Surround sound is a technique for enriching the fidelity and depth of sound reproduction by using multiple audio channels from speakers that surround the listener (surround channels). Its first application was in movie theaters. Prior to surround sound, theater sound systems commonly had three screen channels of sound that played from three loudspeakers (left, center, and right) located in front of the audience. Surround sound adds one or more channels from loudspeakers to the side or behind the listener that are able to create the sensation of sound coming from any horizontal direction (at ground level) around the listener. The technique enhances the perception of sound spatialization by exploiting sound localization: a listener's ability to identify the location or origin of a detected sound in direction and distance. This is achieved by using multiple discrete audio channels routed to an array of loudspeakers. Surround sound typically has a listener location (sweet spot) where the audio effects work best and presents a fixed or forward perspective of the sound field to the listener at this location. Surround sound formats vary in reproduction and recording methods, along with the number and positioning of additional channels. The most common surround sound specification, the ITU's 5.1 standard, calls for 6 speakers: center (C), in front of the listener; left (L) and right (R), at angles of 60°; left surround (LS) and right surround (RS) at angles of 100–120°; and a subwoofer, whose position is not critical. Surround sound can benefit audio contents with large dynamic range, such as movies and games.
Fields of application Though cinema and soundtracks represent the major uses of surround techniques, its scope of application is broader than that, as surround sound permits the creation of an audio environment for all sorts of purposes. Multichannel audio techniques may be used to reproduce contents as varied as music, speech, natural or synthetic sounds for cinema, television, broadcasting, or computers. In terms of music content for example, a live performance may use multichannel techniques in the context of an open-air concert, of a musical theatre performance or for broadcasting; for a film, specific techniques are adapted to movie theater or to home (e.g. home cinema systems). The narrative space is also a content that can be enhanced through multichannel techniques. This applies mainly to cinema narratives, for example the speech of the characters of a film, but may also be applied to plays performed in a theatre, to a conference, or to integrate voice-based comments in an archeological site or monument. For example, an exhibition may be enhanced with topical ambient sound of water, birds, train or machine noise. Topical natural sounds may also be used in educational applications. Other fields of application include video game consoles, personal computers and other platforms. In such applications, the content would typically be synthetic noise produced by the computer device in interaction with its user. Significant work has also been done using surround sound for enhanced situation awareness in military and public safety applications.
Types of media and technologies Commercial surround sound media include videocassettes, DVDs, and SDTV broadcasts encoded as analog matrixed Dolby Surround, compressed Dolby Digital, and DTS, and lossless audio such as DTS-HD Master Audio and Dolby TrueHD on HDTV, Blu-ray Disc, and HD DVD, which are identical to the studio master. 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 and DTS. Sony Dynamic Digital Sound (SDDS) is an 8-channel cinema configuration that features 5 independent audio channels across the front with two independent surround channels, and a Low-frequency effects channel. Traditional 7.1 surround speaker configuration introduces two additional rear speakers to the conventional 5.1 arrangement, for a total of four surround channels and three front channels, to create a more 360° sound field. 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 and DVD-Audio formats. Some AV receivers, stereophonic systems, and computer sound cards contain integral digital signal processors or digital audio processors to simulate surround sound from a stereophonic source (see fake stereo). In 1967, the rock group Pink Floyd performed the first-ever surround sound concert at "Games for May", a lavish affair at London’s Queen Elizabeth Hall where the band debuted its custom-made quadraphonic speaker system. The control device they had made, the Azimuth Co-ordinator, is now displayed at London's Victoria and Albert Museum, as part of their Theatre Collections gallery. Netflix can support DRM-protected surround sound, but if the TV set or audio device does not support Dolby-based DRM, it will fall back to stereo.
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