Wednesday, January 13, 2010

Ever heard about "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. Dove discovered that when two sounds, that are similar but slightly shifted in frequency, are presented separately to the left and right ear (Binaural) they will cause a pulsation or beat type effect in the brain.

For example, if a pure tone of 400 Hz is presented to the right ear and a pure tone of 410 Hz is presented simultaneously to the left ear, an amplitude modulated standing wave of 10 Hz, the difference between the two tones, is experienced as the two wave forms mesh in and out of phase within the superior olivary nuclei.

The human auditory apparatus can hear sounds with a pitch as low as about 20Hz (Hertz = cycles per second), give or take a few Hertz. However, the frequency of brainwaves—particularly those associated with states of relaxation and sleep—can go much lower, even below 1Hz. So a recording of a sound at, say, 4Hz would be inaudible and would have no effect. However, if you pitch two sounds exactly 4Hz apart (say, one at 100Hz and the other at 104Hz) and play one in each ear, the brain “manufactures” a 4Hz beat.

EEG and the brain's state

The binaural-beat appears to be associated with an electroencephalographic (EEG) frequency-following response in the brain.

EEG (Electroencephalography) technology is used to measure brain's electrical vibrations from the surface of the scalp. The resulting EEG pattern will contain frequency elements mainly below 30Hz. The frequencies are categorized into four states as follows:

The dominant frequency in the EEG pattern determines what shall be called the current state of the brain. If the amplitude of the alpha range frequencies is highest, then the brain is said to be in the alpha stage.

Proven theories

"The subjective effect of listening to binaural beats may be relaxing or stimulating, depending on the frequency of the binaural-beat stimulation" (Owens & Atwater, 1995). Binaural beats in the delta (1 to 4 Hz) and theta (4 to 8 Hz) ranges have been associated with reports of relaxed, meditative, and creative states (Hiew, 1995), and used as an aid to falling asleep.

Binaural beats in the alpha frequencies (8 to 12 Hz) have increased alpha brain waves (Foster, 1990) and binaural beats in the beta frequencies (typically 16 to 24 Hz) have been associated with reports of increased concentration or alertness (Monroe, 1985) and improved memory (Kennerly, 1994).

Brainwaves have been found to mimic the effect of certain drugs:

And some other effects:

For more information:

Worth to try: (free stuff)

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