Sounds and ultrasounds can be generated with the circuit shown in the figure. What we have is a counterphase oscillator / amplifier that powers a common high impedance piezoelectric transducer. Some of these transducers, such as those used in tweeters, have a frequency response good enough to reach the ultrasound range up to about 25 kHz. Thus, we have two possibilities of use for the device: using common piezoelectric capsules with lower frequency response, we generate sounds. The potentiometer or trimpot P1 is then adjusted to obtain the highest yield. On the other hand, using a piezoelectric tweeter, from which the internal transformer has been removed and directly connected to the transducer, we reduce the value of C1 and generate ultrasounds. both cases are interesting:
a) sounds
• Warning or alarm systems
• Scare mosquitoes
• Audio generator
b) Ultrasound
• Scare animals (dogs, etc.)
• Dog call
• Generator for physics experiments
