For much of the history of the wristwatch, mechanical movements were perfectly content to tick along at 2.5 or 3 Hz, measuring time at a leisurely 18,000 or 21,600 vibrations per hour, respectively.

Cowritten by Charlie Huntington and Tchiki Davis. Binaural beats are what happens when two equally loud sounds, at just slightly different frequencies (or tones), are presented at the same time, one ...