Surround sound is a technique for enriching the fidelity and depth of
sound reproduction
Sound recording and reproduction is the electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording ...
by using multiple
audio channel
An audio signal is a representation of sound, typically using either a changing level of electrical voltage for analog signals, or a series of binary numbers for digital signals. Audio signals have frequencies in the audio frequency range of roug ...
s from
speaker
Speaker may refer to:
Society and politics
* Speaker (politics), the presiding officer in a legislative assembly
* Public speaker, one who gives a speech or lecture
* A person producing speech: the producer of a given utterance, especially:
** I ...
s that surround the listener (
surround channels). Its first application was in
movie theater
A movie theater (American English), cinema (British English), or cinema hall ( Indian English), also known as a movie house, picture house, the movies, the pictures, picture theater, the silver screen, the big screen, or simply theater is a ...
s. Prior to surround sound, theater sound systems commonly had three ''screen channels'' of sound that played from three
loudspeaker
A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or ...
s (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
Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous system ...
of sound spatialization by exploiting
sound localization
Sound localization is a listener's ability to identify the location or origin of a detected sound in direction and distance.
The sound localization mechanisms of the mammalian auditory system have been extensively studied. The auditory system us ...
: 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
loudspeaker
A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or ...
s. 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
The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...
'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
A subwoofer (or sub) is a loudspeaker designed to reproduce low-pitched audio frequencies known as bass and sub-bass, lower in frequency than those which can be (optimally) generated by a woofer. The typical frequency range for a subwoofer i ...
, 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 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
Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertisin ...
, 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
Broadcasting is the distribution of audio or video content to a dispersed audience via any electronic mass communications medium, but typically one using the electromagnetic spectrum ( radio waves), in a one-to-many model. Broadcasting beg ...
; for a
film, specific techniques are adapted to
movie theater
A movie theater (American English), cinema (British English), or cinema hall ( Indian English), also known as a movie house, picture house, the movies, the pictures, picture theater, the silver screen, the big screen, or simply theater is a ...
or to home (e.g.,
home cinema
Home cinema, also called home theaters or theater rooms, are home entertainment audio-visual systems that seek to reproduce a movie theater experience and mood using consumer electronics-grade video and audio equipment that is set up in a room ...
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
Situational awareness or situation awareness (SA) is the perception of environmental elements and events with respect to time or space, the comprehension of their meaning, and the projection of their future status. An alternative definition is tha ...
in military and public safety application.
Types of media and technologies
Commercial surround sound media include videocassettes,
DVDs
The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any kind ...
, and
SDTV
Standard-definition television (SDTV, SD, often shortened to standard definition) is a television system which uses a resolution that is not considered to be either high or enhanced definition. "Standard" refers to it being the prevailing sp ...
broadcasts encoded as
compressed Dolby Digital and
DTS, and
lossless audio
In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compressio ...
such as
DTS HD Master Audio
DTS-HD Master Audio (DTS-HD MA; known as DTS++ before 2004) is a multi-channel, lossless audio codec developed by DTS as an extension of the lossy DTS Coherent Acoustics codec (DTS CA; usually itself referred to as just DTS). Rather than being ...
and
Dolby TrueHD
Dolby TrueHD is a lossless, multi-channel audio codec developed by Dolby Laboratories for home video, used principally in Blu-ray Disc and compatible hardware. Dolby TrueHD, along with Dolby Digital Plus (E-AC-3) and Dolby AC-4, is one of the i ...
on
HDTV
High-definition television (HD or HDTV) describes a television system which provides a substantially higher image resolution than the previous generation of technologies. The term has been used since 1936; in more recent times, it refers to the g ...
Blu-ray Disc and
HD DVD
HD DVD (short for High Definition Digital Versatile Disc) is an obsolete high-density optical disc format for storing data and playback of high-definition video. Supported principally by Toshiba, HD DVD was envisioned to be the successor to the ...
, which are identical to the studio master. Other commercial formats include the competing
DVD-Audio
DVD-Audio (commonly abbreviated as DVD-A) is a digital format for delivering high-fidelity audio content on a DVD. DVD-Audio uses most of the storage on the disc for high-quality audio and is not intended to be a video delivery format.
The st ...
