Brain waves

[galaxy_storm]

I generated a wave file with 200hz sine wave in one channel and 204hz in the other one, converted to mp3 and put on my mp3 player. The 4hz difference is in theta wave range which is according to http://lunarsight.com/freq.htm is "Extrasensory perception; Astral Projection". At first few tries it worked quite well got me into the hypnagogic state, but a few nights ago, something weird happened. When that night I said enough for today and turned off my mp3 player, I could hear a nasty dull humming sound from inside of my head, which then became intermittent and faded away after few minutes. Yesteday night after some 20 minutes listening to the brain waves, I started to hear a tone that should not be there. The tone was about 1khz, not stable in pitch and volume, and moved slowly from my left ear to right, then back, sometimes in both ears. When I turned off the player it again faded in few minutes.
What are these sounds I'm hearing? To my understanding brain waves are not harmful for the brain?? Should I stop using the brain waves or should I ignore the sounds and tones? The tone I heard last night was pretty loud.  And no, I'm not playing the brain waves too loud.

[keyangen]

I have listened to mp3 brainwave for a few years, though I gave it up like a year ago. They haven't helped me much to be honest, but they definitely haven't done any harm, although I've had loads of strange experiences of all kinds while listening to them. I don't think you have anything to worry about, if you find that they help you achieve trance state or have interesting experiences, go ahead and use them.