I've actually tried the
Immrama Institutes FOCUS CD, with pretty good results, and pretty weird results when used incorrectly. I listen to it while working to help me focus. It’s a 2 CD set, with three tracks. The sound waves are masked using the simple sound of falling rain. I find it very relaxing and less distracting than music.
I tried experimenting with different scenarios:
So far I’ve acheived heightened concentration and relaxation while working or studying.
When used in combination with my meditation it seems to heighten my focus. (This was an experiment. This CD is not actually supposed to be used for meditation; the Insight CD was created for that.)
If I listen to it before sleeping, I stay in half sleep/half wake lucid state most of the night. (Interesting, but not fun after a couple of days.) I do remember my dreams, though.
Overall I would say the best benefits can be reaped from a steady diet of listening for the recommended 20 minutes a day. The affects seem to last at least a couple of hours. Definitely worth the money.