(DVD-A) and
Super Audio CD
Super Audio CD (SACD) is an optical disc format for audio storage introduced in 1999. It was developed jointly by Sony and Philips Electronics and intended to be the successor to the Compact Disc (CD) format.
The SACD format allows multiple a ...
(SACD) formats, and
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.
MP3 Surround is backward comp ...
. Cinema
5.1 surround formats include
Dolby Digital 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
The low-frequency effects (LFE) channel is a band-limited audio track that is used for reproducing deep and intense low-frequency sounds in the 3–120 Hz frequency range.
This track is normally sent to a subwoofer—a loudspeaker des ...
channel. Traditional
7.1
7.1 surround sound is the common name for an eight-channel surround audio system commonly used in home theatre configurations. It adds two additional speakers to the more conventional six-channel (5.1) audio configuration. As with 5.1 surround sou ...
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
A camcorder is a self-contained portable electronic device with video and recording as its primary function. It is typically equipped with an articulating screen mounted on the left side, a belt to facilitate holding on the right side, hot-swa ...
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 (or quadrophonic and sometimes quadrasonic) sound – equivalent to what is now called 4.0 surround sound – uses four audio channels in which speakers are positioned at the four corners of a listening space. The system allows for th ...
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 card
A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term ''sound card'' is also applied to external audio ...
s contain integral
digital signal processors or digital audio processors to simulate surround sound from a stereophonic source (see
fake stereo
Duophonic sound was a trade name for a type of audio signal processing used by Capitol Records on certain releases and re-releases of mono recordings issued during the 1960s and 1970s. In this process monaural recordings were reprocessed into a ...
).
In 1967, the rock group
Pink Floyd performed the first-ever surround sound concert at "Games for May", a lavish affair at
London
London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...
’s
Queen Elizabeth Hall where the band debuted its custom-made
quadraphonic
Quadraphonic (or quadrophonic and sometimes quadrasonic) sound – equivalent to what is now called 4.0 surround sound – uses four audio channels in which speakers are positioned at the four corners of a listening space. The system allows for th ...
speaker system. The control device they had made, the
Azimuth Co-ordinator, is now displayed at London's
Victoria and Albert Museum
The Victoria and Albert Museum (often abbreviated as the V&A) in London is the world's largest museum of applied arts, decorative arts and design, housing a permanent collection of over 2.27 million objects. It was founded in 1852 and nam ...
, 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 International Film Festival (also known as Fantasia-fest, FanTasia, and Fant-Asia) is a film festival that has been based mainly in Montreal since its founding in 1996. Regularly held in July of each year, it is valued by both hardcore ...
''.
Walt Disney
Walter Elias Disney (; December 5, 1901December 15, 1966) was an American animator, film producer and entrepreneur. A pioneer of the American animation industry, he introduced several developments in the production of cartoons. As a film p ...
was inspired by
Nikolai Rimsky-Korsakov's operatic piece ''
Flight of the Bumblebee'' to have a
bumblebee
A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus ''Bombus'', part of Apidae, one of the bee families. This genus is the only extant group in the tribe Bombini, though a few extinct related genera ...
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
Fantasound was a reproduction system developed by engineers of Walt Disney studios and RCA for Walt Disney's animated film ''Fantasia'', the first commercial film released in stereo.
Origins
Walt Disney's cartoon character Mickey Mouse entered ...
', 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.
In the 1950s, the German composer
Karlheinz Stockhausen
Karlheinz Stockhausen (; 22 August 1928 – 5 December 2007) was a German composer, widely acknowledged by critics as one of the most important but also controversial composers of the 20th-century classical music, 20th and early 21st-century ...
experimented with and produced ground-breaking electronic compositions such as ''
Gesang der Jünglinge
''Gesang der Jünglinge'' (literally "Song of the Youths") is an 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. The vo ...
'' and ''
Kontakte
''Kontakte'' ("Contacts") is an electronic music work by Karlheinz Stockhausen, realized in 1958–60 at the ''Westdeutscher Rundfunk'' (WDR) electronic-music studio in Cologne with the assistance of Gottfried Michael Koenig. The score is Nr. 12 ...
'', the latter using fully discrete and rotating
quadraphonic sounds generated with industrial electronic equipment in
Herbert Eimert Herbert Eimert (8 April 1897 – 15 December 1972) was a German music theorist, musicologist, journalist, music critic, editor, radio producer, and composer.
