thumb|12.2 channel surround sound (7 front, 4 sides, 1 back, 2 bass)
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.
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.
History
The first documented use of surround sound was in 1940, for Disney's animated film Fantasia. Walt Disney was inspired by Nikolai Rimsky-Korsakov's operatic piece Flight of the Bumblebee to have a bumblebee featured in his musical Fantasia and also sound as if it was flying in all parts of the theatre. The initial multichannel audio application was called 'Fantasound', comprising three audio channels and speakers. The sound was diffused throughout the cinema, controlled by an engineer using some 54 loudspeakers. The surround sound was achieved using the sum and the difference of the phase of the sound. However, this experimental use of surround sound was excluded from the film in later showings. In 1952, surround sound successfully reappeared with the film "This is Cinerama", using discrete seven-channel sound, and the race to develop other surround sound methods took off. For the release of the 1953 20th Century Fox film The Robe, the studio felt the film needed a larger soundstage to match its wider CinemaScope presentation and released it with four-track magnetic stereo sound with left, right, center and mono surround channels.
In the 1950s, the German composer Karlheinz Stockhausen experimented with and produced ground-breaking electronic compositions such as Gesang der Jünglinge and Kontakte, the latter using fully discrete and rotating quadraphonic sounds generated with industrial electronic equipment in Herbert Eimert's studio at the Westdeutscher Rundfunk (WDR). Edgar Varese's Poème électronique, created for the Iannis Xenakis-designed Philips Pavilion at the 1958 Brussels World's Fair, also used spatial audio with 425 loudspeakers used to move sound throughout the pavilion.
In 1957, working with artist Jordan Belson, Henry Jacobs produced Vortex: Experiments in Sound and Light - a series of concerts featuring new music, including some of Jacobs' own, and that of Karlheinz Stockhausen, and many others - taking place in the Morrison Planetarium in Golden Gate Park, San Francisco. Sound designers commonly regard this as the origin of the (now standard) concept of surround sound. The program was popular, and Jacobs and Belson were invited to reproduce it at the 1958 World Expo in Brussels.
There are also many other composers who created ground-breaking surround sound works in the same time period.
In 1978, a concept devised by Max Bell for Dolby Laboratories called split surround was tested with the movie Superman. This led to the 70mm stereo surround release of Apocalypse Now, which became one of the first formal releases in cinemas with three channels in the front and two in the rear. There were typically five speakers behind the screens of 70mm-capable cinemas, but only the left, center and right were used full-frequency, while center-left and center-right were only used for bass-frequencies (as it is currently common). The Apocalypse Now encoder/decoder was designed by Michael Karagosian, also for Dolby Laboratories. The surround mix was produced by an Oscar-winning crew led by Walter Murch for American Zoetrope. The format was also deployed in 1982 with the stereo surround release of Blade Runner.
The 5.1 version of surround sound originated in 1987 at the famous French Cabaret Moulin Rouge. A French engineer, Dominique Bertrand, used a mixing board specially designed in cooperation with Solid State Logic, based on the 5000 series and including six channels. Respectively: A left, B right, C center, 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, Senegal.
Creating surround sound
Surround sound is created in several ways. 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—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 methods to simulate a two-dimensional (2-D) sound field with headphones. A third approach, based on Huygens' principle, attempts to reconstruct the recorded sound field wavefronts within the listening space; an audio hologram form. One form, wave field synthesis (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 4th approach is using three mics, one for front, one for side and one for rear, also called Double MS recording.
The Ambisonics form, also based on Huygens' principle, gives an exact sound reconstruction at the central point; however, it is less accurate away from the central point. 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. Moreover, Ambisonics products are the standard in surround sound hardware sold by Meridian Audio. 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 can also be achieved by mastering level, from stereophonic sources as with Penteo and NUGEN Audio, which uses digital 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. However, there are more ways to create surround sound out of stereo, for instance, with the routines based on QS and SQ for encoding Quad sound, where instruments were divided over 4 speakers in the studio. This way of creating surround with software routines is normally referred to as upmixing, which was particularly successful on the Sansui QSD-series decoders that had a mode where it mapped the L ↔ R stereo onto an ∩ arc.
Standard configurations
There are many alternative setups available for a surround sound experience, with a 3-2 (3 front, 2 back speakers and a low-frequency effects channel) configuration (more commonly referred to as 5.1 surround) being the standard for most surround sound applications, including cinema, television and consumer applications. This is a compromise between the ideal image creation of a room and that of practicality and compatibility with two-channel stereo. Because most surround sound mixes are produced for 5.1 surround (6 channels), larger setups require matrixes or processors to feed the additional speakers. The ITU standard also allows for additional surround speakers, which need to be distributed evenly between 60 and 150 degrees. 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. Specialised techniques have therefore been developed for 3-channel stereo. Surround microphone techniques largely depend on the setup used, therefore being biased towards the 5.1 surround setup, as this is the standard.
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, given loudspeakers that have low-frequency response to 30 Hz, 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. The label BIS Records generally uses a 5.0 channel mix.
