Article: "But to their surprise, the scientists also picked up other sounds in the channel. “There’s infrasound events of unknown nature that occur several times per hour,” says Daniel Bowman, a geophysicist at Sandia and collaborator on the project. “And there’s no good explanation.”

This could help sort out those worldwide "hum" problems ('Taos Hum','Windsor Hum'. [https://en.wikipedia.org/wiki/The_Hum]