MPEG Digital Audio Coding Standards
Typical audio signal classes are telephone speech, wideband speech, and wideband audio, all of which differ in bandwidth, dynamic range and in listener expectation of offered quality. The quality of telephone-bandwidth speech is acceptable for telephony and for some videotelephony and videoconferencing services. Higher bandwidths (7 kHz for wideband speech) may be necessary to improve the intelligibility and naturalness of speech. Wideband (high ﬁdelity) audio representation including multichannel audio is expected in entertainment applications such as recorded music, motion picture sound tracks and digital audio broadcast (DAB), providing bandwidths of at least 15 kHz but more typically 18-20 kHz.