(1) See also HD Radio.
(2) (High Definition audio) Higher-quality digital music formats. See high-resolution audio.
(4) (High Definition Audio) A specification for audio and modem circuits on a PC motherboard. Introduced in 2004 by Intel and superseding AC'97, HD Audio provides eight channels (7.1) of 32-bit, 192 kHz audio for Dolby Digital and DTS surround sound. It allows the same port to be used for speaker or microphone (automatic jack retasking), and it supports multiple listening zones. HD Audio Link Like AC'97, HD Audio comprises a controller connected to analog/digital codecs by a 5-wire TDM interface called "HD Audio Link." The two subsystems separate the digital controller, which is built into the PC chipset, from the analog circuits, which can be in a chip on the motherboard or interchangeable riser card, the latter often used for international modem certification (homologation). See AC'97 and riser card.