Acoustic Beats

When two sounds with nearly identical frequencies are produced at the same time, the sound waves interfere with each other in a surprising way. The result is a regular, pronounced ‘woo woo’ or beat sound. Adding a third sound with a nearly identical frequency causes an even more complex interference pattern.

Note: The graphs on the right have been slowed down so you can see the difference.

• Press a button to listen to the tone it produces.
• Press again to mute the sound.
• Press two different buttons to sound two tones together. Listen to the interference beats that result.
• Press all three buttons together and listen to the interference pattern.