how loud ?

since ive been back ive tried turning on my mp3 player to turn on one of those mp3's that help induce sleep, says things like you are dreaming this is a dream and has nice ambient music

but it seems like i just cant hear it after a while and fall asleep, if i turn it on too loud i will get totally woken up after 4-5 hours of sleep.

so what do you people do ??

I know the "directions" on some mp3 files state that you should have it only loud enough so that you can make out what is being said (if there are words spoken) but not so loud that it will keep you awake.

The key is does it state that it's ok to fall asleep or does it state that all benefit will be lost if you do? If you don't know the answer to that question.. ask the person/company that created the mp3 file.
.

thanks