Guys....do you not realise that everything is sound or frequency? I think the frequency of sleep is 4hz....and so if I put a frequency of 100hz in your left ear, and a frequency of 104hz in your right ear...you'll fall asleep! There's a frequency of laughter..of all sorts of things! It's VERY VERY good for your mind to use Solfeggio Frequencies! I'm amazed people don't know about this stuff!