Surround sound
Overview
 
Surround sound encompasses a range of techniques such as for enriching the sound reproduction
Sound recording and reproduction
Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording...

 quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or 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. There are other non surround based formats.
Encyclopedia
Surround sound encompasses a range of techniques such as for enriching the sound reproduction
Sound recording and reproduction
Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording...

 quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or 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. There are other non surround based formats. The three-dimensional (3D) sphere of human hearing can be virtually achieved with audio channels that surround the listener. To that end, the multichannel surround sound application encircles the audience with surround channels
Surround channels
Surround channels are audio channels in surround sound multichannel audio. They primarily serve to deliver ambience and diffuse sounds in a film or music soundtrack...

 (left-surround, right-surround, back-surround), as opposed to "screen channels" (center
Center channel
Center channel refers to an audio channel common to many surround sound formats. It is the channel that is mostly, or fully, dedicated to the reproduction of the dialogue of an audiovisual program...

, [front] left, and [front] right), i.e. ca. 360° horizontal plane (2D).

Fields of application

Though cinema and soundtrack
Soundtrack
A soundtrack can be recorded music accompanying and synchronized to the images of a motion picture, book, television program or video game; a commercially released soundtrack album of music as featured in the soundtrack of a film or TV show; or the physical area of a film that contains the...

s represent the major uses of surround techniques, its scope of application is broader than that as surround sound permits to create 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
Multichannel television sound
Multichannel television sound, better known as MTS , is the method of encoding three additional channels of audio into an NTSC-format audio carrier.- History :...

, 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
Concert
A concert is a live performance before an audience. The performance may be by a single musician, sometimes then called a recital, or by a musical ensemble, such as an orchestra, a choir, or a musical band...

, of a musical theatre
Musical theatre
Musical theatre is a form of theatre combining songs, spoken dialogue, acting, and dance. The emotional content of the piece – humor, pathos, love, anger – as well as the story itself, is communicated through the words, music, movement and technical aspects of the entertainment as an...

 or for broadcasting
Broadcasting
Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...

; for a film
Film score
A film score is original music written specifically to accompany a film, forming part of the film's soundtrack, which also usually includes dialogue and sound effects...

 specific techniques are adapted to movie theater
Movie theater
A movie theater, cinema, movie house, picture theater, film theater is a venue, usually a building, for viewing motion pictures ....

, or to home (e.g. home cinema
Home cinema
Home cinema, also commonly called home theater, are home entertainment set-ups that seek to reproduce a movie theater experience and mood with the help of video and audio equipment in a private home....

 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
Diegesis
Diegesis is a style of representation in fiction and is:# the world in which the situations and events narrated occur; and# telling, recounting, as opposed to showing, enacting.In diegesis the narrator tells the story...

 of the characters
Character (arts)
A character is the representation of a person in a narrative work of art . Derived from the ancient Greek word kharaktêr , the earliest use in English, in this sense, dates from the Restoration, although it became widely used after its appearance in Tom Jones in 1749. From this, the sense of...

 of a film
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...

, but may also be applied to plays
Play (theatre)
A play is a form of literature written by a playwright, usually consisting of scripted dialogue between characters, intended for theatrical performance rather than just reading. There are rare dramatists, notably George Bernard Shaw, who have had little preference whether their plays were performed...

 for theatre
Theatre
Theatre is a collaborative form of fine art that uses live performers to present the experience of a real or imagined event before a live audience in a specific place. The performers may communicate this experience to the audience through combinations of gesture, speech, song, music or dance...

, to a conference, or to integrate voice-based comments in an archeological site or monument. For example, an exhibition
Exhibition
An exhibition, in the most general sense, is an organized presentation and display of a selection of items. In practice, exhibitions usually occur within museums, galleries and exhibition halls, and World's Fairs...

 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
Situation awareness
Situation awareness, situational awareness, or SA, is the perception of environmental elements with respect to time and/or space, the comprehension of their meaning, and the projection of their status after some variable has changed, such as time...

 in military and public safety applications.

Types of media and technologies

Commercial surround sound media include videocassettes, DVDs
DVD-Video
DVD-Video is a consumer video format used to store digital video on DVD discs, and is currently the dominant consumer video format in Asia, North America, Europe, and Australia. Discs using the DVD-Video specification require a DVD drive and a MPEG-2 decoder...

