Playing Sound During Sleep to Improve Memory
Science has never given much credence to claims that you can learn Chinese or French by having the instruction CDs play while you sleep. If any learning happens that way, most scientists say, the language lesson is probably waking the sleeper up, not causing nouns and verbs to seep into a sound-asleep mind.
Scientists at Northwestern University reported that playing specific sounds while people slept helped them remember more of what they had learned before they fell sleep, to the point where memories of individual facts were enhanced.