Very loud!
I have always used a noise maker for sleep - ranging from electronic noisemakers to box fans.  I was excited about the Marpac because it's mechanical, which seems to have the best sound quality.  Alas, this unit was way too loud for my bedroom, even at its lowest setting.  I think it would be great for a very large room or perhaps a collection of rooms.  It also vibrates a bit, which made my wooded bedside table resonate unpleasantly.  I reckon I'll stick with my box fan.
Rating: 2 stars