I know that there are such sounds.
I found some time to the music that helps you fall asleep.
[youtube]http://www.youtube.com/watch?v=xQ6xgDI7Whc[/youtube]
[youtube]http://www.youtube.com/watch?v=m_rSzzopAXo[/youtube]
However, I am wondering if there are any sounds that I could listen to on headphones when I read an academic book to make it is easier to memorize