A form of audio compression based on the MPEG format for video. Users specify a bit rate — the number of kilobits to be used for each second — and the MP3 encoder will discard differences in the sound signal sufficient to achieve this. Lower bit rates thus give smaller files but lower sound quality on playback. Bit rates of 32 kbps or higher will compress speech significantly without a discernible loss of quality; however, at least 128 kbps is required for music. MP3 files are a highly popular format for downloads of music from the Internet. MP3 players, capable of storing large numbers of music tracks in flash memory, and playing the tracks through earphones, are also popular. See also iPod.