超声波衰减系数的测量讲义及数据

、 目 空气和水中二、原理在损耗介质中准驻效应反射波反射面反射波反射面入射波OX0X1.束在空气中传播和反射产生源处于坐标O，入射束沿坐标x轴方向传播，其动方程为： y expix 入 0反射动方程为：

（1）y =RAexpx2x

（2）反 0 0R为反射k为传播，是介质k

是矢。入射和反射在0～x 区间叠加，其合成动方程为：0 0 0 0 ypx

xpit

2x

eit

Ae

cosRAex2

cosk

2x

iAe

sinRAex2

sink

2x 0 0 0 0 0 0 0 0（3）AA

e2

R2e2xx

2Re2

s2k

xx

4）0 0 0 0:AA0

1Rex

(5)AU

6）A U0 0UU0xU，i则A RxA

i7）A0令 8）yAA

lnUiU0 0bn1R9）

yb

0）、实验过程：2.3.AA0

1RxR。因发生器和接收器由同一材料制成所以有：A UA U0 0UU0xUi if=37120HzT27±1上声形极大时接收换能相应列于表一二。次1距离(mm)11.9(V)次次1距离(mm)11.9(V)次13距离61.50(mm)(V)234567891011129.3814.1218.8123.5828.2833.0331.8242.3147.2352.0856.8411.610.59.688.247.286.725.924.805.325.004.80141516171819202122232466.2570.8975.7080.4484.9989.7894.7199.66104.07108.77113.54.684.684.244.404.003.963.723.003.403.403.24次1距 离(mm)(V)次次1距 离(mm)(V)次11距 离(mm)234567891016182022.5252729.531331.331.311.311.171．201.020.880.7680.704121314151617181920384042444649515355电(V)压0.60.520.540.530.440.520．480.520.510.50次数21222324252627282930距(mm)离57606264666870727477电(V)压0.500.500.480.480.490.460.490.490.500.49（1）测的衰减系数。3.超声波在空气中的衰减率拟合曲线4.2。表三：调整空气）12345678距离(mm)4.649.3814.1218.8123.5828.2833.0331.82电压(V)11.911.610.59.688.247.286.725.921314151617181920距离(mm)61.5066.2570.8975.7080.4484.9989.7894.71电压(V)4.804.684.684.244.404.003.963.72表四：调整1314151617181920距离(mm)4042444649515355电压(V)0.540.530.440.520．480.520.510.502324252627282930距离(mm)6264666870727477电压(V)0.480.480.490.460.490.490.500.495.6.、结果分析：的=0.01dB/mm，与文献所述的结果相比偏小，而所测得的=17.04dB/m，与文献所述结果相比则偏大；剔除掉, 0.02, 1.44m。气 水、设计性开设设想：8，下试析对声波影响7414室四台电脑EXCEL让老师检查如离正确，要做确正确。第次课：一种介质试老师检查声衰对两次课要做析声波：波法声速非完全波学物理2001,14(2)：9～10张庆李卓凡王小怀定物52～房晓勇及,物1～lO19U0

V率f

z=2m。接着方波分别方不同占空比下幅度与应位置坐标再比较两现方锯齿时与。表格1234512345678mm4.699.2414.0618.8323.6728.4233.2638.01V31.426.823.019.215.613.712.411.9910111213141516mm42.9047.6652.3557.1261.9367.1371.4476.23V10.29.88.647.67.046.566.46.3（占30%方作发射信号）次数12345678（mm）4.389.1513.9418.6723.4628.2733.0537.81电压（V）32.4025.8019.6019.0015.0013.0011.8010.80次数910111213141516（mm）42.6647.3552.1056.8361.6066.2571.1175.88电压（V）9.528.007.126.806.005.845.485.36（50%方波作发射信号）次数12345678（mm）4.399.1613.9318.7423.5028.3233.1437.83电压（V）40.0031.6027.6023.6018.2015.8015.1013.30次数910111213141516（mm）42.6047.2952.0656.8461.6166.2171.1075.88电压（V）11.8010.609.528.407.507.126.906.80（70%方波作发射信号）次数12345678（mm）4.269.1514.0418.7223.5228.3033.0437.85电压（V）32.0026.6021.2019.2015.1013.0011.9010.30次数910111213141516（mm）42.6147.3451.9356.7761.5866.2771.0275.94电压（V）9.848.246.966.806.125.845.525.08中的衰减系数（锯齿作发射信号）次数12345678（mm）4.399.1914.0418.7123.5128.2933.1137.88电压（V）25.2020.8018.2014.0011.9010.009.047.80次数910111213141516（mm）42.5347.2452.0156.7861.6366.3270.9975.77电压（V）7.506.645.965.164.524.524.284.2010.005m10.005m）1.9V）23