Surround sound

Multichannel audio techniques may be used to reproduce contents as varied as music, speech, natural or synthetic sounds for cinema, television, broadcasting, or computers.

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.

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.

[14] 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.

In 1978, a concept devised by Max Bell for Dolby Laboratories called "split surround" was tested with the movie Superman.

A French engineer, Dominique Bertrand used a mixing board specially designed in cooperation with Solid State Logic, based on 5000 series and including six channels.

The first and simplest method is using a surround sound recording technique—capturing two distinct stereo images, one for the front and one for the back or by using a dedicated setup, e.g., an augmented Decca tree[20]—or mixing-in surround sound for playback on an audio system using speakers encircling the listener to play audio from different directions.

A third approach, based on Huygens' principle, attempts reconstructing the recorded sound field wavefronts within the listening space; an "audio hologram" form.

Commercial WFS systems, currently marketed by companies sonic emotion and Iosono, require many loudspeakers and significant computing power.

There are many free and commercial software programs available for Ambisonics, which dominates most of the consumer market, especially musicians using electronic and computer music.

This way of creating surround with software routines is normally referred to as upmixing,[23] which was particularly successful on the Sansui QSD-series decoders that had a mode where it mapped the L ↔ R stereo onto an ∩ arc.

[25] The function of the center channel is to anchor the signal so that any central panned images do not shift when a listener is moving or is sitting away from the sweet spot.

[27] The center channel also prevents any timbral modifications from occurring, which is typical for 2-channel stereo, due to phase differences at the two ears of a listener.

[24][25] The localization of a virtual source, based on level differences between two loudspeakers to the side of a listener, shows great inconsistency across the standardized 5.1 setup, also being largely affected by movement away from the reference position.

Alternatively, backward facing cardioid microphones can be placed closer to the front array for a similar reverberation pickup.

Two additional omnidirectional outriggers can be added to enlarge the perceived size of the orchestra or to better integrate the front and surround channels.

The surround microphones are usually placed at the critical distance (where the direct and reverberant field is equal), with the full array usually situated several meters above and behind the conductor.

The L, R, LS and RS microphones pick up early reflections from both the sides and the back of an acoustic venue, therefore giving significant room impressions.

[25] The microphones nulls (zero pickup point) are set to face the main sound source with positive polarities outward facing, therefore very effectively minimizing the direct sound pickup as well as echoes from the back of the hall[26] The back two microphones are mixed to the surround channels, with the front two channels being mixed in combination with the front array into L and R. Another ambient technique is the IRT (Institut für Rundfunktechnik) cross.

It was originally developed to carry extremely low sub-bass cinematic sound effects (e.g., the loud rumble of thunder or explosions) on their own channel.

This allowed theaters to control the volume of these effects to suit the particular cinema's acoustic environment and sound reproduction system.

Independent control of the sub-bass effects also reduced the problem of intermodulation distortion in analog movie sound reproduction.

[29] Some record labels such as Telarc and Chesky have argued that LFE channels are not needed in a modern digital multichannel entertainment system.

PanAmbio combines a stereo dipole and crosstalk cancellation in front and a second set behind the listener (total of four speakers) for 360° 2D surround reproduction.

5.1 channel recordings, including movie DVDs, are compatible by mixing C-channel content to the front speaker pair.

7.1 surround sound is a popular format in theaters & Home cinema including Blu-rays with Dolby and DTS being major players.

[45] Dolby Atmos (and other Microsoft Spatial Sound engines; see AudioObjectType in SpatialAudioClient.h) additionally support a virtual "8.1.4.4" configuration, to be rendered by a HRTF.

[47] 10.2 is the surround sound format developed by THX creator Tomlinson Holman of TMH Labs and University of Southern California (schools of Cinema/Television and Engineering).

Developed along with Chris Kyriakakis of the USC Viterbi School of Engineering, 10.2 refers to the format's promotional slogan: "Twice as good as 5.1".

[48] 22.2 is the surround sound component of Ultra High Definition Television, developed by NHK Science & Technical Research Laboratories.