Human beings display five different types of electrical patterns or "brain waves" across the cortex, which can be observed with an EEG (or an "electroencephalograph"). Each brain wave has a purpose and are part of a normal mental functioning.
Normally, we must be able to transition among the different patterns. If we cannot, we become sick. Exercising a control over the transition process can help us managing stress, focusing on tasks, and getting a good night's sleep.
The five types of brain waves often display together. However, depending on the mental state of the person, one becomes dominant over the others. Therefore, a sound leads us predominantly.
Gamma waves (40 Hz to 100 Hz) are involved in higher processing tasks as well as cognitive functioning. If they are excessive, they cause anxiety, high arousal, stress. If they are lacking, they cause ADHD, depression, learning disabilities. If they are balanced, they cause senses to operate together, cognition, information processing, learning, perception, REM sleep. When we increase them through concentration, they also lead to meditation.
Beta waves (12 Hz to 40 Hz) are commonly observed while we are awake. They are involved in conscious thought, logical thinking, learning, and tend to have a stimulating affect. If they are excessive, they cause adrenaline, anxiety, high arousal, inability to relax, stress. If they are lacking, they cause ADHD, daydreaming, depression, poor cognition. If they are balanced, they cause conscious focus, memory, problem solving. We can increase them with coffee, energy drinks, and various stimulants.
Alpha waves (8 Hz to 12 Hz) bridge the gap between our conscious thinking and subconscious mind. They help us calm down and promote deep relaxation. If they are excessive, they cause daydreaming, inability to focus, being too relaxed. If they are lacking, they cause anxiety, high stress, insomnia, OCD. If they are balanced, they cause relaxation. We can increase them with alcohol, marijuana, relaxants, and some antidepressants.
Theta waves (4 Hz to 8 Hz) are involved in daydreaming and sleep. They allow us to experience deep and raw emotions. If they are excessive, they cause ADHD, depression, hyperactivity, impulsivity, inattentiveness. If they are lacking, they cause anxiety, poor emotional awareness, stress. If they are balanced, they cause creativity, emotional connection, intuition, relaxation. We can increase them with alcohol, marijuana, relaxants, and some depressants.
Delta waves (0 Hz to 4 Hz) are most often produced in infants and young children. As we age, we produce them less, even during deep sleep. They are involved in the deepest levels of relaxation and restorative, healing sleep. They also regulate unconscious bodily functions (heart beat and digestion). If they are excessive, they cause brain injuries, learning problems, inability to think, severe ADHD. If they are lacking, they cause inability to rejuvenate one's body and revitalize one's brain, poor sleep. If they are balanced, they cause a good immune system, natural healing, a restorative deep sleep. We can increase them with depressants and deep sleep.
As we can see, an imbalance in any type of wave generally causes anxiety, which then manifests at different levels.
Estensive researches have been performed in the brain wave range, which led to many discoveries. For example, delta waves at 2.5 Hz promote the production of endogenous opiates (pain killers, anxiety reduction) and relieves migraine pain. Theta waves at 4.9 Hz induce relaxation and deeper sleep. In general, brain waves have been classified according to the following table.
Attention, senses operating together, focus, compassion, consciousness, meditation, mental processing, perception, R.E.M. sleep, subjective awareness, unity of consciousness
Addiction, anger, antidepressant effect, anxiety, alertness, attention, awakeness, energy, excitement, focus, insomnia, IQ increase, memory, muscle tension, negative thinking, paranoia, positive thinking, Rapid thinking or "quick wit", stress
Balanced, mood, calm, creativity, daydreaming, decreased focus, flowing state of mind and thoughts, immune system boost, peak performance, positive thinking, problem solving, relaxation, serotonin, slower visual acuity, super learning, visualization
ADHD, creativity, depression, emotions, healing, hyperfocus, immune system boost, impulsivity, intuition, learning, long-term or childhood memories, meditation, paranormal activity, PTSD, sleep, spiritual states, stress reduction, connection with the subconscious mind
Advanced healing, anti-aging, deep sleep, empathy, GHB production, Growth hormone (HGH) production, immune system boost, intuition, learning disabilities, unconscious mind processes
It was found that we can introduce in the brain a certain frequency and influence it. This works is a similar way to resonance. The brain "resonates" at the introduced frequency, which becomes dominant against the other brain waves. In this manner, we can induce sleep, free a person from depression, help someone focusing on something he is learning, etc.
One way we can introduce a frequency in the brain is by feeding it to the ears - i.e. simply playing a sound. The ear will produce the equivalent electrical signal, which it will send to the brain.
It may be noted that brain frequencies are very low and generally fall outside the range of loudspeakers. Therefore, a different way to produce them needed to be devised.
This led to the use of the interference caused by two sounds played simultaneously. When two frequencies are played, they also produce another two frequencies - i.e. their sum and their difference. The frequency resulting from the difference is called binaural beat.
For example, if a 530 Hz pure sine wave is played together with a 520 Hz pure sine wave, the listener will also hear 1050 Hz and 10 Hz. The latter is the binaural beat. The following graph shows two waves (one is dark blue and the other is azure) and their resulting difference below (red).
It was found that, the same way it happens in air, it also happens directly inside the brain, if we apply one frequency to one ear and the other frequency to the other ear. The beat frequency is generated directly by the brain. This way, we need no exotic loudspeaker, but simply any headphone.
Binaural beats allow us to re-program our mind, remove imbalances, restore a healthy bodily condition, promote our well-being.
Musicians can use any DAW (Digital Audio Workstation) to produce binaural files ready for any need. They will send a tone to the left speaker and another tone to the right one. The sounds need to be simple sine waves. Composers can introduce binaural basses to induce certain moods or mental states in his public. Composers Giacinto Scelsi and Phill Niblock developed a style grounded on microtonal oscillations of unisons, extensively exploring the textural effects of interference beats.
In an orchestra, many binaural beats happen at once. A section of violins is easily distinguished from a single violin because different player can never play the same exact sound. It is likely that everyone of them will play at a slightly different offset. That is why classical music has a natural predisposition to re-tune our mind, as it is rich in binaural beats.
When the orchestra is off-tune and offsets become bigger than required, binaural beats are no longer generated. Disturbing frequencies are added, which contribute to tarnish the overall sound. This is in turn perceived by the listeners as off-keys.