A few loud banging sounds were reported coming from a distance this morning (52509). The events are clearly observed by microphones at 10-50 Hz at every end station (example spectrogram and q-scan attached). They each reached EY first, then CS (0.7s later), then EX (12.2s later), consistent with some people on site reporting that they seemed to be coming from the south. Triangulation using the relative arrival time differences between stations shows that the source of these noises may have been some 8-12km in the minus X direction relative to the corner station. This is the area just northwest of Hammer training center. The last figure shows the triangulation, which is based on the three loud events reported in Corey's log (EY arrival times of 16:15:48.2, 17:16:31.4, and 17:46:22.0 UTC) and shows shaded regions accounting for 0.1s error in delta_t.