Education
Herbert Eimert was born in Bad Kreuznach. He studied music theory and compo ...
's studio at the ''
Westdeutscher Rundfunk
Westdeutscher Rundfunk Köln (''West German Broadcasting Cologne''; WDR, ) 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 conso ...
'' (WDR).
Edgar Varese's
Poème électronique
''Poème électronique'' (English Translation: "Electronic Poem") is an 8-minute piece of electronic music by composer Edgard Varèse, written for the Philips Pavilion at the 1958 Brussels World's Fair. The Philips corporation commissioned L ...
, created for the
Iannis Xenakis
Giannis Klearchou Xenakis (also spelled for professional purposes as Yannis or Iannis Xenakis; el, Γιάννης "Ιωάννης" Κλέαρχου Ξενάκης, ; 29 May 1922 – 4 February 2001) was a Romanian-born Greek-French avant-garde c ...
-designed
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 electronics manufacturer Philips, the pavilion was designed to house a multimedia spectacle that celebrated postwar ...
at the 1958
Brussels World's Fair
Expo 58, also known as the 1958 Brussels World's Fair (french: Exposition Universelle et Internationale de Bruxelles de 1958, nl, Brusselse Wereldtentoonstelling van 1958), was a world's fair held on the Heysel/Heizel Plateau in Brussels, Bel ...
, 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
Karlheinz Stockhausen (; 22 August 1928 – 5 December 2007) was a German composer, widely acknowledged by critics as one of the most important but also controversial composers of the 20th-century classical music, 20th and early 21st-century ...
, 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 that 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
Superman is a superhero who appears in American comic books published by DC Comics. The character was created by writer Jerry Siegel and artist Joe Shuster, and debuted in the comic book ''Action Comics'' #1 (cover-dated June 1938 and publi ...
''. This led to the 70mm stereo surround release of ''
Apocalypse Now
''Apocalypse Now'' is a 1979 American epic war film produced and directed by Francis Ford Coppola. The screenplay, co-written by Coppola, John Milius and Michael Herr, is loosely based on the 1899 novella '' Heart of Darkness'' by Joseph ...
'', 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
Walter Scott Murch (born July 12, 1943) is an American film editor, director, writer and sound designer. With a career stretching back to 1969, including work on '' THX 1138'', ''Apocalypse Now'', '' The Godfather I'', '' II'', and '' III'', ''Am ...
for
American Zoetrope
American Zoetrope (also known as Omni Zoetrope from 1977 to 1980 and Zoetrope Studios from 1980 until 1990) is a privately run American film production company, centered in San Francisco, California and founded by Francis Ford Coppola and Georg ...
. The format was also deployed in 1982 with the stereo surround release of ''
Blade Runner
''Blade Runner'' is a 1982 science fiction film directed by Ridley Scott, and written by Hampton Fancher and David Peoples. Starring Harrison Ford, Rutger Hauer, Sean Young, and Edward James Olmos, it is an adaptation of Philip K. Dick' ...
''.
The 5.1 version of surround sound originated in 1987 at the famous French Cabaret
Moulin Rouge
Moulin Rouge (, ; ) is a cabaret in Paris, on Boulevard de Clichy, at Place Blanche, the intersection of, and terminus of Rue Blanche.
In 1889, the Moulin Rouge was co-founded by Charles Zidler and Joseph Oller, who also owned the Paris Ol ...
. A French engineer, Dominique Bertrand used a mixing board specially designed in cooperation with
Solid State Logic
Solid State Logic (SSL) is a British company based in Begbroke, Oxfordshire, England that designs and markets audio mixing consoles, signal processors, and other audio technologies for the post-production, video production, broadcast, sound ...
, based on 5000 series and including six 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 ( ; ; wo, Ndakaaru) (from :wo:daqaar, daqaar ''tamarind''), is the capital city, capital and List of cities in Senegal, largest city of Senegal. The city of Dakar proper has a population of 1,030,594, whereas the population of the 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
Psychoacoustics is the branch of psychophysics involving the scientific study of sound perception and audiology—how humans perceive various sounds. More specifically, it is the branch of science studying the psychological responses associated wit ...
sound localization
Sound localization is a listener's ability to identify the location or origin of a detected sound in direction and distance.
The sound localization mechanisms of the mammalian auditory system have been extensively studied. The auditory system us ...
