Ultrasonic transducers are piezoelectric ceramics that resonate at ultrasonic frequencies and convert electrical signals into mechanical vibrations by the piezoelectric effect of the material. When the transducer is used as a transmitter, the electrical oscillating signal sent from the excitation source will cause a change in the electric or magnetic field in the electrical energy storage element of the transducer, which changes the mechanical vibration system of the transducer through some effect. A driving force is generated to cause it to vibrate, thereby propelling the medium in contact with the mechanical vibration system of the transducer to vibrate and radiate sound waves into the medium.