测量地表声阻抗率的实验研究

Experimental Study on the Earth Surface Acoustic Impedance Measurement

建立一个声波能量从空气中耦合到地下的实验系统模型。采用音响作为能量源发射扫频的正弦波声信号穿透到地下土壤;用声级计和地震检波器串分别测得地表的声压级和震动速度,画出二者比值即地面声阻抗率的变化曲线,以此分析声/地震波耦合的效率及其影响因素。在给定音响喇叭相对被测地面高度的情况下,地表声阻抗率在73到90Hz这个范围附近出现了极小值。现场实验证明,该系统能有效完成测量任务,可用于地下浅层埋藏物探测的实验室研究。

An experimental model for the coupling of airborne sound into the earth was developed. Loudspeaker was used as energy source to insonify a swept sine tone over the soil. Besides, that the acoustic impedance or ratio of acoustic pressure at the ground surface measured by a sound level meter to the seismic velocity measured by a geophone array was plotted and used to analyze factors affecting the acoustic to seismic coupling. There are minimum peaks in the ratio in the vicinity of 73 and 90 Hz given the height of the speaker. The in situ experiments prove that the measuring system can realize the test efficiently and can be used to experimental study of shallow buried objects detection in soils.