Homedics Deep Sleep White Noise Machine is only white noise machine that is truly adjustable. Tone and volume controls allow you to create the perfect white noise for your environment and four distinct white noise tones to help you fall asleep and stay asleep. Perfect for bedside or portable use. 4 distinct tones include Soothe: Like a gentle rain, this tone has the lightest pitch?gently easing your mind; Mask: Designed to mask external distractions including noisy neighbors and highway traffic; Relax: Modulated to disrupt interfering room noise, such as snoring; Calm: The deepest of all tones. Perfect for tinnitus sufferers & small children. Bedside or portable use adapter or 4 "AA" batteries to get a good night?s sleep wherever you are (batteries not included); Built-in timer can be set for 30, 60 or 90 minutes; Simple, elegant speaker design provides powerful, room-filling sound.