Remember the recent post about binaural beats?
When two tones at slightly different frequencies are presented separately to your ears via headphones, the brain produces a phenomenon resulting in low-frequency pulsations in the loudness of a perceived sound. A beating tone will be perceived, as if the two tones mixed naturally.
According to some research, binaural beats [...]

Gnaural is a multi-platform programmable binaural-beat generator, implementing the principle of binaural beats as described in the October 1973 Scientific American article Auditory Beats in the Brain (Gerald Oster).
It can be used to synthesize sounds that affect the brain. Here’s a demo. It should be listened to using headphones:

 

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