, and HDTV broadcasts encoded as compressed Dolby Digital
Dolby Digital
Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally called Dolby Stereo Digital until 1994. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints...

 and DTS, and lossless audio such as DTS HD Master Audio and Dolby TrueHD
Dolby TrueHD
Dolby TrueHD is an advanced lossless multi-channel audio codec developed by Dolby Laboratories which is intended primarily for high-definition home-entertainment equipment such as Blu-ray Disc and HD DVD. It is the successor to the AC-3 Dolby Digital surround sound codec which was used as the...

 on Blu-ray Disc
Blu-ray Disc
Blu-ray Disc is an optical disc storage medium designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Blu-ray Discs contain 25 GB per layer, with dual layer discs being the norm for feature-length video discs...

 and HD DVD
HD DVD
HD DVD is a discontinued high-density optical disc format for storing data and high-definition video.Supported principally by Toshiba, HD DVD was envisioned to be the successor to the standard DVD format...

, which are identical to the studio master. Other commercial formats include the competing DVD-Audio
DVD-Audio
DVD-Audio is a digital format for delivering high-fidelity audio content on a DVD. DVD-Audio is not intended to be a video delivery format and is not the same as video DVDs containing concert films or music videos....

 (DVD-A) and Super Audio CD
Super Audio CD
Super Audio CD is a high-resolution, read-only optical disc for audio storage. Sony and Philips Electronics jointly developed the technology, and publicized it in 1999. It is designated as the Scarlet Book standard. Sony and Philips previously collaborated to define the Compact Disc standard...

 (SACD) formats, and MP3 Surround
MP3 Surround
MP3 Surround is an extension of MP3 for multi-channel audio support including 5.1 surround sound. It was developed by Fraunhofer IIS in collaboration with Thomson and Agere Systems, and released in December 2004....

. Cinema 5.1 surround formats include Dolby Digital
Dolby Digital
Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally called Dolby Stereo Digital until 1994. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints...

 and DTS. Sony Dynamic Digital Sound (SDDS) is an 8 channel cinema configuration which 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 camcorder
Camcorder
A camcorder is an electronic device that combines a video camera and a video recorder into one unit. Equipment manufacturers do not seem to have strict guidelines for the term usage...

s 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
Quadraphonic
Quadraphonic sound – the most widely used early term for what is now called 4.0 surround sound – uses four channels in which speakers are positioned at the four corners of the listening space, reproducing signals that are independent of one another...

 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 soundcards contain integral digital signal processors and/or digital audio processors to simulate surround sound from a stereophonic source.

In 1967, the rock group Pink Floyd
Pink Floyd
Pink Floyd were an English rock band that achieved worldwide success with their progressive and psychedelic rock music. Their work is marked by the use of philosophical lyrics, sonic experimentation, innovative album art, and elaborate live shows. Pink Floyd are one of the most commercially...

 performed the first-ever surround sound concert at “Games for May”, a lavish affair at London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

’s Queen Elizabeth Hall
Queen Elizabeth Hall
The Queen Elizabeth Hall is a music venue on the South Bank in London, United Kingdom that hosts daily classical, jazz, and avant-garde music and dance performances. The QEH forms part of Southbank Centre arts complex and stands alongside the Royal Festival Hall, which was built for the Festival...

 where the band debuted its custom-made quadraphonic speaker system. The control device they had made, the Azimuth Co-ordinator
Azimuth co-ordinator
The Azimuth Co-ordinator was the first panning control for a quadraphonic sound system, at that time a new concept. Pink Floyd became the first band to use it in their early shows.The Azimuth Co-ordinator uses four rotary rheostats housed in a large box...

, is now displayed at London's Victoria and Albert Museum
Victoria and Albert Museum
The Victoria and Albert Museum , set in the Brompton district of The Royal Borough of Kensington and Chelsea, London, England, is the world's largest museum of decorative arts and design, housing a permanent collection of over 4.5 million objects...

, as part of their Theatre Collections gallery.

History

The first documented use of surround sound was in 1940, for the Disney studio's animated film Fantasia
Fantasia (film)
Fantasia is a 1940 American animated film produced by Walt Disney and released by Walt Disney Productions. The third feature in the Walt Disney Animated Classics series, the film consists of eight animated segments set to pieces of classical music conducted by Leopold Stokowski, seven of which are...

. Walt Disney
Walt Disney
Walter Elias "Walt" Disney was an American film producer, director, screenwriter, voice actor, animator, entrepreneur, entertainer, international icon, and philanthropist, well-known for his influence in the field of entertainment during the 20th century. Along with his brother Roy O...

 was inspired by Rimsky Korsakov's operatic piece, Flight of the Bumblebee
Flight of the Bumblebee
"Flight of the Bumblebee" is an orchestral interlude written by Nikolai Rimsky-Korsakov for his opera The Tale of Tsar Saltan, composed in 1899–1900. The piece closes Act III, Tableau 1, during which the magic Swan-Bird changes Prince Gvidon Saltanovich into an insect so that he can fly away to...

