What is an MP3?
An MP3 is a digital audio file compressed with a standard defined by the Motion Pictures Experts Group (MPEG). MPEG was formed to develop techniques for dealing with digital video; since most video also contains audio, MP3 was developed as an audio extension of that work. Officially known as “MPEG-1, Layer 3”, MP3 is a lossy compression algorithm that uses psychoacoustic modeling to reduce the size of audio files by up to 90%. Psychoacoustics takes advantage of deficiencies in the human hearing system to throw away digital bits corresponding to sounds that cannot be heard. The human ear cannot hear soft sounds in the presence of loud sounds having a similar frequency; for example, a voice conversation becomes inaudible when a jet flies low overhead. This effect is known as auditory masking, and done correctly the discarded sounds will not be missed. MP3 is a lossy algorithm in the sense that the original bits cannot be recreated from the compressed bits. In terms of hearing, however, M
Many people use ‘mp3’ as a term synonymous to ‘music file’ or simple ‘song’. This is completely inaccurate – mp3 is simply one way of encoding a song. Other ways include the m4a (also called aac) and wma formats. These three formats all have something in common: they are all lossy. This means that they all compress the original song so that some data is lost in the process. This is where bitrate comes into the picture. The bitrate is usually expressed in terms of ‘kilobits per second’ – or kbps. A kilobit is a unit of space (similar to a megabyte) and a second is, well, a second. Therefore, the kbps value signifies how many kilobits of space each second of a song takes up. For example, a song encoded at 128kbps would take up 128 kilobits per second, whilst the same song encoded at 256kbps would take up 256 kilobits per second, and therefore be twice as big. A higher bitrate represents better quality but more space – there is a trade-off between quality and space.
MP3 is a way of storing music on your computer that makes the size of a song much smaller with virtually no loss in quality from the original CD. If you copy a three-minute song from CD onto your hard drive, it will take up about 30MB. In MP3 format, it only occupies 3MB! For more information about MP3s, you can go to ZDNet or mpeg.org.
