http://gethighnow.com/binaural-beats/
Binaural Beats 
Choose a Binaural Beat to suit your mood from the below. Note that in
order for Binaural Beats to work, they must be played though
headphones.
WARNING: DO NOT listen to Binaural Beats while driving, operating equipment, or any other task that requires concentration. DO NOT listen to Binaural Beats if you have experienced seizures in the past or have epilepsy. Those with heart  disorders or taking mood-altering pharmaceutical drugs should consult a  doctor before trying. We’re serious. Use common sense, people. Sure, Get High Now (without drugs). . .but don’t die! 
How It Works

When two tones of specific frequencies are played through headphones,
the brain can become confused and produce its own, imagined tone—a
three-dimensional audio hallucination heard only within the head of the
listener. The frequencies that produce this phenomenon are known as
Binaural Beats.

What is happening is that the brain is not used to hearing
frequencies in each ear so close together and with such intensity—these
sounds do not occur in nature and so a mechanism in our brains has not
evolved to understand them. Instead, the superior olivary nucleus, the
area of the brain which controls aspects of three-dimensional sound
perception, bridges the difference between the varying frequencies in
Binaural Beats with a common “third tone” in an attempt to normalize
this audio into something we can understand. What’s weirder is that
each person hears the “third tone” differently: People with Parkinson’s
disease can’t hear it at all; women will hear different tones as they
move through their menstrual cycle.

Binaural Beats were discovered in 1839 by Prussian physicist Heinrich
Wilhelm Dove (1803 – 1879) but they didn’t gain much public interest
until the early 1970s. Then, scientist Gerald Oster postulated that the
brain wasn’t solely affected by Binaural Beats. He tested this theory
with fMRIs and found he was right. The neurological system as well as
other parts of the body responded to the frequencies.
Since Oster’s discovery, Binaural Beats have been used as cure-alls
for everything from impotence to bulimia. Spurious, right? Sure, but the
difference between Binaural Beats, and, say, magic healing crystals, is
that Binaural Beats have been clinically shown to physically affect the
listener’s brain and body, even triggering the pituitary gland to flood
the body with good-feeling hormones like dopamine. In other words,
Binaural Beats are proven to get us mentally, physically,
physiologically, biologically, scientifically, inextricably high.

Remember that people hear Binaural Beats differently, and some may
have trouble hearing the “third tone” at all. How will you know if you
can hear them? Say you can, get some headphones, and try them out. Every
single member of HighLab heard them, and regaled Binaural Beats as one
of the most fantastic audio highs in this fantastic app. What are you
waiting for?