to have a bumblebee
Bumblebee
A bumble bee is any member of the bee genus Bombus, in the family Apidae. There are over 250 known species, existing primarily in the Northern Hemisphere although they are common in New Zealand and in the Australian state of Tasmania.Bumble bees are social insects that are characterised by black...

 featured in his musical Fantasia
Fantasia (film)
Fantasia is a 1940 American animated film produced by Walt Disney and released by Walt Disney Productions. The third feature in the Walt Disney Animated Classics series, the film consists of eight animated segments set to pieces of classical music conducted by Leopold Stokowski, seven of which are...

and also sound as if it was flying in all parts of the theatre - the unsuccessful experimentation led to the music being excluded from the film and the eventual invention of "surround sound".

The initial multichannel audio application was called 'Fantasound
Fantasound
Fantasound was a stereophonic sound reproduction system developed by the engineers of Walt Disney studios for its 1940 animated film Fantasia, the first commercial film to be released in stereo. Fantasound led to the development of what is known today as surround sound.-Origins:Walt Disney's...

', comprising three audio channels and speakers. The sound was diffused throughout the cinema, initially by an engineer using some 54 loudspeakers. The surround sound was achieved using the sum and the difference of the phase of the sound. In the 1950s, the German composer Karlheinz Stockhausen
Karlheinz Stockhausen
Karlheinz Stockhausen was a German composer, widely acknowledged by critics as one of the most important but also controversial composers of the 20th and early 21st centuries. Another critic calls him "one of the great visionaries of 20th-century music"...

 experimented with and produced ground-breaking electronic compositions such as Gesang der Jünglinge
Gesang der Jünglinge
Gesang der Jünglinge is a noted electronic music work by Karlheinz Stockhausen. It was realized in 1955–56 at the Westdeutscher Rundfunk studio in Cologne and is Work Number 8 in the composer's catalog of works...

and Kontakte
Kontakte (Stockhausen)
Kontakte is a celebrated electronic music work by Karlheinz Stockhausen, realized in 1958–60 at the Westdeutscher Rundfunk electronic-music studio in Cologne with the assistance of Gottfried Michael Koenig .-Work history:The title of the work “refers both to contacts between instrumental and...

, the latter using fully discrete and rotating quadraphonic sounds generated with industrial electronic equipment in Herbert Eimert's studio at the Westdeutscher Rundfunk
Westdeutscher Rundfunk
Westdeutscher Rundfunk is a German public-broadcasting institution based in the Federal State of North Rhine-Westphalia with its main office in Cologne. WDR is a constituent member of the consortium of German public-broadcasting institutions, ARD...

(WDR). Edgar Varese's Poeme Electronique
Poème électronique
Poème électronique is a piece of electronic music by composer Edgard Varèse, written for the Philips Pavilion at the 1958 Brussels World’s Fair. The Philips corporation commissioned Le Corbusier to design the pavilion, which was intended as a showcase of their engineering progress...

, created for the Iannis Xenakis
Iannis Xenakis
Iannis Xenakis was a Romanian-born Greek ethnic, naturalized French composer, music theorist, and architect-engineer. He is commonly recognized as one of the most important post-war avant-garde composers...

 designed Philips Pavilion
Philips Pavilion
The Philips Pavilion was a World's Fair pavilion designed for Expo '58 in Brussels by the office of Le Corbusier. Commissioned by Philips, an electronics company based in the Netherlands, the pavilion was designed to house a multimedia spectacle that celebrated postwar technological progress...

 at the 1958 Brussels World's Fair, also utilised spatial audio with 425 loudspeakers used to move sound throughout the pavilion. There are also many other composers that created ground-breaking surround sound works in the same time period.
5.1 surround sound originated in 1987 at the famous French Cabaret Moulin Rouge
Moulin Rouge
Moulin Rouge is a cabaret built in 1889 by Joseph Oller, who also owned the Paris Olympia. Close to Montmartre in the Paris district of Pigalle on Boulevard de Clichy in the 18th arrondissement, it is marked by the red windmill on its roof. The closest métro station is Blanche.The Moulin Rouge is...

. A French engineer, Dominique Bertrand used a mixing board specially designed in cooperation with Solid State Logic
Solid State Logic
Solid State Logic is a manufacturer of high-end mixing consoles and recording studio hardware headquartered in Begbroke, Oxfordshire, UK.- Company information :...

, based on 5000 series and including 6 channels. Respectively: A left, B right, C centre, D left rear, E right rear, F bass. The same engineer had already achieved a 3.1 system in 1974, for the International Summit of Francophone States in Dakar
Dakar
Dakar is the capital city and largest city of Senegal. It is located on the Cap-Vert Peninsula on the Atlantic coast and is the westernmost city on the African mainland...

