利用相位補償技術實現主動降噪

Implementation of Active Noise Cancellation Using Phase Compensation Technology

駱榮欽(Rong-Chin Lo) ； 何進益(Chin-Yi He) ； 戴志遠(Chih-Yuan Tai)

《臺北科技大學學報》 45卷1期 (2012/09) Pp. 23-29

https://doi.org/10.29768/JNTUT.201209.0003

摘要

利用嵌入式電路或類比電路等系統來有效降低噪音的分貝值，直至目前為止仍然是一件艱難的工作。尤其在開放式環境，混合複雜頻率的噪音和排油煙機的風切聲，產生3D擾流噪音源，對於固定電路系統、喇叭單體、麥克風、降噪機構等，產生不同的相位偏移，其降噪效果不易控制與提昇。本文以主動降噪技術的研究發展為主，實現排油煙機的降噪功能。首先，將排油煙機的噪音源作快速傅立葉轉換，分析噪音源的頻譜分佈。其次，在整套降噪系統中，分成降噪機構和主動降噪電路，並裝設在排油煙機內作為降噪用途。3D擾流噪音源本身有不同成分的頻率訊號，且對於系統的各部份，各有其不同的相位偏移，不易補償消除。因此，事先運用降噪機構將3D噪音源控制成近似1D噪音源，再量測整套系統的相位特性，建立主要頻率的相位偏移的記錄表，藉由相位偏移量設計對應的相位補償電路。在開始主動降噪時，將排油煙機的1D噪音源經由麥克風收音，相位補償電路將噪音中不同頻率的訊號作定量的相位補償，反相後由擴大器電路傳送到喇叭產生反相訊號。因為相互抵消波形，反相訊號和噪音源產生破壞性干涉，達到降低噪音分貝值的效果。

關鍵字

主動降噪 ； 相位補償 ； 破壞性干涉

並列摘要

Using the embedded systems or the analog circuits to reduce the noise effectively, it is a difficult work until now. Especially in the open environment, there are the 3D disturbed noise with complex frequency and the wind noise of exhaust hood, and the phase offsets induced from the fixed circuit system, speaker, microphone and noise reduction mechanism. So, the effect of lower noise is not easy to control and to improve. In the paper, we will focus on the research of active noise cancellation and implement the function of noise cancellation for exhaust hood. First, we use FFT to calculate the spectrum of the noise sources. Second, in the whole noise cancellation system, they are divided into noise cancellation mechanisms and active noise cancellation circuits. It is useful to reduce the noises when equipping them with an exhaust hood. The 3D disturbed noise sources are composed of different frequencies and different phase offsets. It is not easy to compensate and eliminate. Therefore, firstly, we control the noise sources from 3D into near 1D by using the suitable mechanisms, and then measure the phase characteristic of the whole system. After this, the phase offsets for main frequencies are recorded into one table, and then, the corresponding phase compensation circuit by the table is designed. When active noise cancellation system starts to work, the 1D noises of exhaust hood are recorded by a microphone, and then the phases are compensated by the circuits. To compensate the phases, the signals with inverse phase are transmitted from an amplifier to the speaker to cancel the noise sources. Due to the inverse phase noise signals producing a destructive interference with the original noise sources, the goal to decrease the decibel value of the nose is achieved.

並列關鍵字

Active noise cancellation ； Phase compensation ； Destructive interference