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Biaural Beats

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Binaural beats influence functions of the brain besides those related to hearing. This phenomenon is called frequency following. What happens is that if one receives a stimulus with a frequency in the range of brain waves, the predominant brain wave frequency moves towards the frequency of the stimulus (a process called entrainment). In addition, binaural beats have been credibly documented to relate to both spatial perception & stereo auditory recognition, and, according to the frequency following response, activation of various sites in the brain.

The stimulus does not have to be aural; it can also be visual or a combination of aural and visual. (One such example would be Dreamachine.) However, using alpha frequencies with such stimuli can trigger photosensitive epilepsy.

Perceived human hearing is limited to the range of frequencies from 20 Hz to 20,000 Hz, though Infrasound - sound below 20Hz - still have scientifically observable effects on humans, however, it is not readily audible, especially at low volume levels. While the frequencies of human brain waves are below about 40 Hz. To account for this lack of perception, binaural beat frequencies are used. Beat frequencies of 40 Hz have been produced in the brain with binaural sound and measured experimentally.

When the perceived beat frequency corresponds to the delta, theta, alpha, beta, or gamma range of brainwave frequencies, the brainwaves entrain to or move towards the beat frequency. For example, if a 315 Hz sine wave is played into the right ear and a 325 Hz one into the lefft ear, the brain is entrained towards the beat frequency (10 Hz, in the alpha range. Since alpha range is associated with relaxation, this has a relaxing effect or if in the beta range, more alertness. An experiment with binaural sound stimulation using beat frequencies in the Beta range on some participants and Delta/Theta range in other participants, found better vigilance performance and mood in those on the awake alert state of Beta range stimulation.

Binaural beat stimulation has been used fairly extensively to induce a variety of states of consciousness, and there has been some work done in regards to the effects of these stimuli on relaxation, focus, attention, and states of consciousness. Studies have shown that with repeated training to distinguish close frequency sounds that a plastic reorganization of the brain occurs for the trained frequencies and is capable of asymmetric hemispheric balancing.

Brain Wave Patterns

Frequency range  Name                      Usually associated with:

> 40 Hz                      Gamma waves  Higher mental activity, including perception, problem solving, fear, and consciousness

13–40 Hz                Beta waves          Active, busy or anxious thinking and active concentration, arousal, cognition

7–13 Hz                       Alpha waves          Relaxation (while awake), pre-sleep and pre-wake drowsiness

4–7 Hz                         Theta waves          Dreams, deep meditation, REM sleep

2-4 Hz                          Delta Waves           Deep Meditation, Coma

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Binaural Beats".