Astronaut Butch Wilmore reported unexplained sonar-like pulsing noises from the Starliner spacecraft, docked to the ISS. NASA is investigating the cause, which is likely nothing too serious. The incident follows other challenges with Starliner, which is set to return autonomously to Earth on September 6, without its original crew.https://www.notebookcheck.net/NASA-astronaut-reports-strange-sonar-like-noise-from-Boeing-Starliner-docked-at-ISS.882582.0.html
It is the heart beat of a stowaway.