That's the only way they can get around. All they do is squeek and if the sound bounces back, they know that there's a wall in front of them. They can even judge the distance to the wall. A transmitter , particularly a radio transmitter, can send sounds all over the place. It's sort of like a telephone because it changes electrical impulses into radio waves.
Radio receivers can pick up the waves and then back into sound they go.
Each one is music is a different musical note. If you put all of these together and arrange them low to high or high to low, you have a musical scale. They all make sound by making the air vibrate. Like brass instruments, you play a recorder by changing the length of the piping by pushing down keys or covering up to holes.