為了避免系統因為過熱造成損毀,藉由散熱系統的配置,盡可能地降低環境工作溫度,安裝系統散熱風扇,增加空氣對流並帶走熱氣以降低溫度,但卻因此而產生了惱人的噪音,尤其以個人用電腦以及伺服器機房的風扇噪音最為明顯;傳統在風扇噪音的改善,主要從風扇葉型與風切對流的設計著手,近年來隨著主動式噪音控制(Active Noise Control, ANC)技術的成熟,也有不少相關應用出現,而在風扇的噪音的處理上,也很適合主動式噪音控制技術的使用。 本論文針對散熱風扇,利用數位訊號處理器 (Digital Signal Processer, DSP)實現Feedback ANC 演算法;在不同的實驗環境下,分析風扇在全域下的降噪效果;根據實驗結果,驗證主動噪音控制應用於風扇系統的全域噪音消除有5-15 dB 的降噪能力,平均噪音消除能力也有6 dB 以上。
The fans are commonly used in personal computers (PC) and server systems for decreasing the temperature. The mission of the fan is bringing the hot flow out and taking the cool flow in, so the temperature of whole system could be stable. But it also produces noise. The traditional noise reduction technique is using passive noise control based method or focusing on the design of fan’s blade to reduce the noise. Nowadays, the active noise control (ANC) is a mature technique for the development of high speed processer, it’s suitable to implement ANC on fan system to reduce the noise. This paper proposes using the digital signal processer (DSP) to realize the Filtered-X least mean squares (FXLMS) ANC algorithm to achieve the global cancellation of the fan noise. The experiment results show the performance can be around 5-15 dB using ANC system at different environments with the optimization system coefficients.