声速测量实验原理讨论

Discussion of principle of sound speed measurement experiment

对空气中声速测量实验原理进行了讨论,考虑了空气对声波的吸收,分别用平面波和球面波表示发射探头和接收探头之间的声波,导出了接收声压的表达式,分析了声压随探头间距的变化规律.结果表明,尽管声场不是理想驻波,但声压极值随探头间距按半波长周期性的变化规律与驻波共振原理得到的结论相一致,然而3种原理在解释接收声压幅值衰减规律时存在差异,其中球面波原理与实验现象最吻合.

The principle of sound speed measurement in the air is discussed. The sound wave propagation between the ultrasonic emitter and receiver is analyzed on the basis of plane wave method and spherical wave method taking into account the air absorption. The sound pressure on the receiver is derived, the variety of sound pressure with the spacing between the emitter and receiver is dis- cussed. It is showed that strict standing wave is unavailable here, which is a result of the loss of sound energy during propagation. However, it is true that the distance between two adjacent signal maximum is always half of a wavelength. The interpretation of the sound pressure attenuation based on spherical wave method is in accordance with the experimental phenomena.