以類比濾波器實現主動式噪音控制技術應用於耳機

Active Noise Control Technology for Headphones with Analog Filter

徐威(Wei Hsu)

指導教授 ： 張政元 ； 郭森楙

中原大學/電機資訊學院/電機工程研究所/碩士(2019年)

https://doi.org/10.6840/cycu201900819

摘要

本論文提出利用類比濾波器實現主動噪音控制(Active Noise Control, ANC)技術應用於耳機，以前饋式(Feedforward)主動噪音控制架構為基礎，並解決數位信號處理器(Digital Signal Processor, DSP)運算限制與電子延遲之因果關係(Causality)問題。

本論文藉由導入前饋式FXLMS (Filtered-X Least Mean Square)演算法，計算得出最佳濾波器係數，並且藉由系統鑑別(System Identification)，得到階數較低之類比濾波器，並以雙二階型式之KHN (Kerwin-Huelsman-Newcomb)濾波器串接(Cascade)型式實現類比電路，並且加入音頻集成(Audio Integration)技術保有耳機聽音樂之功能。

實驗結果表明，針對單一方向之白噪音(100Hz到3.2kHz)、錄製的高鐵、大客車、飛機與變電箱之噪音，皆約有10dB至15dB的降噪效果，且加入音樂不會影響降噪能力，降噪計算也不會干擾音質；本論文除探討噪音源方向對降噪的影響外，也比較市售降噪耳機之降噪性能差別。

關鍵字

主動噪音控制 ； 類比濾波器 ； 耳機 ； 系統鑑別 ； 音頻集成

並列摘要

This thesis proposed the application of the analog filter to realize Active Noise Control (ANC) in headphones. The feedforward active noise control structure was used as the basis to solve causality issue between the operational restriction of Digital Signal Processor (DSP) and electronic delay.

By introducing the feedforward FXLMS (Filtered-X Least Mean Square) algorithm, this thesis computed the optimal filter coefficient and used system identification to obtain lower-order analog filters. This is followed by using second-order KHN (Kerwin-Huelsman-Newcomb) filter cascade type to realize analog circuit. Finally, audio integration technology was added to preserve the headphone’s function of listening to music.

The experimental result showed that the product was able to reduce one-directional white noise (100Hz to 3.2kHz) and pre-recorded noises such as noise from high-speed rail, bus, airplane and transformer box by 10dB to 15dB. Furthermore, the addition of music did not affect the noise-canceling ability and the noise-canceling calculation did not interfere with the sound quality. In addition to discussing the effect of directionality of noise on noise-canceling, this thesis also compared the noise-canceling ability of commercial noise-canceling headphones.

並列關鍵字

Active Noise Control ； Analog Filters ； Headphones ； System Identification ； Audio Integration

參考文獻

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