How to produce ultrasound wave? A: negative piezoelectric effect of transducer B: Piezoelectric effect of transducer C: Thermal effect of transducer D: The magnetic effect of transducer

The operation of and design approaches to mechanical and piezoelectric(压电的) electric wave filters(滤波器) are discussed.

A<br/>piezoelectric crystal is used to produce the ultrasound waves. What<br/>kind of ultrasound is produced? () A: Pressure<br/>wave ultrasound B: Electrical<br/>wave ultrasound C: Sound<br/>wave ultrasound D: Simple<br/>ultrasound