I have been suffering from sleep issues, not being able to fall asleep and/or staying asleep, for years. I read an article about the Dohm unit and decided to try it. WOW! The first time I used it I realized I was able to shut my brain off and fall directly to sleep. If I woke up in the middle of the night, I was able to fall right back to sleep. No more staying awake thinking about all sorts of crazy things! I track my sleep using my FitBit (for what its worth) and noticed a HUGE change in the quality of sleep-more time in REM and deep sleep and less time restless/awake. I just purchased another unit to use at our summer house. My one issue is that I do hear a high pitched whine using the slower speed. But I just use the higher speed and have no issues.