Sonar sound is a type of sound wave technology used to detect objects underwater. It works by sending out sound waves and measuring the time it takes for them to bounce back, allowing the user to determine the distance and size of the object. The term 'sonar sound' is derived from the acronym 'SOund Navigation And Ranging, ' which describes the process of using sound waves to detect objects. The crossword solution 'PING' is a term used to describe the sound made when sonar sound is used.