、 目 空氣和水中二、原理在損耗介質(zhì)中準駐效應反射波反射面反射波反射面入射波OX0X1.束在空氣中傳播和反射產(chǎn)生源處于坐標O，入射束沿坐標x軸方向傳播，其動方程為： y expix 入 0反射動方程為：

（1）y =RAexpx2x

（2）反 0 0R為反射k為傳播，是介質(zhì)k

是矢。入射和反射在0～x 區(qū)間疊加，其合成動方程為：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則A RxA

i7）A0令 8）yAA

lnUiU0 0bn1R9）

yb

0）、實驗過程：2.3.AA0

1RxR。因發(fā)生器和接收器由同一材料制成所以有：A UA U0 0UU0xUi if=37120HzT27±1上聲形極大時接收換能相應列于表一二。次1距離(mm)11.9(V)次次1距離(mm)11.9(V)次13距離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 離(mm)(V)次次1距 離(mm)(V)次11距 離(mm)234567891016182022.5252729.531331.331.311.311.171．201.020.880.7680.704121314151617181920384042444649515355電(V)壓0.60.520.540.530.440.520．480.520.510.50次數(shù)21222324252627282930距(mm)離57606264666870727477電(V)壓0.500.500.480.480.490.460.490.490.500.49（1）測的衰減系數(shù)。3.超聲波在空氣中的衰減率擬合曲線4.2。表三：調(diào)整空氣）12345678距離(mm)4.649.3814.1218.8123.5828.2833.0331.82電壓(V)11.911.610.59.688.247.286.725.921314151617181920距離(mm)61.5066.2570.8975.7080.4484.9989.7894.71電壓(V)4.804.684.684.244.404.003.963.72表四：調(diào)整1314151617181920距離(mm)4042444649515355電壓(V)0.540.530.440.520．480.520.510.502324252627282930距離(mm)6264666870727477電壓(V)0.480.480.490.460.490.490.500.495.6.、結果分析：的=0.01dB/mm，與文獻所述的結果相比偏小，而所測得的=17.04dB/m，與文獻所述結果相比則偏大；剔除掉, 0.02, 1.44m。氣 水、設計性開設設想：8，下試析對聲波影響7414室四臺電腦EXCEL讓老師檢查如離正確，要做確正確。第次課：一種介質(zhì)試老師檢查聲衰對兩次課要做析聲波：波法聲速非完全波學物理2001,14(2)：9～10張慶李卓凡王小懷定物52～房曉勇及,物1～lO19U0

V率f

z=2m。接著方波分別方不同占空比下幅度與應位置坐標再比較兩現(xiàn)方鋸齒時與。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%方作發(fā)射信號）次數(shù)12345678（mm）4.389.1513.9418.6723.4628.2733.0537.81電壓（V）32.4025.8019.6019.0015.0013.0011.8010.80次數(shù)910111213141516（mm）42.6647.3552.1056.8361.6066.2571.1175.88電壓（V）9.528.007.126.806.005.845.485.36（50%方波作發(fā)射信號）次數(shù)12345678（mm）4.399.1613.9318.7423.5028.3233.1437.83電壓（V）40.0031.6027.6023.6018.2015.8015.1013.30次數(shù)910111213141516（mm）42.6047.2952.0656.8461.6166.2171.1075.88電壓（V）11.8010.609.528.407.507.126.906.80（70%方波作發(fā)射信號）次數(shù)12345678（mm）4.269.1514.0418.7223.5228.3033.0437.85電壓（V）32.0026.6021.2019.2015.1013.0011.9010.30次數(shù)910111213141516（mm）42.6147.3451.9356.7761.5866.2771.0275.94電壓（V）9.848.246.966.806.125.845.525.08中的衰減系數(shù)（鋸齒作發(fā)射信號）次數(shù)12345678（mm）4.399.1914.0418.7123.5128.2933.1137.88電壓（V）25.2020.8018.2014.0011.9010.009.047.80次數(shù)910111213141516（mm）42.5347.2452.0156.7861.6366.3270.9975.77電壓（V）7.506.645.965.164.524.524.284.2010.005m10.005m）1.9V）23