Channel notation
Channel notation indicates the number of discrete channels encoded in the audio signal, not necessarily the number of channels reproduced for playback. The number of playback channels can be increased by using matrix decoding. The number of playback channels may also differ from the number of speakers used to reproduce them if one or more channels drive a group of speakers. Notation represents the number of channels, not the number of speakers.
The first digit in 5.1 is the number of full-range channels. The .1 reflects the limited frequency range of the LFE channel.
For example, two stereo speakers with no LFE channel = 2.0
<br/>
5 full-range channels + 1 LFE channel = 5.1
An alternative notation shows 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, with a decimal point marking the number of limited-range LFE channels.
E.g. 3 front channels + 2 side channels + an LFE channel = 3/2.1
The notation can be expanded to include Matrix Decoders. Dolby Digital EX, for example, has a sixth full-range channel incorporated into the two rear channels with a matrix. This is expressed:
3 front channels + 2 rear channels + 3 channels reproduced in the rear in total + 1 LFE channel = 3/2:3.1
The term stereo, although popularised in reference to two-channel audio, historically also referred to surround sound, as it strictly means solid (three-dimensional) sound. However, this is no longer common usage, and stereo sound almost exclusively means two channels, left and right.
Channel identification
In accordance with ANSI/CEA-863-A
:{|class="wikitable sortable"
|+ANSI/CEA-863-A identification for surround sound channels
! colspan=3 | Zero-based channel index
! rowspan=2 | Channel name
! rowspan=2 colspan=2 | Color-coding on commercial<br/>receiver and cabling
|-
! MP3/WAV/FLAC<br>
! DTS/AAC<br>
! Vorbis/Opus<br>
|-
|0
|1
|0
|Front left
|style="background:white"| ||White
|-
|1
|2
|2
|Front right
|style="background:red"| ||Red
|-
|2
|0
|1
|Center
|style="background:green"| ||Green
|-
|3
|5
|7
|Subwoofer
|style="background:purple"| ||Purple
|-
|4
|3
|3
|Side left
|style="background:blue"| ||Blue
|-
|5
|4
|4
|Side right
|style="background:gray"| ||Grey
|-
|6
|6
|5
|Rear left
|style="background:brown"| ||Brown
|-
|7
|7
|6
|Rear right
|style="background:khaki"| ||Khaki
|}
:::{|class="wikitable"
|+Diagram
|style="background:white;color:black"|Front left
|style="background:green;color:white"|Center
|style="background:red;text-align:right;color:white"|Front right
|-
|style="background:blue;color:white"|Side left
|style="text-align:center;font-size:200%;" rowspan="2"| 40px
|style="background:gray;text-align:right;color:black"|Side right
|-
|style="background:brown;color:white"|Rear left
|style="background:khaki;text-align:right;color:black"|Rear right
|-
|style="background:purple;text-align:center;color:white" colspan="3"|Subwoofer
|}
:{|class="wikitable"
|+Height channels
!Index
!Channel name
!colspan=2|Color-coding on commercial<br/>receiver and cabling
|-
|8
|Left height 1
|style="background:yellow"| ||Yellow
|-
|9
|Right height 1
|style="background:orange"| ||Orange
|-
|10
|Left height 2
|style="background:pink"| ||Pink
|-
|11
|Right height 2
|style="background:magenta"| ||Magenta
|}
Sonic Whole Overhead Sound
In 2002, Dolby premiered a master of We Were Soldiers which featured a Sonic Whole Overhead Sound soundtrack. This mix included a new ceiling-mounted height channel.
Ambisonics
Ambisonics is a recording and playback technique using multichannel mixing that can be used live or in the studio and which recreates the sound field as it existed in the space, in contrast to traditional surround systems, which can only create the illusion of the sound field if the listener is located in a very narrow sweet spot 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.
Binaural recording
Binaural recording is a method of recording sound that uses two microphones, arranged with the intent to create the 3-D stereo experience of being present in the room with the performers or instruments. The idea of a three dimensional or internal form of sound has developed into technology for stethoscopes, creating in-head acoustics and IMAX movies, creating a three-dimensional acoustic experience.
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
Several speaker configurations are commonly used for consumer equipment. The order and identifiers are those specified for the channel mask in the standard uncompressed WAV 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.
