Hit one of the pipes hanging on the stand. Listen to the sound it makes. Stop the vibration with your hand. Do the same with another pipe. The two emit sounds with slightly different pitches. Quickly hit one pipe after another. You will hear the sound cyclically growing and decreasing in intensity – this is called Binaural Beats.
How it works
Soundwaves can merge. The new wave has properties that depend on the parameters of the component waves. When waves with similar but not identical frequencies are combined, you can hear binaural beats whose intensity varies cyclically between a minimum and a maximum value.