Binaural beats are a naturally-occurring, acoustic "illusion" that is created when two pure tones of slightly different frequencies are simultaneously introduced into each ear. Like an optical illusion, these two frequencies cause the audio logical processing centers of the brain to make the listener imagine that they are hearing one sound that is fluctuating, vibrating, or "beating"—sort of like the sound you hear when a violinist is putting vibrato onto one note they are playing.

Listening to binaural beats on their own has a limited capacity to modify brainwave states. When combined with pink sound (see question 3), the effect is enhanced considerably. When the brain hears a combination of pink sound and binaural beats, the brain will begin to follow the frequency combination that is being presented to the ears.