We can use Arduino to make many interactive works of which the most commonly used is acoustic-optic display. All the previous experiment has something to do with the LED. However, the circuit in this experiment can produce sound. Normally, the experiment is done with a buzzer or a speaker. The buzzer is simpler and easier to use. The buzzer we introduced here is a passive buzzer. It cannot be actuated by itself, but by external pulse frequencies. Different frequencies produce different sounds. We can use Araduino to code the melody of a song, which is actually quite simple. Specification: 1. Working voltage: 3.3~5V; 2. Interface type: digital; 3. Weight: 5g.