[Video] Ultrasonic Distance Sensors

A piezoelectric transducer is a device which transforms one type of energy to another by taking advantage of the piezoelectric properties of certain crystals or other materials. https://www.bjultrasonic.com/category/ultrasonic-transducer/
When a piezoelectric material is subjected to stress or force, it generates an electrical potential or voltage proportional to the magnitude of the force. This makes the piezoelectric transducer ideal as a converter of mechanical energy or force into electric potential.