 Senegal.

Creating surround sound

Surround sound is created in several ways. The first and simplest method is using a surround sound recording microphone technique, and/or mixing-in surround sound for playback on an audio system using speakers encircling the listener to play audio from different directions. A second approach is processing the audio with psychoacoustic sound localization
Sound localization
Sound localization refers to a listener's ability to identify the location or origin of a detected sound in direction and distance. It may also refer to the methods in acoustical engineering to simulate the placement of an auditory cue in a virtual 3D space .The sound localization mechanisms of the...

 methods to simulate a two-dimensional (2-D) sound field with headphones. A third approach, based on Huygens' principle, attempts reconstructing the recorded sound field wave fronts within the listening space; an "audio hologram" form. One form, wave field synthesis
Wave field synthesis
Wave field synthesis is a spatial audio rendering technique, characterized by creation of virtual acoustic environments. It produces "artificial" wave fronts synthesized by a large number of individually driven speakers. Such wave fronts seem to originate from a virtual starting point, the virtual...

 (WFS), produces a sound field with an even error field over the entire area. Commercial WFS systems, currently marketed by companies sonic emotion and Iosono, require many loudspeakers and significant computing power.

The Ambisonics
Ambisonics
Ambisonics is a series of recording and replay techniques using multichannel mixing technology that can be used live or in the studio. By encoding and decoding sound information on a number of channels, a 2-dimensional or 3-dimensional sound field can be presented...

 form, also based on Huygens' principle, gives an exact sound reconstruction at the central point; less accurate away from center point. There are many free and commercial software available for Ambisonics, which dominates most of the consumer market, especially musicians using electronic and computer music. Moreover, Ambisonics products are the standard in surround sound hardware sold by Meridian Audio, Ltd.
Meridian Audio, Ltd.
Boothroyd Stuart Meridian is a British manufacturer of high-performance, high-fidelity audio and video components and systems. Founded in 1977 by Bob Stuart and Allen Boothroyd, its products have proved popular among music and movie enthusiasts, and more recently in the lifestyle technology and...

 In its simplest form, Ambisonics consumes few resources, however this is not true for recent developments, such as Near Field Compensated Higher Order Ambisonics. Some years ago it was shown that, in the limit, WFS and Ambisonics converge.

Finally, surround sound also can be achieved by mastering level, from stereophonic sources as with Penteo
Penteo
Penteo is a digital audio, stereo-to-5.1 surround conversion process based on a mashup of Avery Lee's open source Center Cut algorithm from VirtualDub combined with Hans Van Zutphen's freeware Tape Restore Live azimuth corrector...

, which uses Digital Signal Processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...

 analysis of a stereo recording to parse out individual sounds to component panorama positions, then positions them, accordingly, into a five-channel field. There are however more ways to create surround out of stereo, for instance with routines based on the QS and SQ Quad routines, where instruments were in the studio divided over 4 speakers. This way of creating surround with software routines is normally referred to as "upmixing".

Mapping channels to speakers

In most cases, surround sound systems rely on the mapping of each source channel to its own loudspeaker. Matrix systems recover the number and content of the source channels and apply them to their respective loudspeakers. With discrete surround sound, the transmission medium allows for (at least) the same number of channels of source and destination; however, one-to-one, channel-to-speaker, mapping is not the only way of transmitting surround sound signals.

The transmitted signal might encode the information (defining the original sound field) to a greater or lesser extent; the surround sound information is rendered for replay by a decoder generating the number and configuration of loudspeaker feeds for the number of speakers available for replay – one renders a sound field as produced by a set of speakers, analogously to rendering in computer graphics. This "replay device independent" encoding is analogous to encoding and decoding an Adobe PostScript file, where the file describes the page, and is rendered per the output device's resolution capacity. The Ambisonics and WFS systems use audio rendering; the Meridian Lossless Packing contains elements of this capability

Bass management

Surround replay systems may make use of bass management
Bass management
The fundamental principle of bass management in surround sound replay systems is that bass content in the incoming signal, irrespective of channel, should be directed only to loudspeakers capable of handling it, whether the latter are the main system loudspeakers or one or more special...

, the fundamental principle of which is that bass content in the incoming signal, irrespective of channel, should be directed only to loudspeakers capable of handling it, whether the latter are the main system loudspeakers or one or more special low-frequency speakers called subwoofers.

There is a notation difference before and after the bass management system. Before the bass management system there is a Low Frequency Effects (LFE) channel. After the bass management system there is a subwoofer signal. A common misunderstanding is the belief that the LFE channel is the "subwoofer channel". The bass management system may direct bass to one or more subwoofers (if present) from any channel, not just from the LFE channel. Also, if there is no subwoofer speaker present then the bass management system can direct the LFE channel to one or more of the main speakers.

