Binaural beats correspond to a sound illusion effect that occurs when two tones at close frequencies are emitted to the left and right ears (eg via headphones or speakers), giving the sensation of a beat.
It was in 1839 that a Prussian physicist, Heinrich Wilhelm Dove, realized that this phenomenon occurs when the following conditions are met :
- Sine waveform;
- Left and right frequencies lower than 1000 Hertz (Hz);
- Difference of 40 Hertz or less between the two frequencies.
Left ear : 261,915 Hz
Right ear : 254,085 Hz
Binaural beats cause particular effects on the brain via so-called brain waves, electrical activity acting on brain cells, according to the frequency ranges.
The main types of brain waves are :
• Beta waves (14 Hz – 40Hz) : Occur when one is aware and alert;
• Alpha waves (7.5 Hz – 14Hz) : Corresponds to a state of deep relaxation / light meditation / light sleep;
• Theta waves (4 Hz – 7.5Hz) : Appear during meditative, slumbery states / light sleep / hypnosis;
• Delta waves (0.5 Hz – 4Hz) : Associated to deep states of unconsciousness / sleeping;
• infra-low (< 0.5 Hz) : Low frequency rhythmic activity whose role is not yet well known. Seems to play an important role in brain timing and network function;
• Gamma waves (above 40 Hz) : This range is the most recently discovered, it goes with a high level of brain activity and concentration peaks.
Binaural beats can be used in particular for relaxation purposes, or even in a therapeutic setting (preferably under the guidance of health professionals).