555 Timer Sound Generator

This sound generator circuit uses the 555 timer IC to produce a monotone sound of 800 Hz that could be used as the basis of an alarm system. In this circuit, we are using the 555 IC in astable configuration to produce a train of rapidly changing square waves. Each square wave will cause the speaker cone to move up and then down (very fast), and therefore it will vibrate rapidly creating sound waves.

The circuit can operate from as little as 5 V up to 15 V supply voltage. Remember that the square wave output (pin 3) will be close to the supply rail voltage; therefore, you will need a suitable loudspeaker that can handle the power. You can place a resistor (R) in series with the speaker to change the loudness, or use a variable resistor to suite your taste. Ideally, the resistance of the speaker plus that of R must total approximately 75 Ω. Once the basic circuit is up and working, it is great to experiment with it by changing the component values and seeing how the sound changes. You could replace the 100 kΩ fixed resistor with a variable one to see how the frequency of the sound changes.