The brain produces very small rhythmic electrical pulses which are called brainwave patterns. These patterns can be observed using electroencephalograph (EEG) scanning equipment. Brainwaves are measured in cycles per second (Hz) and are produced by different areas of the brain throughout the day and night.
40 – 70 Hz are associated with higher mental functioning including, perception, intelligent problem solving, self awareness, compassion as well as emotional responses such as happiness and fear.
13 – 40 Hz are known to be predominant during periods of concentration, activity, anxiety and arousal.
7 – 13 Hz are linked to creativity and the state of conscious relaxation and calmness.
4 – 7 Hz are associated with right-brain and subconscious insightful thinking, deep relaxation and mental imagery as well as meditation and REM sleep.
0.5 – 4 Hz occur during periods of deep dreamless sleep and are linked to healing, recovery and pain relief.
The brain can be stimulated by sounds which have a rhythmic pulse matching the frequency range of specific brainwaves. This process is known as entrainment and has been shown to be very effective in producing the desired therapeutic states associated with each type of brainwave. It is a technique with roots in ancient practices such as shamanic drumming or the use of gongs, bells and chanting in meditation and it is now the subject of much scientific research.
When two sounds with slightly different frequencies are heard simultaneously the sounds combine to form a rhythmic pulse knowns as a binaural tone or binaural beat. The frequency of the pulse depends on the difference in frequencies of the two original sounds – if the first sound is 400Hz and the second is 380Hz the resulting binaural tone will have a frequency of 20Hz.
Binaural tones can be used very effectively to entrain brainwave patterns by targeting frequencies usually within the Alpha, Theta and Delta ranges. They can be used as pure tones, or embedded within ambient music, natural sounds such as ocean waves, or within different kinds of noise. The entrainment process works best using headphones but can also be experienced using stereo speakers – make sure your ears are the same distance from each speaker!
Binaural beats can be used by most people with no risk of any harmful side effects, however there are specific issues where caution is required when using this technology.