When the brain hears two different sounds of similar frequencies in each ear, it combines the two tones to create an entirely new one. Considered to be an "audio hallucination," binaural processing is a phenomenon where the brain becomes confused. The brain takes both tones that are received through headphones to produce a completely unique third sound. Although there are some people who consider this manipulation somewhat controversial, others take advantage of the opportunity to trick the mind into being focused, sleepy, energetic or meditative.
How does it work?
For example, if two sounds are played into the ears, one would be at 100 hertz and the other at 108 hertz. Then, a binaural beat of 8 hertz is created, which the brain waves will match. Therefore, an increase in brain waves of 8 hertz takes place. These are called binaural beats, which take place in the superior olivary nucleus, the site of contralateral integration of auditory input. This created auditory beat is more of a theoretical tone, rather than a normal sound that you hear on a daily basis.
Since the brain isn't used to hearing tones that are so similar to one another with such a high rate of intensity, it cannot comprehend them like it would a typical sound. The binaural beat is conveyed in the brain, and then neurotransmitters are used to initiate changes in brain wave activity. The third sound that is created is comprehended by each individual differently, and one person can hear a different sound based on when the binaural beats occur.
What happens when listening to binaural beats?
There are a number of factors that change the way your brain perceives sounds, and it may cause you to feel an altered state of consciousness. The response to binaural-beat stimulation is completely subjective. While external factors play a large role in the response, white noise is also considered to have an influence. For instance, if there is white noise, the perception of the binaural beats may actually heighten.
Audio with binaural beats embedded into them can have an effect on synchronized brain waves, which are associated with hypongogic and meditative states. Since the ear is wired to both hemispheres of the brain, when a binaural beat is perceived there are actually separate waves present in each side. This means that binaural beats create synchronization between both of these portions of the brain, lending to a relaxed and meditative state.