北京郵電大學(xué)國際學(xué)院大物實(shí)驗(yàn)聲速wsh

1、Measuring the speed of sound in Air聲速的測(cè)量物理實(shí)驗(yàn)中心Sound WaveSound wave:The propagation of mechanical oscillation in elastic materials. Sound wave is a longitudinal wave.Sound wave 20-20000 HzUltrasonic wave: f 20000 HzInfrasonic wave: f 2 cmSource: receiverReceiver signal: maximumPhase method 相位法沿傳播方向上的

2、任何兩點(diǎn)，其振動(dòng)狀態(tài)相同（相位差為2的整數(shù)倍）時(shí)，兩點(diǎn)間的距離應(yīng)等于波長的整數(shù)倍，即:(1)Travelling wave method 行波比較法Key points:Source: transmitterTransmitter signal: movelessReceiver signal: moveable(2) Lissajous patterns method 李薩如圖法Lissajous patterns method (x-y mode) : 李薩如圖法返回.聲速測(cè)量儀讀數(shù)裝置壓電陶瓷換能器底座返回piezoelectric ceramic transducer Digital-

3、Display-Displacement-Sensor The inherent frequency(固有頻率) of the piezoelectric ceramic transducer is around 40kHz. Then adjust the frequency of the signal generator around 40kHz to maximize the output of receiving transducer，which indicates that the transducers are in resonance 下一頁P(yáng)iezoelectric ceramic transducer 諧振頻率的調(diào)整改變信號(hào)發(fā)生器的頻率時(shí)，看到接收端信號(hào)Experimental contents and procedure用示波器觀察接收器輸出的電信號(hào)，并調(diào)節(jié)出壓電陶瓷的諧振頻率振幅法測(cè)波長求聲速相位法測(cè)波長求聲速 （1）行波比較法 （2）利薩如圖法采用逐差法處理數(shù)據(jù)的詳細(xì)步驟：（1）將測(cè)量列按次序分為高低兩組 （2）取對(duì)應(yīng)項(xiàng)的差值后再求平均： 其中, 為6個(gè)峰值間的距離，即:n123456789101112xix1x2x3x4x5x6x7x8x9x10 x11x12例如，用行波法測(cè)量聲波波長的以下一列數(shù)據(jù)：(3