的主動降噪耳機的設計。依據實際的實驗結果，證明本文設計的單晶片數位型主動式降噪耳機，能在低成本的條件下，對於窄頻噪音仍有10~20 dB的降噪能力，在類比型架構中，透過Matlab模擬也可得到寬頻噪音的消噪效果。

關鍵字

主動式降噪耳機 ； 回授控制 ； 窄頻噪音 ； 單晶片

並列摘要

Nowadays, there are many commercial ANC (Active Noise Control) headphones using either digital signal processors (DSPs) as control unit to implement the Feedback FXLMS algorithm, or analog circuit by using control theory’s feedback structure to cancel the noise in active way. However, for DSP’s product, it’s much expensive than conventional passive headphone, and for analog circuit product, it doesn’t perform as well as adaptive one with narrowband noise. As a result, this paper proposed using a micro-controller unit (MCU), Cortex-M4, instead of DSP to implement the adaptive algorithm in headsets, and also designed the controller for analog ANC structure. Experimental results illustrate the digital control ANC headsets’ performance with commercial headset to verify effectiveness. For analog system, the simulation results also show its work with broadband noise. According to the experimental results, the narrowband noise can be reduced about 10~20 dB using the proposed digital ANC system based on a low-cost MCU. The attenuation of broadband noise can also be verified by computer simulation.

並列關鍵字

Active Noise Control headphone ； micro-controller unit (MCU) ； Feedback FXLMS ； narrowband noise

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