Marpac Sleepmate 980A Electro Mechanical Sound Conditioner. I wondered if it could really do the job. 5 3/4 inch base diameter:

The tone and volume of the sound are controlled by simply rotating the cap. Jan 08, 2012 11:17:33 | usually ships in 24 hours. When i turned the unit on, i noticed the sound it generates comes from a small fan.