Alpha sound is a soft 10 cycles per second sound, that through an imitation process guides the brain to lower and stable brain frequencies, that make it easier to relax and practice mind control.
Their relaxing and therapeutic effect is so important that in some cases only playing the Alpha sound in a room full of noisy children, after a few minutes all of them entered in a lower and relaxed brain frequency (for the joy of their teacher)
Theta sound induces deeper meditation levels,
and that´s why it´s preferred by those that want to get into deeper levels of the mind, or practice astral travel or yoga.
This soft sounds will help you reach levels of the brain related with the most absolute peaceful and relaxing state.
You can read more about the Alpha Sound HERE
You can read more about the Theta Sound HERE