Low Frequency Effects (LFE) channel

Because the Low Frequency Effects channel requires only a fraction of the bandwidth of the other audio channels, it is referred to as the ".1" channel; for example "5.1" or "7.1".

The LFE is a source of some confusion in surround sound. The LFE channel was originally developed to carry extremely low "sub-bass" cinematic sound effects (with commercial subwoofers sometimes going down to 30 Hz
HZ
Hz is the International Standard symbol for Hertz, the unit of frequencyHZ may also stand for:* Habitable zone, the distance from a star where a planet can maintain Earth-like life* Hamilton Zoo, in New Zealand...

, 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
Intermodulation
Intermodulation or intermodulation distortion is the amplitude modulation of signals containing two or more different frequencies in a system with nonlinearities...

 in analog movie sound reproduction.

In the original movie theater implementation, the LFE was a separate channel fed to one or more subwoofers. Home replay systems, however, may not have a separate subwoofer, so modern home surround decoders and systems often include a bass management system that allows bass on any channel (main or LFE) to be fed only to the loudspeakers that can handle low-frequency signals. The salient point here is that the LFE channel is not the "subwoofer channel"; there may be no subwoofer and, if there is, it may be handling a good deal more than effects.

Some record labels such as Telarc and Chesky have argued that LFE channels are not needed in a modern digital multichannel entertainment system. They argue that all available channels have a full frequency range and, as such, there is no need for an LFE in surround music production, because all the frequencies are available in all the main channels. These labels sometimes use the LFE channel to carry a height channel, underlining its redundancy for its original purpose. The label BIS generally uses a 5.0 channel mix.

Surround sound specifications

The descriptions of surround sound specifications below distinguish between the number of discrete channels encoded in the original signal and the number of channels reproduced for playback. The number of channels reproduced for playback can be changed by using matrix decoding
Matrix decoder
Matrix decoder is an audio technology where a finite number of discrete audio channels are decoded into a larger number of channels on play back...

. A distinction is also made between the number of channels reproduced for playback and the number of speakers used to reproduce (each channel may refer to a group of speakers). The graphics to the right of each specification description represent the number of channels, not the number of speakers.

Notation

This notation, e.g. "5.1", reflects the number of full range channels; including a ".1" to reflect the limited range of the LFE channel.

E.g. 2 basic stereo speakers with no LFE channel = 2.0


5 full-range channels + 1 LFE channel = 5.1

It can also be expressed as the number of full-range channels in front of the listener, separated by a slash from the number of full-range channels beside or behind the listener, separated by a decimal point from the number of limited-range LFE channels.

E.g. 3 front channels + 2 side channels + an LFE channel = 3/2.1

This notation can then be expanded to include the notation of Matrix Decoder
Matrix decoder
Matrix decoder is an audio technology where a finite number of discrete audio channels are decoded into a larger number of channels on play back...

s. Dolby Digital EX, for example, has a sixth full-range channel incorporated into the two rear channels with a matrix
Matrix decoder
Matrix decoder is an audio technology where a finite number of discrete audio channels are decoded into a larger number of channels on play back...

. This would be expressed:

3 front channels + 2 rear channels + 3 channels reproduced in the rear in total + 1 LFE channel = 3/2:3.1

Note: The term stereo
Stereophonic sound
The term Stereophonic, commonly called stereo, sound refers to any method of sound reproduction in which an attempt is made to create an illusion of directionality and audible perspective...

, although popularised in reference to two channel audio, can also be properly used to refer to surround sound, as it strictly means "solid" (actually meaning 3 dimensional sound) sound. However this is no longer a common usage and "stereo sound" is almost exclusively used to describe two channel, left and right, sound.

Channel identification

In accordance with ANSI/CEA-863-A
Zero-based order within multi-channel
mp3
MP3 Surround
MP3 Surround is an extension of MP3 for multi-channel audio support including 5.1 surround sound. It was developed by Fraunhofer IIS in collaboration with Thomson and Agere Systems, and released in December 2004....

/wav
WAV
Waveform Audio File Format , is a Microsoft and IBM audio file format standard for storing an audio bitstream on PCs...

/flac
FLAC
FLAC is a codec which allows digital audio to be losslessly compressed such that file size is reduced without any information being lost...

 datastream
Order within
DTS/AAC
Advanced Audio Coding
Advanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....

