Dr. Cheryl Fraser: How To Have Better Sex & Intimacy (Archived Interview)
Back in 1839, a German physicist named Heinrich Wilhelm Dove noticed something odd about the way the human brain responds to sound. When slightly different tones reach each ear, the perceptual system reacts in a particular way, and Dove was the first person to document that effect.
Dove was no fringe figure. He held a fellowship with the Royal Society and ran the Prussian Meteorological Institute, so his observation sat inside a serious scientific career rather than outside of it.
For more than a century the finding stayed largely academic. Then, roughly between the 1950s and the 1970s, various researchers and inventors turned Dove's original observation into a working audio technique. Several people have since claimed credit for that practical technology, but the underlying effect traces back to Dove's early work.
The reason any of this matters for relaxation and mindfulness is simple enough: the same auditory stimulus can be used to nudge the brain toward calmer states. If you want to read the actual research rather than take anyone's word for it, searching PubMed for terms like mindfulness and the psychological effects of brainwave entrainment will turn up published studies.
One caveat worth stating plainly. None of these claims have been reviewed or approved by the FDA, and nothing here is meant to diagnose or treat any condition.