Alternating Current Sound
Électronique / Electronic
NE5532

The circuit in this project allows you to hear alternating current. You probably know that the electric power running through your home is an alternating current.

All your appliances that receive power from electric outlets operate on AC-including lamps. Lamps actually flicker at the rate of 60 times per second, but it looks constant because our eyes see after images.

In this project you will hear sound converted from light. Ready to start?

After building this circuit, turn on the power to your kit by setting the switch to ON. Place the CdS cell near an electric lamp. Can you hear a hissing sound coming from the earphone?

This is the sound of the alternating current. Now place the CdS cell under a fluorescent lamp, and listen for a similar sound. This circuit greatly amplifies the signals of light on the CdS cell through the operational amplifier.

Adjust the quantity of light on the CdS cell with your hand. You can probably hear the volume of the hissing sound reduce and the quality of the sound improve.

See what happens when you expose the CdS to sunlight.