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 (WFS) is a spatial audio rendering technique, characterized by creation of virtual acoustic environments. It produces ''artificial'' wavefronts synthesized by a large number of individually driven loudspeakers. Such wavef ...
(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
Ambisonics is a ''full-sphere'' surround sound format: in addition to the horizontal plane, it covers sound sources above and below the listener.
Unlike some other multichannel surround formats, its transmission channels do not carry speaker si ...
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
Meridian Audio is a consumer audio and home theatre equipment manufacturer based in the United Kingdom. Bob Stuart and Allen Boothroyd founded the company in 1977 under the name Boothroyd-Stuart. In 1985 the company released a CD player under ...
. 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, 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 standard surround setup consists of three front speakers LCR (left, center and right), two surround speakers LS and RS (left and right surround respectively) and a subwoofer for the Low Frequency Effects (LFE) channel, that is low-pass filtered at 120 Hz. The angles between the speakers have been standardized by the
ITU
The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...
(International Telecommunication Union) recommendation 775 and AES (Audio Engineering Society) as follows: 60 degrees between the L and R channels (allows for two-channel stereo compatibility) with the center speaker directly in front of the listener. The Surround channels are placed 100-120 degrees from the center channel, with the subwoofer's positioning not being critical due to the low directional factor of frequencies below 120 Hz.
The ITU standard also allows for additional surround speakers, that need to be distributed evenly between 60 and 150 degrees.
Surround mixes of more or fewer channels are acceptable, if they are compatible, as described by the ITU-R BS. 775-1,
with 5.1 surround. The 3-1 channel setup (consisting of one monophonic surround channel) is such a case, where both LS and RS are fed by the monophonic signal at an attenuated level of -3 dB.
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.
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.
The centre channel is especially used in films and television, with dialogue primarily feeding the center channel.
The function of the center channel can either be of a monophonic nature (as with dialogue) or it can be used in combination with the left and right channels for true three-channel stereo. Motion Pictures tend to use the center channel for monophonic purposes with stereo being reserved purely for the left and right channels. Surround microphones techniques have however been developed that fully use the potential of three-channel stereo.
In 5.1 surround, phantom images between the front speakers are quite accurate, with images towards the back and especially to the sides being unstable.
The localisation of a virtual source, based on level differences between two loudspeakers to the side of a listener, shows great inconsistency across the standardised 5.1 setup, also being largely affected by movement away from the reference position. 5.1 surround is therefore limited in its ability to convey 3D sound, making the surround channels more appropriate for ambience or effects.
)
7.1 channel surround is another setup, most commonly used in large cinemas, that is compatible with 5.1 surround, though it is not stated in the ITU-standards. 7.1 channel surround adds two additional channels, center-left (CL) and center-right (CR) to the 5.1 surround setup, with the speakers situated 15 degrees off centre from the listener.
This convention is used to cover an increased angle between the front loudspeakers as a product of a larger screen.
Surround microphone techniques
Most 2-channel stereophonic microphone techniques are compatible with a 3-channel setup (LCR), as many of these techniques already contain a center microphone or microphone pair. Microphone techniques for LCR should, however, try to obtain greater channel separation to prevent conflicting phantom images between L/C and L/R for example.
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.
Surround recording techniques can be differentiated into those that use single arrays of microphones placed in close proximity, and those treating front and rear channels with separate arrays.
Close arrays present more accurate phantom images, whereas separate treatment of rear channels is usually used for ambience.
For accurate depiction of an acoustic environment, such as a halls, side reflections are essential. Appropriate microphone techniques should therefore be used, if room impression is important. Although the reproduction of side images are very unstable in the 5.1 surround setup, room impressions can still be accurately presented.
Some microphone techniques used for coverage of three front channels, include double-stereo techniques, INA-3 (Ideal Cardioid Arrangement), the
Decca Tree setup and the OCT (Optimum Cardioid Triangle).
Surround techniques are largely based on 3-channel techniques with additional microphones used for the surround channels. A distinguishing factor for the pickup of the front channels in surround is that less reverberation should be picked up, as the surround microphones will be responsible for the pickup of reverberation.
