Gamma waves are neural oscillation patterns that are created in the brains of humans. They are linked to higher performances of mental and cognitive functioning, and they induce higher states of conciousness and awareness. Many gamma waves are recorded as binaural sounds that can be listened to. Many gamma wave sounds can be sold as music CDs or they can be listened to online for free. Their frequency is between 25 to 100 Hz, though 40 Hz is prototypical.
Listening to gamma waves will help train your brain to create the same type of oscillation patterns, making you more likely to have higher intelligence and induce better cognitive performance.