{|class="wikitable"
|+ Standard speaker channels in Microsoft Windows WDM Audio driver model
|-
! Channel name !! ID !! Identifier !! Index !! Flag
|-
! Front Left
| FL || SPEAKER_FRONT_LEFT
| 0 || 0x00000001
|-
!Front Right
| FR || SPEAKER_FRONT_RIGHT
| 1 || 0x00000002
|-
! Front Center
| FC || SPEAKER_FRONT_CENTER
| 2 || 0x00000004
|-
!title="Subwoofer"| Low Frequency
| LFE || SPEAKER_LOW_FREQUENCY
| 3 || 0x00000008
|-
! Back Left
| BL || SPEAKER_BACK_LEFT
| 4 || 0x00000010
|-
! Back Right
| BR || SPEAKER_BACK_RIGHT
| 5 || 0x00000020
|-
! Front Left of Center
| FLC || SPEAKER_FRONT_LEFT_OF_CENTER
| 6 || 0x00000040
|-
! Front Right of Center
| FRC || SPEAKER_FRONT_RIGHT_OF_CENTER
| 7 || 0x00000080
|-
! Back Center
| BC || SPEAKER_BACK_CENTER
| 8 || 0x00000100
|-
! Side Left
| SL || SPEAKER_SIDE_LEFT
| 9 || 0x00000200
|-
! Side Right
| SR || SPEAKER_SIDE_RIGHT
| 10 || 0x00000400
|-
! Top Center
| TC || SPEAKER_TOP_CENTER
| 11 || 0x00000800
|-
! Front Left Height
| TFL || SPEAKER_TOP_FRONT_LEFT
| 12 || 0x00001000
|-
! Front Center Height
| TFC || SPEAKER_TOP_FRONT_CENTER
| 13 || 0x00002000
|-
! Front Right Height
| TFR || SPEAKER_TOP_FRONT_RIGHT
| 14 || 0x00004000
|-
! Rear Left Height
| TBL || SPEAKER_TOP_BACK_LEFT
| 15 || 0x00008000
|-
! Rear Center Height
| TBC || SPEAKER_TOP_BACK_CENTER
| 16 || 0x00010000
|-
! Rear Right Height
| TBR || SPEAKER_TOP_BACK_RIGHT
| 17 || 0x00020000
|}
While it is possible to build any speaker configuration, there is little commercial movie or music content for alternative speaker configurations. However, source channels can be remixed for the speaker channels using a matrix table specifying how much of each content channel is played through each speaker channel.
Most channel configurations may include an LFE channel (the channel played through the subwoofer.) This makes the configuration .1 instead of .0. Most modern multichannel mixes contain one LFE; some use two.
{| class="wikitable sortable"
|+ Standard speaker channel layouts
!rowspan=2| Icon !!rowspan=2| System !!rowspan=2| Channels !!rowspan=2| LFE
!colspan=4| Front !!colspan=1| Sides !!colspan=3 title="Rear"| Back
|-
! FL+FR || FC || FLC+FRC || TFL+TFR
! SL+SR || BL+BR || BC || TBL+TBR
|-
| resize|30px
! Mono
| 1.0 ||
| || || ||
| || || ||
|-
| resize|30px
! Stereo
| 2.0 ||
| || || ||
| || || ||
|-
| resize|30px
! Stereo
| 3.0 ||
| || || ||
| || || ||
|-
| resize|30px
! Surround
| 3.0 ||
| || || ||
| || || ||
|-
| resize|30px
! Quad
| 4.0 ||
| || || ||
| || || ||
|-
| resize|30px
! Side Quad
| 4.0 ||
| || || ||
| || || ||
|-
| resize|30px<!--3 0-1 channels (muse laserdisc) label.svg-->
! Surround
| 4.0 ||
| || || ||
| || || ||
|-
| resize|30px<!--5 0 channels (surround sound) label.svg-->
! (Front)
| 5.0 ||
| || || ||
| || || ||
|-
| resize|30px
! Side
| 5.0 ||
| || || ||
| || || ||
|-
| resize|30px
! Atmos
|title="9.1"| 5.1.4 ||
| || || ||
| || || ||
|-
| resize|30px
! Hexagonal (Back)
| 6.0 ||
| || || ||
| || || ||
|-
|
! Front
| 6.0 ||
| || || ||
| || || ||
|-
| resize|30px
! (Side)
| 6.0 ||
| || || ||
| || || ||
|-
| resize|30px
! Wide
| 7.1 ||
| || || ||
| || || ||
|-
| resize|30px
!title="Front / Wide-Side"| Side
| 7.0 ||
| || || ||
| || || ||
|-
| resize|30px
! Surround
7.1.2/7.1.4 immersive sound
7.1.2 and 7.1.4 immersive sound, along with 5.1.2 and 5.1.4 formats, add either 2 or 4 overhead speakers to enable sound objects and special effect sounds to be panned overhead for the listener. Introduced for theatrical film releases in 2012 by Dolby Laboratories under the trademark name Dolby Atmos.
Dolby Atmos (and other Microsoft Spatial Sound engines; see in ) additionally support a virtual 8.1.4.4 configuration, to be rendered by a HRTF. The configuration adds to 7.1.4 with a center speaker behind the listener and 4 speakers below.
10.2 surround sound
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". Advocates of 10.2 argue that it is the audio equivalent of IMAX.
11.1 surround sound
11.1 sound is supported by BARCO with installations in theaters worldwide.
22.2 surround sound
22.2 is the surround sound component of Ultra High Definition Television, 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, Aichi, Japan, the NAB Shows 2006 and 2009, Las Vegas, and the IBC trade shows 2006 and 2008, Amsterdam, Netherlands.
See also
- 3D audio effect
- Binaural recording
- Dolby Surround
- Duophonic
- Four-channel Compact Disc Digital Audio
- Holophonics
- MPEG Surround
- Precedence effect
- Soundfield microphone
- Virtual surround