This is the free ad-supported version of Binaural. Headphones are required.
Generate custom binaural tones for your headphones. You can either use one of the presets to quickly get an appropriate beat, or you can customize from a wide selection of frequencies and beats. The presets take the closest appropriate tone from the Oster curve.
For more information on binaural beats, see the wikipedia page here: http://en.wikipedia.org/wiki/Binaural_beats