There is no need for a current-limiting R (as for an LED). You could verify this with a DMM: Connect the buzzer to a DC supply with the DMM in series, set to a current range.

But there are really just the two speeds with the current programming. Inside the cool laser-cut box is an Arduino Uno and a 9V battery, plus a current-limiting resistor and the all-important buzzer.

Posted in Arduino Hacks, Games, LED Hacks Tagged arcade, arduino, led, lighting effect, pwm Bucky Glow: Have A Ball While You Practice Coding ...