...It can be done for several reasons: people with insomnia can take great benefit from it, but it can also be used to improve your attention span, and even simulate the effects of some recreational drugs.
The effect is not permanent, and fades away in less than a minute after the stimuli is removed.
Isochronic tones are a commonly used aural stimuli for Brainwave Entrainment, consisting of short pulses of a sine wave, varying in frequency.
Unlike binaural beats, isochronic tones can be played on speakers.
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