本研究試著建立一套數學模型,分析管線震動,並且將漏水聲波之音訊利用短時傅利葉轉換(Short Time Fourier Transform, STFT)、小波轉換(Wavelet Transform)和Matlab程式的相關性分析(Correlation)建立「中心輻射量測法」,找出漏水點與該地區無漏水點之間音波的頻率關係;接著將中心輻射量測法配合Visual Basic 6.0開發出一套可攜式系統--「NTFL測漏1號」,能夠隨時記錄漏水地點座標、漏水量大小之情形,並可經VB與Matlab接口編程(Serial Port),將資料送至運算處理較強的Matlab做後處理。 本實驗在台北自來水事業處所提供之測漏訓練場進行方法驗證,測得該地區無漏水之特徵頻率在435∼445Hz附近,而漏水點之特徵頻率出現在較高的530∼560Hz附近,和一般測漏員判斷漏水之經驗相同,得到相當可靠之結果。 本研究之價值在於提供一項客觀的測漏方法,排除人為與環境變素,利用數學模型與理論驗證,使得測漏的工作能夠建立一個更加科學化、合理化的可靠系統。而本研究發展的訊號相關性比對法,日後亦可以應用在溫泉區的源頭偵測或是焚化爐中的燃燒聲學上,發揮其他研究價值。
Today, locating leakage is still needs to listend the leakage sound wave by ear via leakage detect instrument. It depends on the experience of trained inspector. This paper tries to analyze the viberation of water pipe by dinamic modle, and develops a method that combined short time Fourier transform (STFT) and wavelet transform with cross correlation to find the relationship between leakage and non-leakage area wave called“Center radiation measure method”. From this experiment could find that the characteristic frequency of non-leakage was distrubiting over 435∼445Hz and leakage characteristic frequency was over 530∼560Hz at test field. The characteristic frequency was usually higher than basic frequency. It corresponds to the experimental result in this paper. Besides, this paper develops a user interface by Visual Basic 6.0 (VB6) named“NTFL Leakage Detector NO.1”. It intergrates GPS, GIS and leakage databank which can record the situation of leakage and location on time into the system. It could send wave files to MATLAB by add programming serial port of VB6 to Matlab. Thus, the task of leakage detection would be more scientific, reasonable, and precise.