abbreviation of MPEG-1, audio layer 3 Standard technology and format for the compression of audio signals into very small computer files. For example, sound data from a compact disc (CD) can be compressed to one-twelfth the original size without sacrificing sound quality. Because of small file size and ease of production from CD sources, the MP3 format is very popular for transmitting music files over the Internet. Although recording companies have sued many Web sites for facilitating the exchange of such copyrighted material, many now provide sample songs in MP3 format to promote CD sales, and some musicians bypass recording companies and issue their songs over the Internet in MP3 format only. See also data compression