This very simple circuit just uses a couple of resistors, a capacitor and the easily available 555 timer IC.
The 555 is setup as an astable multi-vibrator operating at a frequency of about 1kHz that produces a shrill noise when switched on. The frequency can be changed by varying the 10K resistor.There are many variation on electronic applications using 555 timer IC.
For manual data sheet, you can download at www.fairchildsemi.com/ds/LM/LM555.pdf (fairchild semicon)

simplebuzzer01
source : electronic-circuits-diagrams.com