Piezoelectric buzzers feature low power consumption, lack a magnet, and have no additional EMI/EMC concerns. A buzzer is comprised of an ultra thin piezoelectric ceramic (5), bonded to a vibrating metal disk (4). When a voltage is applied, the piezoelectric ceramic and metal disk vibrate as one component, with the piezo ceramic physically flexing with respect to voltage. The metal disk acts as a diaphragm producing air pressure waves that the human ear interprets as sound. When referring to the chart at the bottom right, this rated 4KHz buzzer will produce optimal output when allowed to vibrate at its resonant frequency. The intensity of the sound is measured in dBs (decibels), which is the measure of sound pressure and, as mentioned previously, is measured at a distance of 10cm. The SPL can be effected by how much voltage is used to drive the buzzer (the higher the voltage, the higher the SPL).