You might receive the dual speed version
I have used the Marpac Dohm white noise machines for several years, and find them very helpful at masking noises when I sleep. When our old dual speed Dohm developed a rattle, I decided to try the single speed version, so I ordered this one, model M1SSUSTN, where SS indicates single speed, and TN indicates the tan color. However, when it arrived, it was the model M1DSUSTN, which is a dual speed model. I decided to keep it rather than send it back, although Amazon does charge more for the single speed model than the dual speed model (which isn't logical).
Rating: 4 stars