White noise machines produce random sound, and even mix of frequencies much like the sound produced by a waterfall or by wind blowing through the leaves of a tree. White noise can be very useful, thus white noise machines, or white noise generators, are available in a number of different forms, with many different feature sets.
White noise can be used for audio testing and sound masking, as well as for sleep aids and relaxation. White noise, because of its spread across all audible frequencies, can be very effective at masking or cancelling out ambient sounds, such as street noise or conversation. Thus, white noise machines are often employed for privacy in offices and waiting rooms. By reducing distracting noise, these machines frequently serve to increase productivity at workplaces.
White noise machines are also used for relaxation, to act as a sleep aid, or for power-napping. The soothing and distraction-reducing sound of white noise is often very effective for lulling people to sleep. Sometime white noise is combined with natural sounds such as rainfall or ocean waves. These sound conditioners, sound screens, or sleep machines can be portable and battery powered, and can feature sleep timers, volume controls, and a variety of additional relaxing sounds. Brands include Sleepmate, Marpac Marsona, ObusForme, Sound Oasis, Life Sounds, and Spalight.
White noise generators can also be used by tinnitus sufferers to mask the sound of ringing in their ears.
White noise machines can be electronic, operating either by producing random noise in real time or by playing back a recorded loop of white noise. There are also mechanical white noise machines that work by blowing air through small slots or baffles.