“…③Probe (sensor) layout. Since the rock sample is a cylindrical standard specimen, to pinpoint exactly where the sound originated, probes are arranged in a double-layer surround monitoring network [ 28 ]. The eight probe positions are arranged in a spatial right-angled coordinate system with the centre of the bottom surface of the specimen as the coordinate origin, with the following coordinates: (25, 0, 20), (0, 25, 20), (−25, 0, 20), (0, −25, 20), (25, 0, 80), (0, 25, 80), (−25, 0, 80), (0, −25, 80), the probes 1–4 and 5–8 are arranged respectively under the specimen and on the upper two planes.…”