The homedics deep sleep I white noise machine provides advanced white noise therapy that offers 4 distinct tones to help you fall asleep and stay asleep. "soothe" setting is like a gentle rain, with the lightest pitched tone that gently eases your mind. "mask" setting is designed to mask external distractions including noisy neighbors and highway traffic. "relax" is modulated to disrupt interfering room noise, such as snoring. "calm" is the deepest of all the tone settings, which is perfect for tinnitus sufferers and small children. Tone control allows you to manually adjust the tone of the white noise to best fit your needs. A built-in timer lets you set session length for 30, 60 or 90 minutes. The deep sleep is for your bedside or portable use, giving you a good night"s sleep wherever you are. An adaptor (included) or 4 "AA" batteries (not included).