Most people get a lot of information from their environment from passive sonar...how "echoey" a room is, for example. People can take this ability much further.

Most people get a lot of information from their environment from passive sonar...how "echoey" a room is, for example. People can take this ability much further. https://www.youtube.com/watch?v=uH0aihGWB8U https://www.youtube.com/watch?v=uH0aihGWB8U