Channel name Color-coding on commercial receiver and cabling
0 1 Front left White
1 2 Front right Red
2 0 Center Green
3 5 Low frequency Purple
4 3 Surround left Blue
5 4 Surround right Grey
6 6 Surround back left Brown
7 7 Surround back right Khaki

Front left Center Front right
Surround left Surround right
Surround back left Surround back right
Low frequency

Sonic Whole Overhead Sound

In 2002, Dolby premiered a master of We Were Soldiers
We Were Soldiers
We Were Soldiers is a 2002 American war film that dramatizes the Battle of Ia Drang on November 14, 1965. The film was directed by Randall Wallace and stars Mel Gibson. It is based on the book We Were Soldiers Once… And Young by Lieutenant General Hal Moore and reporter Joseph L...

 which featured a Sonic Whole Overhead Sound soundtrack. This mix included a new ceiling-mounted height channel.

Ambisonics

Ambisonics is a series of recording and replay techniques using multichannel mixing technology that can be used live or in the studio and which recreates the soundfield as it existed in the space, in contract to traditional surround systems, which can only create illusion of the soundfield if the listener is located in a very narrow sweetspot between speakers. Any number of speakers in any physical arrangement can be used to recreate a sound field. With 6 or more speakers arranged around a listener, a 3-dimensional ("periphonic", or full-sphere) sound field can be presented. Ambisonics was invented by Michael Gerzon.

Panor-Ambiophonic (PanAmbio) 4.0/4.1

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. Four channel recordings, especially those containing binaural cues, create speaker-binaural surround sound. 5.1 channel recordings, including movie DVDs, are compatible by mixing C-channel content to the front speaker pair. 6.1 can be played by mixing SC to the back pair.

Standard speaker channels

Channel name Identifier Index Flag 1.0 Mono* 2.0 Stereo** 2.1 Stereo** 4.1 Surround 4.0 Quad 4.1 5.1 5.1 Side*** 6.1 7.1 Front 7.1 Surround 9.1 Surround
Front Left SPEAKER_FRONT_LEFT 0 0x00000001
Front Right SPEAKER_FRONT_RIGHT 1 0x00000002
Front Center SPEAKER_FRONT_CENTER 2 0x00000004
Low Frequency (Subwoofer
Subwoofer
A subwoofer is a woofer, or a complete loudspeaker, which is dedicated to the reproduction of low-pitched audio frequencies known as the "bass". The typical frequency range for a subwoofer is about 20–200 Hz for consumer products, below 100 Hz for professional live sound, and below...

)
SPEAKER_LOW_FREQUENCY 3 0x00000008
Back Left SPEAKER_BACK_LEFT 4 0x00000010
Back Right SPEAKER_BACK_RIGHT 5 0x00000020
Front Left of Center SPEAKER_FRONT_LEFT_OF_CENTER 6 0x00000040
Front Right of Center SPEAKER_FRONT_RIGHT_OF_CENTER 7 0x00000080
Back Center SPEAKER_BACK_CENTER 8 0x00000100
Side Left SPEAKER_SIDE_LEFT 9 0x00000200
Side Right SPEAKER_SIDE_RIGHT 10 0x00000400
Front Left Height SPEAKER_LEFT_HEIGHT 12 0x00001000
Front Right Height SPEAKER_RIGHT_HEIGHT 14 0x00004000


The table above shows the various speaker configurations that are commonly used for end-user equipment. The order and identifiers are those specified for the channel mask in the standard uncompressed WAV
WAV
Waveform Audio File Format , is a Microsoft and IBM audio file format standard for storing an audio bitstream on PCs...

 file format (which contains a raw multichannel PCM stream) and are used according to the same specification for most PC connectible digital sound hardware and PC operating systems capable of handling multiple channels. While it is certainly possible to build any speaker configuration, there isn't a lot of commercially available movie or music content for alternative speaker configurations. Such cases, however, can be worked around by remixing the source content channels to the speaker channels using a matrix table specifying how much of each content channel is played through each speaker channel

(*) For historical reasons, when using (1.0) mono sound, often in technical implementations the first (left) channel is used, instead of the center speaker channel, in many other cases when playing back multi-channel content on a device with a mono speaker configuration all channels are downmixed into one channel. The way standard mono and stereo plugs used for common audio devices are designed ensures this as well.

(**) Stereo (2.0) is still the most common format for music, as most computers, television sets and portable audio players only feature two speakers, and the red book Audio CD standard used for retail distribution of music only allows for 2 channels. A 2.1 speaker set does generally not have a separate physical channel for the low frequency effects, as the speaker set downmixes the low frequency components of the two stereo channels into one channel for the subwoofer.

(***) This is the correct speaker placement for 5.1 sound reproduction from Dolby and DTS systems.

