Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Sound masking is the addition of natural or artificial sound (commonly, though inaccurately, referred to as "white noise" or "pink noise") into an environment to cover-up unwanted sound by using auditory masking. This is in contrast to the technique of active noise control. Sound masking reduces or eliminates awareness of pre-existing sounds in a given area and can make a work environment more comfortable, while creating speech privacy so workers can better concentrate and be more productive. Sound masking can also be used in the outdoors to restore a more natural ambient environment.