Piezo Buzzer vs Piezo Transducer
A Piezo Buzzer will output a continuous tone when the rated DC voltage is applied to its terminals. The Piezo Buzzer contains an internal oscillator to produce a typical 1-2 KHz tone. A Piezo Transducer is really a speaker that requires an audio oscillating tone be applied to its terminals to produce a sound. No sound will be produced when a DC voltage is applied.