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. This is usually achieved by using two or more independent
audioSound 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...
channels through a configuration of two or more
loudspeakerA loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...
s in such a way as to create the impression of sound heard from various directions, as in natural hearing. Thus the term "stereophonic" applies to so-called "
quadraphonicQuadraphonic 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...
" and "
surround-soundSurround sound encompasses a range of techniques such as for enriching the sound reproduction 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...
" systems as well as the more common 2-channel, 2-speaker systems. It is often contrasted with
monophonicMonaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...
, or "mono" sound, where audio is in the form of one channel, often centered in the sound field (analogous to a
visual fieldThe term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments", while 'field of view' "refers to the physical...
).
Stereo sound is now common in entertainment systems such as broadcast radio and TV, recorded music and the cinema.
The word
stereophonic derives from the
GreekGreek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
"στερεός" (
stereos), "firm, solid" + "φωνή" (
phōnē), "sound, tone, voice" and it was coined in 1927 by
Western ElectricWestern Electric Company was an American electrical engineering company, the manufacturing arm of AT&T from 1881 to 1995. It was the scene of a number of technological innovations and also some seminal developments in industrial management...
, by analogy with the word "stereoscopic".
Description
Stereo sound systems can be divided into two forms: The first is "true" or "natural" stereo in which a live sound is captured, with any natural reverberation or ambience present, by an array of microphones. The signal is then reproduced over multiple loudspeakers to recreate, as closely as possible, the live sound.
Secondly "artificial" or "pan-pot" stereo, in which a single-channel (mono) sound is reproduced over multiple loudspeakers. By varying the relative amplitude of the signal sent to each speaker an artificial direction (relative to the listener) can be suggested. The control which is used to vary this relative amplitude of the signal is known as a "pan-pot" (panoramic potentiometer). By combining multiple "pan-potted" mono signals together, a complete, yet entirely artificial, sound field can be created.
In the 21st century "true" stereo is mainly confined to recordings or broadcast of live, acoustic music, particularly classical music. Almost all pop records and movie soundtracks are of the "artificial" variety.
In technical usage,
true stereo means sound recording and sound reproduction that uses
stereographic projectionThe stereographic projection, in geometry, is a particular mapping that projects a sphere onto a plane. The projection is defined on the entire sphere, except at one point — the projection point. Where it is defined, the mapping is smooth and bijective. It is conformal, meaning that it...
to encode the relative positions of objects and events recorded.
During two-channel stereo recording, two microphones are placed in strategically chosen locations relative to the sound source, with both recording simultaneously. The two recorded channels will be similar, but each will have distinct time-of-arrival and sound-pressure-level information. During playback, the listener's brain uses those subtle differences in timing and sound level to
triangulateIn trigonometry and geometry, triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline, rather than measuring distances to the point directly...
the positions of the recorded objects. Stereo recordings often cannot be played on monaural systems without a significant loss of
fidelityHigh fidelity—or hi-fi—reproduction is a term used by home stereo listeners and home audio enthusiasts to refer to high-quality reproduction of sound or images, to distinguish it from the poorer quality sound produced by inexpensive audio equipment...
. Since each microphone records each
wavefrontIn physics, a wavefront is the locus of points having the same phase. Since infrared, optical, x-ray and gamma-ray frequencies are so high, the temporal component of electromagnetic waves is usually ignored at these wavelengths, and it is only the phase of the spatial oscillation that is described...
at a slightly different time, the wavefronts are out of
phasePhase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.-Formula:The phase of an oscillation or wave refers to a sinusoidal function such as the following:...
; as a result, constructive and destructive interference can occur if both tracks are played back on the same speaker. This phenomenon is known as phase cancellation.
1881
Clément AderClément Ader was a French inventor and engineer born in Muret, Haute Garonne, and is remembered primarily for his pioneering work in aviation.- The inventor :...
demonstrated the first two-channel audio system in Paris in 1881, with a series of telephone transmitters connected from the stage of the
Paris OperaThe Palais Garnier, , is an elegant 1,979-seat opera house, which was built from 1861 to 1875 for the Paris Opera. It was originally called the Salle des Capucines because of its location on the Boulevard des Capucines in the 9th arrondissement of Paris, but soon became known as the Palais Garnier...
to a suite of rooms at the Paris Electrical Exhibition, where listeners could hear a live transmission of performances through receivers for each ear.
