"The binaural-beat
appears to be associated
with an electroencephalographic [EEG]
frequency-following response in the brain.
Many studies have demonstrated the presence of a frequency-following response to auditory stimuli, recorded at the vertex of the human brain [top of the head].
This EEG activity was termed "frequency-following response" because its period corresponds to the fundamental
frequency of the stimulus."
[Smith, Marsh, & Brown, 1975]
"The FFR provides evidence that the sensations of binaural beats have neurological efficacy." [Atwater]

pure sine waves: in harmonic resonance with the body's core