 The probe is an ultrasonic sensor , generally known as a transducer , which functions to send and receive acoustic energy . The emission is generated on piezoelectric crystals by the piezoelectric effect . The reflected ultrasound is received by the probe , transformed into an electric impulse as voltage and sent to the engine for signal processing and conversion to an image on the screen . The depth reached by the ultrasound beam is dependent on the frequency of the probe used . The higher the frequency the lesser the depth reached . 
