Binaural beats are sounds perceived in the mind as the result of hearing different tones simultaneously. The effect was discovered by Heinrich Wilhelm Dove in 1839 and most recently gained popularity because of its ability to alter brainwaves and affect levels of relaxation, creativity and more. Binaural beats occur when two different tone levels are played and the brain hears the tone that is the difference between the two beats. For example, if 200Hz is played in one ear and 210Hz in the other ear, the binaural tone would be 10Hz. The aural stimulus results in brainwave entrainment.
Brainwave entrainment occurs when binaural beats are introduced to the brain and the brain perceives a sound frequency that is the difference between the two beats heard. The beat frequency is subsonic, where the frequency ranges that induce mental states that are related to relaxation and sleep occur. Each ear hears a steady tone, and the brain perceives the sound that is the difference of the tones. Brainwave entrainment is often used to treat emotional and mental disorders, as well as increase the levels of relaxation for use with hypnosis and meditation.
The brain is normally not able to hear tones that are lower than 20Hz, however these low tones are thought to produce desired mental states such as a state of deep relaxation or meditation. Because of this, binaural beats are increasingly popular in fields such as hypnosis and meditation. Binaural beats are used to achieve highly relaxed and meditative states through augmented brainwaves. For binaural beats to have the desired effect, the frequencies of the tones must be lower than 1,000Hz. The person hearing the beats must also be using stereo headphones so that two separate tones can be sounded in each ear at the same time. The brain produces low-frequency pulsations as a result of hearing the binaural beats and creates a perceived sound. If the difference in the two frequencies of the beats is too large, the binaural beat will not be heard.
Binaural beats are thought to help with many problems, such as reducing anxiety and dealing with pain management. This is due to the fact that binaural beats have the ability to induce various states of consciousness depending on the perceived frequency that is heard. Binaural beat stimulation can induce mental states that deal with relaxation, focus and attention.
Human hearing is limited to the range of 20Hz to 20,000Hz frequency levels. However, when binaural beats are used, the brain is capable of hearing frequencies much lower. These low frequencies are where the alteration of brainwaves creating altered mental states occurs. Brainwaves entrain, or move towards a frequency, when the perceived beat is in the alpha, beta, theta, delta or gamma range of brainwave frequencies. These frequency ranges are all associated with different mental states and moods. Using binaural beats can help achieve the desired perceived frequency, and therefore the desired mental state or mood.
A perceived frequency range of around 40Hz is in the gamma range and is normally associated with consciousness, fear, problem solving and generally higher mental activity. The gamma range is at the high end of perceived frequencies. As you get lower on the scale, more meditative moods result. The range from 13-39Hz is called beta and is normally associated with active thoughts, arousal, concentration and paranoia. Alpha waves are the range of 7-13Hz and are associated with a state of relaxation while still awake, REM sleep and dreaming. The 4-7Hz Theta waves range is associated with deep, NREM sleep. Under 4Hz is known as the Delta range when deep, dreamless sleep occurs.