ream with variable rates between 32 kbps and 384 kbps. MP2 is a part of digital audio broadcasting (DAB) and digital video broadcasting (DVB) standards and is commonly used for professional recording by radio stations. The MP2 standard is also used in the video CD (VCD) system. Of the three MPEG-1 audio standards MP3 is the most popularly known and used. It has applications in audio coding for recording, storing and sharing music and is used in most portable music players. It is also commonly used for streaming music. Similar to voice com- pression standards such as AMR, MP3 also analyses audio signals by dividing the input signal into sub-bands of many different frequencies. The encoder then filters out information that is perceptually insignificant: any sound that cannot be perceived by the human auditory system is discarded. For example if a particular frequency of a signal has a large amplitude, it can mask its neighbouring frequencies which have lower amplitudes. This phenomenon is known as auditory masking. Encoding such masked information is not necessary as our ears cannot hear it. Using this principle, an MP3 source coder can reduce the number of bits used by only providing information that is perceptually significant to the human ear [17]. The sub-band information is further Huffman coded to minimise the number of bits used. The MP3 standard specifies sampling rates of 16, 22.05, 24, 32, 44.1 and 48 kHz, and produces bit rates in a 32-320 kbps range. These bit rates represent significant reductions compared with an audio CD coding rate of 1.411 Mbps. It should be noted that audio encoders such as MP3 work in a different way to voice encoders such as AMR. Voice coders analyse the generation of voice signals by the human vocal system in order to efficiently encode it. In contrast audio coders analyse how our auditory system perceives audio in order to efficiently encode it. MPEG standards of which MP3 is part are globally ratified through the International Organisation for Standardisation (ISO). In genera