There are a lot of processes in place to make Alvin safe for humans. But we have a lot of safety measures in place so it will meet a certification standard set by the U.S. Navy. An instrument in the sphere with a microphone generates an electric signal which goes to a transformer to become higher voltage. It then goes to a piezoelectric element which generates an electrical signal that goes to a speaker. A piezoelectric element on the ship picks up the pressure waves coming from inside Alvin.