Reduction of bandwidth or data rate for audio. Many digital schemes are in use, all of which make use of the way the ear hears (e.g. that a loud sound will tend to mask a quieter one) to reduce the information sent. Generally this is of benefit in areas where bandwidth or storage is limited, such as in delivery systems to the home, hand-held players, etc. Generally the terms ‘coding’ or ‘codec’ refer to a compression scheme, such as MP3.