10.2 Channel Surround

10.2 is the surround sound format developed by THX
THX
THX is a trade name of a high-fidelity audio/visual reproduction standard for movie theaters, screening rooms, home theaters, computer speakers, gaming consoles, and car audio systems. The current THX was created in 2001 when it spun off from Lucasfilm Ltd...

 creator Tomlinson Holman
Tomlinson Holman
Tomlinson M. Holman is an American film theorist, audio engineer, and inventor of film technologies, notably the Lucasfilm THX sound system. He developed the world's first 10.2 sound system. Earlier, Holman developed what was known as the Holman Preamplifier, for the Apt Corporation. He holds a...

 of TMH Labs and University of Southern California
University of Southern California
The University of Southern California is a private, not-for-profit, nonsectarian, research university located in Los Angeles, California, United States. USC was founded in 1880, making it California's oldest private research university...

 (schools of Cinema/Television and Engineering). Developed along with Chris Kyriakakis of the USC Viterbi School of Engineering
Viterbi School of Engineering
The Viterbi School of Engineering is located at the University of Southern California in the United States. It was renamed following a $52 million donation by Andrew Viterbi...

, 10.2 refers to the format's promotional slogan: "Twice as good as 5.1". Advocates of 10.2 argue that it is the audio equivalent of IMAX
IMAX
IMAX is a motion picture film format and a set of proprietary cinema projection standards created by the Canadian company IMAX Corporation. IMAX has the capacity to record and display images of far greater size and resolution than conventional film systems...

.

10.2 augments the LS (left surround) and RS (right surround) channels by two point surround channels that can more finely manipulate sound—allowing the mixer to shift sounds in a distinct 360° circle around the movie watcher. 10.2 is also used to refer to 12.2 which uses five front and five surround channels, where 10.2 uses five front and three surround channels. The difference is not the placement of the speakers but rather the type of speakers and the information sent to it/them. 12.2 would use surround diffuse channels (L+R) and surround direct (L+R) channels. The diffuse channels would use dipole speakers and be used for ambient effects common in movies. The surround direct would use standard monopole speakers and be use to emit sound directly to the listener, optimal for surround sound music.

The 14 discrete channels are:
  • Five front speakers: Left Wide, Left, Center, Right and Right Wide
  • Five surround channels: Left Surround Diffuse, Left Surround Direct, Back Surround, Right Surround Diffuse and Right Surround Direct
  • Two LFE channels: LFE Left, LFE Right
  • Two Height channels: Left Height, Right Height


The .2 of the 10.2 refers to the addition of a second subwoofer. The system is bass managed such that all the speakers on the left side use the left sub and all the speakers on the right use the right sub. The Center and Back Surround speaker are split between the two subs. The two subs also serve as two discrete LFE (Low Frequency Effects) channels. Although low frequencies are not easily localizable, it was found that splitting the bass on either side of the audience increases the sense of envelopment.

22.2 Channel Surround

22.2 is the surround sound component of Ultra High Definition Television, and has been developed by NHK Science & Technical Research Laboratories. As its name suggests, it uses 24 speakers. These are arranged in three layers: A middle layer of ten speakers, an upper layer of nine speakers, and a lower layer of three speakers and two sub-woofers. The system was demonstrated at Expo 2005
Expo 2005
Expo 2005 was the World's Fair held for 185 days between Friday, March 25 and Sunday, September 25, 2005, in Aichi Prefecture, Japan, east of the city of Nagoya. It was a Specialized International Exhibition under the scheme of the 1972 protocol of the Convention relating to International Exhibitions...

, Aichi, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, the NAB Shows 2006 and 2009, Las Vegas
Las Vegas metropolitan area
The Las Vegas Valley is the heart of the Las Vegas-Paradise, NV MSA also known as the Las Vegas–Paradise–Henderson MSA which includes all of Clark County, Nevada, and is a metropolitan area in the southern part of the U.S. state of Nevada. The Valley is defined by the Las Vegas Valley landform, a ...

, and the IBC
International Broadcasting Convention
The International Broadcasting Convention, more commonly known by its acronym IBC, is an annual trade show for broadcasters, content creators/providers, equipment manufacturers, professional and technical associations, and other participants in the Broadcasting industry...

 trade shows 2006 and 2008, Amsterdam
Amsterdam
Amsterdam is the largest city and the capital of the Netherlands. The current position of Amsterdam as capital city of the Kingdom of the Netherlands is governed by the constitution of August 24, 1815 and its successors. Amsterdam has a population of 783,364 within city limits, an urban population...

, Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

.

See also

  • 3D audio effect
    3D audio effect
    3D audio effects are a group of sound effects that attempt to widen the stereo image produced by two loudspeakers or stereo headphones, or to create the illusion of sound sources placed anywhere in 3 dimensional space, including behind, above or below the listener.There are several types of 3D...

