Binaural beats

Binaural beats or binaural tones are auditory processing artifacts, or apparent sounds, the perception of which arises in the brain independent of physical stimuli. This effect was discovered in 1839 by Heinrich Wilhelm Dove. The brain produces a phenomenon resulting in low-frequency pulsations in the loudness of a perceived sound when two tones at slightly different frequencies are presented separately, one to each of a subject's ears, using stereo headphones. A beating tone will be perceived, as if the two tones mixed naturally, out of the brain. The frequency of the tones must be below about 1,000 to 1,500 hertz for the beating to be heard. The difference between the two frequencies must be small (below about 30 Hz) for the effect to occur; otherwise, the two tones will be heard separately and no beat will be perceived. Binaural beats are of interest to neurophysiologists investigating the sense of hearing. Second, binaural beats reportedly influence the brain in more subtle ways through the entrainment of brainwaves and can be used to produce relaxation and other health benefits such as pain relief.