我們製作了一個音準練習程式:使用者輸入聲音後,經由音頻辨識方法求出其頻譜中最高振幅之頻率,以之為音高,再將其與目標音高相較,得到其誤差率及走音程度。此外還可發出對應的鋼琴及正弦波的聲音,方便使用者校音。文中說明音頻辨識的方法,一些關於音樂的基本知識,微軟公司的wave 檔格式,及此系統之應用。我們使用FFT 辨識頻率,且將針對此部分演算法做簡單的說明,並探討如何達到所需之頻率準確度,及如何以較高效率辨識。目前誤差率已可達到1Hz 以下,判斷時間也在秒之內。儘管國內外也有一些具備相似功能之音樂編曲軟體,但其功能十分繁複,使用者常需花費數週時間學習,且價格常高至數千元,非一般使用者所能負荷。而這個程式不但使用方便,功能簡單,容易上手,且不需任何費用。We have developed a singing-practicing program: after input the sound, we judge its pitch from the corresponding spectrum; then we compare it with the selected one, and output the deviation, so that the users can see if they had been out of tune. Also, we provide the sound of the piano and the sine wave sound of the chosen pitch, which can help users get the right pitch. This report will briefly introduce the method of pitch recognition, some basics of music, and Microsoft's wave file format. In addition, we explain the application of this program. We use FFT to transform a sound wave into the spectrum, which are briefly explained in the article, too. Also we’ll discuss how to improve the accuracy and efficiency of the transformation. So far the deviation is less than one Hertz, and the recognition takes less than one second. Though there have been some commercial software with similar functions, they are often complicated to use, and cost a lot. This is not affordable to most users. On the contrary, our program is not only convenient and easy to use, but also has a simple user interface. What’s more, it costs no money!
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冷熱生電-熱電效應之席貝克效應(Seebeck effect)
席貝克效應〈Seebeck effect〉是熱能與電能之間的一種固態能量轉換方式,當兩種不同性質的金屬導線之端點連接形成封閉迴路時,若兩接點間有溫差,則兩接點間可測得電壓,而因單位溫差所產生的電壓差稱為席貝克係數〈Seebeck coefficient〉。由本實驗的結果發現:溫差大小、導線特性〈熱電係數〉、導線表面有無氧化層是影響席貝克效應中電壓值及席貝克係數大小的原因。溫差越大,電壓值越大。鉑〈Pt〉與其他金屬的熱電偶導線組合之熱電轉換效能為Pt-Fe > Pt-C > Pt-Al > Pt-Sn;導線的表層若有氧化層,會造成電壓在上升過程中穩定性不佳,產生高低起伏的跳動溫壓曲線,但在較高溫差時,溫壓曲線趨於穩定上升狀態。The Seebeck effect is one of thermoelectric effect. A voltage existed between two ends of different metal wires when a temperature gradient existed between the two junctions. This means the conversion of temperature differences directly into electricity. The voltage induced was called electromotive force, EMF. The EMF generated was dependent on the properties of the wires, which formed the thermocouple and the temperature difference between the junctions. This paper was to study the effect of variety of wire combinations and geomtric properties of wires in thermocouple on the Seebeck coefficient generated. The results indicated that temperature difference, wire properties, and absence or presence of oxidative layer on the surface of wires were the factors to affect the magnitude of voltage and the Seebeck coefficient. As the temperature difference between the junctions was increased, the voltage increased. The combination effiency of conversion of temperature difference into electricity of platinum was following: Pt-Fe > Pt-C > Pt-Al > Pt-Sn. The presence of oxidative layer on the surface of wires caused instability during the process of voltage increase. It made the temperature-voltage curve up and down. On the contrary, when the temperature difference was big, the temperature-voltage curve became increased stably. The temperature-voltage curve was independent of geomtric properties of wires.
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