The sound wave tube is the channel through which the probe enters the interior of the pile during ultrasonic testing of cast-in-place piles. It is an essential part of the ultrasonic testing system for cast-in-place piles, and its embedding method within the pile and its arrangement in the pile's cross-section directly affect the test results. Therefore, the layout and embedding method of the sound wave tube should be marked on the drawings during the design phase, and the quality of embedding should be strictly controlled during construction to ensure the smooth progress of the testing work.

The selection of spiral acoustic probe materials is based on the principle of high sound transmission rate, ease of installation, and low cost. Sound pulses are emitted from the transmitter transducer, passing through the coupling water to the interface between water and the acoustic probe wall, then through the wall to the interface between the probe wall and concrete. After passing through the concrete, they must pass through two interfaces of another acoustic probe to reach the receiver transducer.