Binaural beats cause the brainstem to generate interaural time differences, to which the brain entrains, generating particular brainwaves.

“Binaural beats as the name suggests are beats delivered to the two ears. One pattern of kind of percussive beat to one ear and a different pattern or at least a pattern that's out of phase that's not synchronized delivered to the other ear. So on one ear you hear d and in the other ear you've got dun dun dun. And what happens is because of the way that the auditory system converges in the brain stem and generates what are called intraoral time differences. I'll explain what that means in a moment. intraoral time differences. The difference between the two patterns of beats that are heard by the each of the two different ears leads to a third pattern that the brain entrains to and kind of maps onto and generates particular types of brain waves.”