旋轉機具廣泛地出現在我們的生活當中,這些旋轉機具使用的時間越來越長,在長時間的運轉下若缺乏保養可能造成旋轉機具的損壞甚至是停擺,如何得知旋轉機具的健康狀況變成了一門重要的課題。 散熱風扇為旋轉機具中相當常見之一類,因此本論文之研究對象為風扇所產生之噪音,由於風扇所產生出來的噪音分為兩種,第一種為氣動力噪音,第二種為結構震動噪音。其中氣動力噪音又包含窄頻噪音和寬頻噪音,本論文使用德州儀器所生產的數位訊號處理器搭配麥克風來量測風扇所產生之噪音,並在數位訊號處理器上實現預測濾波器以分離出風扇之窄頻噪音並抑制寬頻噪音,再透過FFT得到窄頻噪音的頻率與振幅大小,來當作判斷風扇健康狀況之依據,由此來得知風扇是否處在異常狀態,以達到對風扇做監測之目的。 本論文不但對風扇做監測也以後饋主動式噪音控制將風扇所發出之窄頻噪音有效地消除。
Rotary machines is widely applied in modern society, the usage time of rotary machines become longer, and it's a must to do machine maintenance after a long-term operation, otherwise it might lead to machine malfunction or out of order. Cooling fan is a common rotary machine. In this study we focus on the study of noises cause by cooling fan. There are two different types of noise that caused by cooling fan, the first is airborne noise, another is structure borne noise, also the airborne noise including broadband noise and narrowband noise. In the study, I use Texas Instruments DSP with microphone to pick up noise, and implement prediction filter on the DSP to separate narrowband noise from broadband noise then use FFT to get the noise frequency and the magnitude of narrowband noise from cooling fan in order to monitor the status of the cooling fan. In this study not only monitor the status of cooling, but also reduce narrowband noise from the cooling fan by implement feedback active noise control on the DSP.