Please note, Unlike electromagnetic types which has coil, This buzzer does not contains internal driving circuit, so do not expect to just power on and hear something. It needs square wave of 4Khz to drive. The black case provides cavity for resonance and protection.
When compared to low cost electromagnetic type buzzer this piezo consumes only 2mA, while coil type takes 200mA, making this ideal for battery operation. While electromagnetic type is high on EMI, this piezo’s emi noise is very less.