Automatic knocking detection device, system and method for cavity behind tunnel vault wall

The invention provides an automatic knocking detection device, system and method for a cavity behind a tunnel vault wall, and belongs to the technical field of tunnel detection. The rotating motor is fixedly connected with the top end of the telescopic arm, the output end of the rotating motor is connected with the bearing platform through the rotating end, the vibration exciter is connected with the bearing platform and connected with the vibration excitation head through the second telescopic rod, the audio collector is connected with the audio transmitter, and the audio transmitter is connected with the bearing platform. The audio transmitter is used for being in wired or wireless communication connection with the processing terminal, so that the processing terminal carries out tunnel vault wall rear cavity identification according to the received audio data; the method is large in detection range, high in detection speed, high in accuracy and high in stability, can effectively avoid high-altitude operatio