Cardioid, hypercardioid, or supercardioid polar patterns will therefore often replace omnidirectional polar patterns for surround recordings. To compensate for the lost low-end of directional (pressure gradient) microphones, additional omnidirectional (pressure microphones), exhibiting an extended low-end response, can be added. The microphone's output is usually low-pass filtered.
A simple surround microphone configuration involves the use of a front array in combination with two backward-facing omnidirectional room microphones placed about 10–15 meters away from the front array. If echoes are notable, the front array can be delayed appropriately. Alternatively, backward facing cardioid microphones can be placed closer to the front array for a similar reverberation pickup.
The INA-5 (Ideal Cardioid Arrangement) is a surround microphone array that uses five cardioid microphones resembling the angles of the standardised surround loudspeaker configuration defined by the ITU Rec. 775.
Dimensions between the front three microphone as well as the polar patterns of the microphones can be changed for different pickup angles and ambient response.
This technique therefore allows for great flexibility.
A well established microphone array is the Fukada Tree, which is a modified variant of the Decca Tree stereo technique. The array consists of five spaced cardioid microphones, three front microphones resembling a Decca Tree and two surround microphones. 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 L, R, LS and RS microphones should be placed in a square formation, with L/R and LS/RS angled at 45 degrees and 135 degrees from the center microphone respectively. Spacing between these microphones should be about 1.8 meters. This square formation is responsible for the room impressions. The center channel is placed a meter in front of the L and R channels, producing a strong center image. 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 NHK (Japanese broadcasting company) developed an alternative technique also involving five cardioid microphones. Here a baffle is used for separation between the front left and right channels, which are 30 cm apart.
Outrigger omnidirectional microphones, low-pass filtered at 250 Hz, are spaced 3 meters apart in line with the L and R cardioids. These compensate for the bass roll-off of the cardioid microphones and also add expansiveness.
A 3-meter spaced microphone pair, situated 2–3 meters behind front array, is used for the surround channels.
The centre channel is again placed slightly forward, with the L/R and LS/RS again angled at 45 and 135 degrees respectively.
The OCT-Surround (Optimum Cardioid Triangle-Surround) microphone array is an augmented technique of the stereo OCT technique using the same front array with added surround microphones. The front array is designed for minimum crosstalk, with the front left and right microphones having supercardioid polar patterns and angled at 90 degrees relative to the center microphone.
It is important that high quality small diaphragm microphones are used for the L and R channels to reduce off-axis coloration.
Equalization can also be used to flatten the response of the supercardioid microphones to signals coming in at up to about 30 degrees from the front of the array.
The center channel is placed slightly forward. The surround microphones are backwards facing cardioid microphones, that are placed 40 cm back from the L and R microphones. 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.
Spacing between the L and R microphones can be varied to obtain the required stereo width.
Specialized microphone arrays have been developed for recording purely the ambience of a space. These arrays are used in combination with suitable front arrays, or can be added to above mentioned surround techniques.
The Hamasaki square (also proposed by NHK) is a well established microphone array used for the pickup of hall ambience. Four figure-eight microphones are arranged in a square, ideally placed far away and high up in the hall. Spacing between the microphones should be between 1–3 meters.
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
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. Here, four cardioid microphones, 90 degrees relative to one another, are placed in square formation, separated by 21–25 cm.
The front two microphones should be positioned 45 degrees off axis from the sound source. This technique therefore resembles back to back near-coincident stereo pairs. The microphones outputs are fed to the L, R and LS, RS channels. The disadvantage of this approach is that direct sound pickup is quite significant.
Many recordings do not require pickup of side reflections. For Live Pop music concerts a more appropriate array for the pickup of ambience is the cardioid trapezium.
All four cardioid microphones are backward facing and angled at 60 degrees from one another, therefore similar to a semi-circle. This is effective for the pickup of audience and ambience.
All the above-mentioned microphone arrays take up considerable space, making them quite ineffective for field recordings. In this respect, the double MS (Mid Side) technique is quite advantageous. This array uses back to back cardioid microphones, one facing forward, the other backwards, combined with either one or two figure-eight microphone. Different channels are obtained by sum and difference of the figure-eight and cardioid patterns.
When using only one figure-eight microphone, the double MS technique is extremely compact and therefore also perfectly compatible with monophonic playback. This technique also allows for postproduction changes of the pickup angle.
