Surround sound, using multichannel audio, encompasses a range of techniques for enriching (expanding and deepening) the sound reproduction quality, of an audio source, with additional audio channels reproduced via additional, discrete speakers. The three-dimensional (3D) sphere of human hearing can be virtually achieved with audio channels above and below the listener. To that end, the multichannel surround sound application encircles the audience (left-surround, right-surround, back-surround), as opposed to "screen channels" (center, [front] left, and [front] right), i.e. ca. 360° horizontal plane, 2D).
Surround sound technology is used in cinema and home theater systems, video game consoles, personal computers and other platforms. Commercial surround sound media include videocassettes, Video DVDs, and HDTV broadcasts encoded as Dolby Pro Logic, Dolby Digital, or DTS. Other commercial formats include the competing DVD-Audio (DVD-A) and Super Audio CD (SACD) formats, and MP3 Surround. Cinema 5.1 surround formats include Dolby Digital, DTS, and Sony Dynamic Digital Sound (SDDS).
Most surround sound recordings are created by film production companies or video game producers; however some consumer camcorders have such capability either built-in or available separately. Surround sound technologies can also be used in music to enable new methods of artistic expression. After the failure of quadraphonic audio in the 1970s, multichannel music has slowly been reintroduced since 1999 with the help of SACD & DVD-Audio formats. Some AV receivers, stereophonic systems, and computer soundcards contain integral digital signal processors and/or digital audio processors to simulate surround sound from a stereophonic source.
