Brainwave entrainment and synchronization is a result of two different sound frequencies presented to each ear, say 408hz and 400hz. The brain detects the phase difference between these signals, 8hz. Under normal circumstances the brain would see this phase difference as directional information, but when heard through stereo headphones the brain process this information differently. A perceptual integration of the two signals takes place producing the sensation of a third beat frequency. As the two different input frequencies mesh in and out of phase an amplitude modulating standing wave called a binaural beat is heard. This beat is perceived as a fluctuating rhythm at the frequency of the difference between the two input frequencies, in the above case 8hz. This binaural beat is created within the brain. Binaural beats can easily be heard at frequencies below 30hz and can be relaxing or stimulating depending on the frequency. Brainwave entrainment is taking you to the naturally occurring brain wave patterns that you enter every day during each 24 hour period.

Electroencephalography (EEG) is the study of changing electrical potential of the brain. According to their frequency, brain waves are divided into four main groups.

Beta:- 14hz plus.
Alpha:- 8- 14hz
Theta:- 4- 8hz
Delta:- 0.3-4hz

Although we operate in all these frequencies throughout the day, and various parts of the brain can and do operate at different frequencies all the time, we can assume a generalisation of the dominant frequencies. Although one frequency may be dominant, at a given time, depending on the activity of the individual, there will be still trace levels of the remaining three at all times.

Beta, 14hz +

Most adults are operation in this frequency when we are fully awake and alert. This is generally associated with left-brain thinking. The logical, critical, analytical thinking mind, the fully conscious mind. Associated with increased alertness.

Alpha, 8-14hz
Generally associated with right brain thinking or the subconscious mind. This is a relaxed state of daydreaming, also associated with accelerated learning. Children spend more time in the Alpha and Theta stage than adults, which probably explains their accelerated learning capabilities.

Theta, 4-8hz
Deeply relaxed, dreaming, again associated with the subconscious mind, but the deeper subconscious that bring forth insights and bursts of creative ideas.

Delta, 0.3-4hz
Generally associated with being unconscious, no thinking, a state of regeneration and rejuvenation. Also a state of super conscious in meditation, body asleep, mind awake.

When the brain is entrained to lower frequencies and awareness is maintained, a unique state of consciousness emerges. This is typical of people meditating, but what is also evident in deep meditation is the two hemispheres of the brain synchronize in frequency.

Studies have shown that vibrations of rhythmic sounds have a profound effect on brain frequency. In shaman traditions the periodic beating of a drum at 4.5 beats per second was the key to transporting the shaman to a higher consciousness. The Buddhists chants are designed for the same reason. It is already well known that if you place two violins side by side and pluck the string of one, the string on the other will vibrate at the same frequency, this is call resonance.

Audio with embedded binaural beats has the ability to induce and improve states of consciousness such as meditation or relaxed alertness. Each ear is connected to a sound processing centre called the olivary nucleus in each hemisphere of the brain, so there are two waves of equal amplitude and frequency present, one in each hemisphere. When both hemispheres are entrained to the same frequency we see hemispheric synchronization, and brain function is enhanced through the increase of cross communication between the left and right hemispheres of the brain.

Passively listening to binaural beats may not spontaneously create an altered state of consciousness. As with hypnosis, it is the willingness and the ability of the listener to relax and focus attention that may contribute to its effectiveness in inducing state changes. The effect of binaural beat stimulation is said to be enhanced through the addition of white noise, pink noise or brown noise. Music, guided imagery, verbal suggestions and breathing exercises can also heighten the effectiveness of binaural beat stimulation. Recent studies on hypnotic susceptibility, suggests that highly hypnotizable subjects produce more anterior theta activity than low and medium-susceptible individuals. Using binaural beat induced theta activity produced an increase in hypnotic susceptibility. Studies have also indicated that the use of self-hypnosis recordings or binaural beat stimulation can produce depths of relaxation that were similar, and the combination of both is more powerful than the use of either used alone.

When a certain brainwave state is experienced and practiced over time, through habitual response the brain will develop the ability to produce the brainwave state at will, without the need for brainwave stimulation.