Bass management
Surround replay systems may make use of ''bass management'', 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
subwoofer
A subwoofer (or sub) is a loudspeaker designed to reproduce low-pitched audio frequencies known as bass and sub-bass, lower in frequency than those which can be (optimally) generated by a woofer. The typical frequency range for a subwoofer i ...
s.
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 channel
Because the
low-frequency effects
The low-frequency effects (LFE) channel is a band-limited audio track that is used for reproducing deep and intense low-frequency sounds in the 3–120 Hz frequency range.
This track is normally sent to a subwoofer—a loudspeaker des ...
(LFE) 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 channel is a source of some confusion in surround sound. 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
Intermodulation (IM) or intermodulation distortion (IMD) is the amplitude modulation of Signal (electrical engineering), signals containing two or more different frequencies, caused by non-linear, nonlinearities or time variance in a system. ...
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
Telarc International Corporation is an American audiophile independent record label founded in 1977 by two classically trained musicians and former teachers, Jack Renner (recording engineer), Jack Renner and Robert Woods (producer), Robert Woods. ...
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 30Hz, 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 drives 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
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 Decoder
Matrix decoding is an audio technology where a small number of discrete audio channels (e.g., 2) are decoded into a larger number of channels on play back (e.g., 5). The channels are generally, but not always, arranged for transmission or recordin ...
s. Dolby Digital EX, for example, has a sixth full-range channel incorporated into the two rear channels with a
matrix
Matrix most commonly refers to:
* ''The Matrix'' (franchise), an American media franchise
** ''The Matrix'', a 1999 science-fiction action film
** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchis ...
. 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
:
:::
:
Sonic Whole Overhead Sound
In 2002, Dolby premiered a master of ''
We Were Soldiers
''We Were Soldiers'' is a 2002 war film written and directed by Randall Wallace and starring Mel Gibson. Based on the book '' We Were Soldiers Once… and Young'' (1992) by Lieutenant General (Ret.) Hal Moore and reporter Joseph L. Galloway, i ...
'' which featured a Sonic Whole Overhead Sound soundtrack. This mix included a new ceiling-mounted
height channel
Height channels are audio channels in surround sound multichannel audio. Height channels are located above the listening area and increase the sound field beyond the horizontal plane.
Two systems that use height channels, Dolby Pro Logic IIz and ...
.
Ambisonics
Ambisonics is a recording and playback technique using multichannel mixing that can be used live or in the studio and which recreates the soundfield as it existed in the space, in contrast 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.
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
Waveform Audio File Format (WAVE, or WAV due to its filename extension; pronounced "wave") is an audio file format standard, developed by IBM and Microsoft, for storing an audio bitstream on PCs. It is the main format used on Microsoft Wind ...
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 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 configuration may include a
low frequency effects (LFE) channel (the channel played through the
subwoofer
A subwoofer (or sub) is a loudspeaker designed to reproduce low-pitched audio frequencies known as bass and sub-bass, lower in frequency than those which can be (optimally) generated by a woofer. The typical frequency range for a subwoofer i ...
.) This makes the configuration ".1" instead of ".0". Most modern multichannel mixes contain one LFE, some use two.
7.1 surround sound
7.1 surround sound
7.1 surround sound is the common name for an eight-channel surround audio system commonly used in home theatre configurations. It adds two additional speakers to the more conventional six-channel (5.1) audio configuration. As with 5.1 surround sou ...
is a popular format in theaters & Home cinema including Blu-rays with Dolby and DTS being major players.
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 format adds 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 is a surround sound technology developed by Dolby Laboratories. It expands on existing surround sound systems by adding height channels, allowing sounds to be interpreted as three-dimensional objects with neither horizontal, nor verti ...
.
10.2 surround sound
10.2 is the surround sound format developed by
THX
THX Ltd. is an American company that develops the eponymous high fidelity audio/visual reproduction standards for movie theaters, screening rooms, home theaters, computer speakers, gaming consoles, car audio systems, and video games. Founded ...
creator
Tomlinson Holman Tomlinson M. Holman (born 1946) is an American film theorist, audio engineer, and inventor of film technologies, notably the Lucasfilm's THX sound system. He developed the world's first 10.2 sound system.Truta, Filip Truta (May 5, 2011)"Apple Hir ...
of TMH Labs and
University of Southern California
, mottoeng = "Let whoever earns the palm bear it"
, religious_affiliation = Nonsectarian—historically Methodist
, established =
, accreditation = WSCUC
, type = Private research university
, academic_affiliations =
, endowment = $8.1 ...
