Super Buzzer

(Saftey first! Wear ear protection when working with noise.)

These are really sweet. When properly driven at around 20V, they're absolutely piercing. Seriously. These little devils can do about 90dB at 1m at 18.3V, 36mA (658.8mW). That would be an enormous 20 hours of runtime on just a pair of series-connected 9V batts! Seriously, seriously cool.

This is one of the louder buzzers I've used. At a buck or two per unit, they're dirt cheap, as well. Just... be careful.