Here is a gift you can give yourself or any friend who you know is suffering from sleep deprivation or even insomnia. The Harmonic Sleep CD from Sound Health Products does offer the usual soothing sounds to make you sleep but features subliminal “harmonics” that are said to encourage slow, relaxing sleep waves in the brain even though they are too faint to hear. Alternatively, the Delta Sleep System CD contains tones that supposedly match the frequency of delta sleep waves, in theory cuing the brain to make sleep waves of its own.
Both CDs are sold at various site
