This is a project of a 555 buzzer circuit. NE555 is a timer IC comes in 8 pin dip package, it performs wide variety of tasks in electronic circuits. The circuit mentioned below will produce a buzzer sound when 9 volt power will be applied. The frequency of sound can be changed with the help of 1K variable
resistor and changing the value of 15K resistor. All electrolytic capacitors will be of 10 volt ratings, use 8 to 25 ohms speaker. There are also other circuits which you can use for buzzer purpose like 555 tone generator and siren circuit.