These are sounds listened to using stereo headphones whose frequency differs from one ear to the other (identical sound content but different tones). Binaural signals were observed for the first time by the German scientist HW Dove in 1839. It was however Doctor Gérald Oster who was the first in 1973 to demonstrate the effect of this type of sound on cortical waves in the context of research on hearing acuity; it is also he who called them “binaural sounds”.
The difference in frequencies has two effects:
First of all this difference in frequencies is treated at the level of the upper olive nuclei of each hemisphere which then produce brain waves of the same frequency as the difference; these new waves propagate from these nuclei progressively throughout the cortex. Thus, for example to produce alpha waves, listen to sounds that differ from 8 to 13 Hz, which corresponds to the frequency of the alpha waves; this phenomenon was called by Atwater (1975) “frequency following response”.
These sounds also make it possible to synchronize the two cerebral hemispheres (Foster, 1990), synchronization which would induce a state of well-being, an improvement in mood, better attention and memory performance, processing of emotions and a decrease in anxiety. The use of the binaural beats meditation comes useful following this logic.
They are in the frequency range from 20 to 20,000Hz, the frequencies usable to induce states of relaxation are not in this range. On the other hand, the use of binaural sounds allows the processing of the difference in frequency by the brain, which then produces waves of differential frequency, usable with a view to action on the brain waves.
In this work, we have chosen to use a sound with a frequency difference of 8 to 10 Hz, at the center of the range of alpha waves. Alpha waves are in fact between fast beta waves stimulating attention and slow theta waves promoting learning. We wanted to test the effects of this frequency on various cognitive functions as well as on mood and emotion. We will thus study in turn the effects of binaural sounds of alpha frequency on attention, on working memory and on memorization through neuropsychological tests usually used in clinics as well as on computerized tasks taken from remediation software.
We will then try to highlight an effect of these alpha frequency sounds on the processing of emotions by means of an alexithymia scale and an emotional intelligence scale. Finally, we will evaluate the effect of ten weeks of training to listen to these 8-10 Hz frequency difference sounds on mood and anxiety, using the clinical scales usually used.