(schools of Cinema/Television and Engineering). Developed along with
Chris Kyriakakis of the
USC Viterbi School of Engineering
The USC Viterbi School of Engineering (formerly the USC School of Engineering) is the engineering school of the University of Southern California. It was renamed following a $52 million donation by Andrew J. Viterbi, co-founder of Qualcomm.
...
, ''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
Ultra-high-definition television (also known as Ultra HD television, Ultra HD, UHDTV, UHD and Super Hi-Vision) today includes 4K UHD and 8K UHD, which are two digital video formats with an aspect ratio of 16:9. These were first proposed by ...
, 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 was a World Expo held for 185 days between Friday, March 25 and Sunday, September 25, 2005, in Aichi Prefecture, Japan, east of the city of Nagoya. Japan has also hosted Expo '70 Osaka (World Expo), Expo '75 Okinawa (Specialised Expo) ...
,
Aichi
is a prefecture of Japan located in the Chūbu region of Honshū. Aichi Prefecture has a population of 7,552,873 () and a geographic area of with a population density of . Aichi Prefecture borders Mie Prefecture to the west, Gifu Prefectu ...
,
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
, the
NAB Show
NAB Show is an annual trade show produced by the National Association of Broadcasters. It takes place in April, and has been held since 1991 at the Las Vegas Convention Center in Las Vegas, Nevada. The show's tagline is "Where Content Comes t ...
s 2006 and 2009,
Las Vegas
Las Vegas (; Spanish for "The Meadows"), often known simply as Vegas, is the 25th-most populous city in the United States, the most populous city in the state of Nevada, and the county seat of Clark County. The city anchors the Las Vegas ...
, and the
IBC IBC is an initialism that can stand for:
Broadcasting
*Intercontinental Broadcasting Corporation, Channel 13, Philippines
* International Beacon Project, Worldwide network of radio propagation beacons
*International Broadcast Centre
*International ...
trade shows 2006 and 2008,
Amsterdam
Amsterdam ( , , , lit. ''The Dam on the River Amstel'') is the Capital of the Netherlands, capital and Municipalities of the Netherlands, most populous city of the Netherlands, with The Hague being the seat of government. It has a population ...
,
Netherlands
)
, anthem = ( en, "William of Nassau")
, image_map =
, map_caption =
, subdivision_type = Sovereign state
, subdivision_name = Kingdom of the Netherlands
, established_title = Before independence
, established_date = Spanish Netherl ...
.
See also
*
3D audio effect
*
Binaural recording
Binaural recording is a method of recording sound that uses two microphones, arranged with the intent to create a 3-D stereo sound sensation for the listener of actually being in the room with the performers or instruments. This effect is ...
*
Dolby Surround
*
Duophonic
Duophonic sound was a trade name for a type of audio signal processing used by Capitol Records on certain releases and re-releases of mono recordings issued during the 1960s and 1970s. In this process monaural recordings were reprocessed into a ...
*
Four-channel Compact Disc Digital Audio
Compact Disc recordings contain two channels of 44.1-kHz 16-bit linear Pulse-code modulation, PCM audio. However, creators of the CD originally contemplated a four-channel, or quadraphonic, mode as well.
The proprietary Red Book (CD standard), Red ...
*
Holophonics
Holophonics is a binaural recording system created by Hugo Zuccarelli that is based on the claim that the human auditory system acts as an interferometer. It relies on phase variance, just like stereophonic sound. The sound characteristics of h ...
*
MPEG Surround
*
Precedence effect
The precedence effect or law of the first wavefront is a binaural psychoacoustical effect. When a sound is followed by another sound separated by a sufficiently short time delay (below the listener's echo threshold), listeners perceive a single ...
*
Soundfield microphone
The Soundfield microphone is an audio microphone composed of four closely spaced subcardioid or cardioid (unidirectional) microphone capsules arranged in a tetrahedron. It was invented by Michael Gerzon and Peter Craven, and is a part of, but not ...
*
Virtual surround
Virtual surround is an audio system that 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 int ...
Notes
References
External links
*
{{Authority control
Consumer electronics
Film sound production
Home video
Virtual reality