  • 5.1 surround sound
    5.1 surround sound
    5.1 is the common name for six channel surround sound multichannel audio systems. 5.1 is now the most commonly used layout in both commercial cinemas and home theaters. It uses five full bandwidth channels and one low frequency enhancement channel . Dolby Digital, Dolby Pro Logic II, DTS, and...

  • 7.1 surround sound
  • Ambisonics
    Ambisonics
    Ambisonics is a series of recording and replay techniques using multichannel mixing technology that can be used live or in the studio. By encoding and decoding sound information on a number of channels, a 2-dimensional or 3-dimensional sound field can be presented...

     - Surround sound techniques
  • Aurophonie - 3D surround sound
  • Bass management
    Bass management
    The fundamental principle of bass management in surround sound replay systems is that bass content in the incoming signal, irrespective of channel, should be directed only to loudspeakers capable of handling it, whether the latter are the main system loudspeakers or one or more special...

  • Dolby Surround
    Dolby Surround
    Dolby Surround was the earliest consumer version of Dolby's multichannel analog film sound decoding format Dolby Stereo introduced to the public in 1982 during the time home video recording formats were introducing Stereo and HiFi capability...

  • DTS (sound system)
  • DVD Audio
  • Four channel compact disc digital audio
  • Haas effect
    Haas effect
    The Haas effect is a psychoacoustic effect, described in 1949 by Helmut Haas in his Ph.D. thesis. It is often equated with the underlying precedence effect .- Experiments and findings :...

  • Holophonics
    Holophonics
    Holophonics is a binaural recording system created by Hugo Zuccarelli that is claimed to be based on the claim that the auditory system acts as an interferometer. The sound characteristics of Holophonics are most clearly heard through headphones, though can be demonstrated to be effective with 2...

  • Iosono
    Iosono
    Iosono is the product name of an audio system presented by the Fraunhofer Institute and the Iosono GmbH in 2004. It is based on wave field synthesis, a method to use secondary audio sources to recreate primary wave fields, that was developed at Delft University of Technology in the Netherlands in...

  • Matrix Decoder
    Matrix decoder
    Matrix decoder is an audio technology where a finite number of discrete audio channels are decoded into a larger number of channels on play back...

  • MP3 Surround
    MP3 Surround
    MP3 Surround is an extension of MP3 for multi-channel audio support including 5.1 surround sound. It was developed by Fraunhofer IIS in collaboration with Thomson and Agere Systems, and released in December 2004....

  • MPEG Surround
    MPEG Surround
    MPEG Surround , also known as Spatial Audio Coding is a lossy compression format for surround sound that provides a method for extending mono or stereo audio services to multi-channel audio in a backwards compatible fashion...

  • Penteo
    Penteo
    Penteo is a digital audio, stereo-to-5.1 surround conversion process based on a mashup of Avery Lee's open source Center Cut algorithm from VirtualDub combined with Hans Van Zutphen's freeware Tape Restore Live azimuth corrector...

     - Convert stereo to surround
  • Precedence effect
    Precedence effect
    The precedence effect or law of the first wavefront is a binaural psychoacoustic effect. It means: If the same sound signal arrives time delayed at a listener from different directions, only the direction of the first arriving sound signal is perceived...

  • Quadraphonic
    Quadraphonic
    Quadraphonic sound – the most widely used early term for what is now called 4.0 surround sound – uses four channels in which speakers are positioned at the four corners of the listening space, reproducing signals that are independent of one another...

  • Soundfield microphone
    Soundfield microphone
    The Soundfield microphone is an audio microphone composed of four closely spaced subcardioid or cardioid microphone capsules arranged in a tetrahedron. It was invented by Michael Gerzon and Peter Craven, and is a part of, but not exclusive to, Ambisonics, a surround sound technology...

  • Super Audio CD
    Super Audio CD
    Super Audio CD is a high-resolution, read-only optical disc for audio storage. Sony and Philips Electronics jointly developed the technology, and publicized it in 1999. It is designated as the Scarlet Book standard. Sony and Philips previously collaborated to define the Compact Disc standard...

  • Virtual surround
    Virtual surround
    Virtual surround is an audio system which attempts to create the perception that there are many more sources of sound than are actually present. In order to achieve this it is necessary to devise some means of tricking the human auditory system into thinking that a sound is coming from somewhere...

  • Wave field synthesis
    Wave field synthesis
    Wave field synthesis is a spatial audio rendering technique, characterized by creation of virtual acoustic environments. It produces "artificial" wave fronts synthesized by a large number of individually driven speakers. Such wave fronts seem to originate from a virtual starting point, the virtual...


External links

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