Mission Control said it was connected to its hardline audio line and initially could not hear the sounds, but later picked up a " kind of pulsing noise, almost like a sonar ping.

Passive sonar is a listening-only mode. It hears sounds traveling through the water and records data about that sound, like the pitch, frequency, and direction it came from.

A creepy, sonar-like sound coming through Starliner’s speaker posed a brief mystery on the ISS Astronaut Butch Wilmore radioed Mission Control on Saturday for help figuring out the source of a ...

Mission Control at Johnson Space Center, Houston, likens the sound to a 'pulsing noise, almost like a sonar ping' ...

This weekend's sonar-like noises most likely have a benign cause, and Wilmore certainly did not sound frazzled.

Wilmore puts the mic next to Starliner's speaker and the operator describes the sound as "kind of like a pulsing noise, almost like a sonar ping." ...