There are three sources of white noise that are commonly used to help mask out annoying sounds: mechanically generated, electronically generated and recordings usually on CD format.

The mechanical devices produce a sound very close to that of a fan. The Sleepmate by Marpac is this type of device and has been around for a long time. This is the most popular type of white noise machine; probably because it produces a sound that we are all familiar with and don’t find unpleasant. One drawback of the mechanical units is that they are limited in volume. Since they produce the sound mechanically, it isn’t possible to simply turn up the volume.

White noise is commonly generated with a digital or electronic sound synthesizing device. Sound designers, with some processing and filtering, can create a multitude of effects such as wind, rain, waterfall or surf. The main consideration when choosing a digital device is if the device loops a recorded clip of sound or synthesizes its own sound. By looping we refer to a few seconds of sound that is digitally recorded and played over and over. They try to match up the end with the beginning but if you listen carefully you can detect where the segment begins - this is irritating to some people. The better digital sound devices actually synthesize the sound instead of playing a recording, therefore no looping.