Binaural beats
A binaural beat is an auditory illusion. It is perceived when two different pure-tone sine waves are presented to a listener, one tone to each ear.[1]
For example, if a 530 Hz pure tone is presented to a subject's right ear, while a 520 Hz pure tone is presented to the subject's left ear, the listener will perceive the illusion of a third tone. The third sound is called a binaural beat, and in this example would have a perceived pitch correlating to a frequency of 10 Hz, that being the difference between the 530 Hz and 520 Hz pure tones presented to each ear.[2][3]
They may help people with pain when they are in hospital.[4] Some people use binaural beats to help them sleep, meditate or have out of body experiences.[5] There are computer programs and smartphone programs that make binaural beats.
Many of the claims are not verified at present.[6]
History
Heinrich Wilhelm Dove (1803–1879) discovered binaural beats in 1839 and published his findings in the scientific journal Repertorium der Physik.[7] While research about them continued after that, the subject remained something of a scientific curiosity until 134 years later, with the publishing of Gerald Oster's article "Auditory beats in the brain" (Scientific American, 1973). Oster's article identified and assembled the scattered pieces of relevant research since Dove, offering fresh insight (and new laboratory findings) to research on binaural beats.[3]
Oster saw binaural beats as a powerful tool for cognitive and neurological research. Unsolved questions include how animals locate sounds in their environment: the remarkable ability of animals to pick out and focus on specific sounds in a sea of noise (known as the cocktail party effect).
Binaural Beats Media
Beating of two frequencies
The sum (blue) of two sine waves (red, green) is shown as one of the waves increases in frequency. The two waves are initially identical, then the frequency of the green wave is gradually increased by 25%. Constructive and destructive interference can be seen.
A 110Hz A sine wave (magenta) and a 104Hz G# one (cyan). Their sum (blue) and the corresponding envelope (red). See:
How binaural beats would sound after being processed within the brain
To experience the binaural beats perception, it is best to listen to this file with headphones on moderate to weak volume – the sound should be easily heard, but not loud. The sound appears to pulsate only when heard through both earphones. Time duration of 10 seconds
Binaural Beats Base tone 200 Hz, beat frequency from 7 Hz to 12.9 Hz. Time duration of 9 minutes.
References
- ↑ Both tones have frequencies lower than 1500 Hz, with less than a 40 Hz difference between them.
- ↑ "Binaural Beats". Psychology, Neuroleadership, & Neurofeedback. Retrieved 2018-08-26.[dead link]
- ↑ 3.0 3.1 Oster G. 1973. Auditory beats in the brain. Sci. Am. 229 (4): 94–102.
- ↑ Hemispheric-synchronisation during anaesthesia: a double-blind randomised trial using audiotapes for intra-operative nociception control, Jan 2000, Kliempt, Ruta, Ogston, Landeck & Martay
- ↑ Accessing anomalous states of consciousness with a binaural beat technology Archived 2012-05-07 at the Wayback Machine Journal of Scientific Exploration. 1, (3) pp. 263-274, 1997
- ↑ Wahbeh H. et al 2007. Binaural beat technology in humans: a pilot study to assess neuropsychologic, physiologic, and electroencephalographic effects. Journal of alternative and complementary medicine 13 (2): 199–206. [1]
- ↑ Heinrich Wilhelm Dove 1839. Repertorium der Physik. III, 494.