How to choose the right buzzer?

There are many types of bee horns, you need to know several parameters (voltage, current, drive mode, size, connection/fixed method), of course, more importantly, the sound you want to get (sound pressure, frequency),
Working voltage: Magnetic bee bee ringer, from 1.5 to 24V, piezoelectric from 3V to 220V are feasible, but the general voltage is still recommended to have a voltage above 9V to obtain a louder sound.
Current consumption: Electromagnetic type depends on the voltage difference, from tens to hundreds of milliamperes, piezoelectric type saves much power, a few milliamperes can operate normally, and when the buzzer starts, it instantly consumes about three times the current.
Drive mode: Both kinds of buzzers have self-excitation, as long as connected to direct current (DC) can sound, because there is a built-in drive line in the bee horn, because of the different action principle, the electromagnetic buzzer to use 1/2 square wave to drive, piezoelectric square wave, in order to have a better sound output.
Size: The size of the buzzer will affect the volume and frequency, from 7mm to 25mm for electromagnetic type, and from 12mm to 50mm or larger for piezoelectric type.
Connection method: Common pin (DIP), wire (Wire), patch (SMD), piezoelectric large and lock screw method.
Sound pressure: Bee buzzer often 10cm distance as the test standard, the distance doubled, about 6dB attenuation, on the contrary, the distance shortened doubling will increase 6dB, electromagnetic buzzer can reach about 85dB / 10cm level, piezoelectric can do very loud, common alarms, most of them are made of piezoelectric buzzer.