Buzzers are commonly used as piezo buzzers and magnetic buzzers. Compared to piezo buzzers (12~220 V,<20 mA), the magnetic buzzer operates at lower voltages and higher currents (1.5 to 12 V, > 20 mA). Piezo buzzers typically have a greater maximum sound pressure level (SPL) than magnetic buzzers.In a magnetic buzzer, a current is driven through a coil of wire which produces a magnetic field. A flexible ferromagnetic disk is attracted to the coil when the current is present and returns to a "rest" position when the current is not flowing through the coil. The sound from a magnetic buzzer is produced by the movement of the ferromagnetic disk in a similar manner to how the cone in a speaker produces sound. A magnetic buzzer is a current driven device, but the power source is typically a voltage. The current through the coil is determined by the applied voltage and the impedance of the coil
