單晶片主動降噪耳機之設計與實現

Active Noise Control in Headsets by Using a Microcontroller

李聖庭(Sheng-Ting Li)

指導教授 ： 張政元

中原大學/工學院/電機工程研究所/碩士(2009年)

https://doi.org/10.6840/cycu200900989

摘要

主動式降噪耳機(Headset)利用主動噪音控制(Active Noise Control, ANC)的技術，產生的人為噪音來消除環境噪音；配戴此種ANC耳機不僅可以提升聆聽音樂時的品質，同時並可避免環境噪音對身心造成的傷害。然而，目前市面上的ANC耳機幾乎都是架構在昂貴的數位信號處理器(Digital Signal Processor, DSP)平台上。DSP強大的資料處理能力和高運行速度使ANC耳機的實現變得容易，但伴隨而來的則是不斐的價格，這也是ANC耳機並不普及的原因。因此，本論文的目標希望以單晶片微控制器(Micro-controller Unit, MCU)來取代DSP，實現一低價位ANC耳機。期望藉由低價位的吸引力，來增加消費者的接受度。同時，本論文提出輸出限制(Output-Limit)演算法，這種方法可防止太大的噪音造成MCU運算時的失控，且不會影響系統迭代修正的正確性，故可有效地提高系統穩定性，使MCU設計的ANC耳機有更好的噪音消除能力。由實驗結果可知，本論文所設計的ANC耳機不僅可大幅降低系統造價成本，同時，在消音能力上可消除低頻噪音達90%以上，與市面上高價位的ANC耳機已達相似之功能。

關鍵字

主動噪音控制 ； 降噪耳機 ； 輸出限制演算法 ； 單晶片

並列摘要

The active noise control (ANC) headphone can cancel noise actively in the noisy environment. However, ANC headphones are usually very expensive due to the cores of the ANC headphones are built on a digital signal processor (DSP) platform. This paper tries to use the micro-controller unit (MCU), instead of a DSP, to design a low-cost ANC headphone.
In order to realize the ANC on a MCU, this paper also proposes the Output-Limit feedback filtered-X least mean square (Output-Limit FFXLMS) algorithm. This method can suppress that loud noise which may lead the conventional FFXLMS algorithm to unstable situation. In addition, the stability and convergence rate of Output-Limit FFXLMS algorithm are also discussed and compared with FFXLMS algorithm and feedback filtered-X normalize least mean square (FFXNLMS) algorithm. In the experiments, the proposed MCU based headphone show the superior performance when compared with a commercial leading ANC headphon. The headphone could cancel the undesired low-frequency noise over 90% when the noise range is under 800Hz. The results prove that using a low-cost MCU instead of the DSP still can achieve a successful ANC headphone.

並列關鍵字

Output-Limit FFXLMS ； ANC ； Headphone ； MCU

參考文獻

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