Scientific AmericanScientific American is a popular science magazine. It is notable for its long history of presenting science monthly to an educated but not necessarily scientific public, through its careful attention to the clarity of its text as well as the quality of its specially commissioned color graphics...
reported,
- "Every one who has been fortunate enough to hear the telephones at the Palais de l'Industrie has remarked that, in listening with both ears at the two telephones, the sound takes a special character of relief and localization which a single receiver cannot produce… This phenomenon is very curious, it approximates to the theory of binauricular audition, and has never been applied, we believe, before to produce this remarkable illusion to which may almost be given the name of auditive perspective."
This two-channel telephonic process was commercialized in France from 1890 to 1932 as the
ThéâtrophoneThéâtrophone was a telephonic distribution system that allowed the subscribers to listen to opera and theatre performances over the telephone lines. The théâtrophone evolved from a Clément Ader invention, which was first demonstrated in 1881, in Paris...
, and in England from 1895 to 1925 as the
ElectrophoneThe name Electrophone was used for a telephone-distributed audio system which operated in the United Kingdom between 1895 and 1926, relaying live theatre and music hall shows and, on Sundays, live sermons from churches via special headsets connected to conventional phone lines...
. Both were services available by coin-operated receivers at hotels and cafés, or by subscription to private homes.
1930s
In the 1930s,
Alan BlumleinAlan Dower Blumlein was a British electronics engineer, notable for his many inventions in telecommunications, sound recording, stereo, television and radar...
at
EMIThe EMI Group, also known as EMI Music or simply EMI, is a multinational music company headquartered in London, United Kingdom. It is the fourth-largest business group and family of record labels in the recording industry and one of the "big four" record companies. EMI Group also has a major...
patented stereo records, stereo films, and also surround sound. The two stereophonic recording methods, using two channels and coincident microphone techniques (X-Y with bidirectional transducers/Blumlein setup + M/S stereophony), were developed by Blumlein at
EMIThe EMI Group, also known as EMI Music or simply EMI, is a multinational music company headquartered in London, United Kingdom. It is the fourth-largest business group and family of record labels in the recording industry and one of the "big four" record companies. EMI Group also has a major...
in 1931 and patented in 1933. A stereo disc, using the two walls of the groove at right angles in order to carry the two channels, was cut at EMI in 1933, twenty-five years before that method became the standard for stereo phonograph discs.
Harvey FletcherHarvey Fletcher was an American physicist. Known as the "father of stereophonic sound" he is credited with the invention of the audiometer and hearing aid...
of Bell Laboratories investigated techniques for stereophonic recording and reproduction. One of the techniques investigated was the "wall of sound", which used an enormous array of microphones hung in a line across the front of an orchestra. Up to 80 microphones were used, and each fed a corresponding loudspeaker, placed in an identical position, in a separate listening room. Several stereophonic test recordings, using two microphones connected to two styli cutting two separate grooves on the same wax disc, were made with
Leopold StokowskiLeopold Anthony Stokowski was a British-born, naturalised American orchestral conductor, well known for his free-hand performing style that spurned the traditional baton and for obtaining a characteristically sumptuous sound from many of the great orchestras he conducted.In America, Stokowski...
and the
Philadelphia OrchestraThe Philadelphia Orchestra is a symphony orchestra based in Philadelphia, Pennsylvania, in the United States. One of the "Big Five" American orchestras, it was founded in 1900...
at Philadelphia's
Academy of MusicThe Academy of Music, also known as American Academy of Music, is a concert hall and opera house located at Broad and Locust Streets in Philadelphia, Pennsylvania. It was built in 1857 and is the oldest opera house in the United States that is still used for its original purpose...
in March 1932. The first (made on March 12, 1932), of
Scriabin'sAlexander Nikolayevich Scriabin was a Russian composer and pianist who initially developed a lyrical and idiosyncratic tonal language inspired by the music of Frédéric Chopin. Quite independent of the innovations of Arnold Schoenberg, Scriabin developed an increasingly atonal musical system,...
Prometheus: Poem of FirePrometheus: The Poem of Fire, Op. 60 , is a symphonic work by the Russian composer Alexander Scriabin for piano, orchestra, optional choir, and clavier à lumières or "Chromola" . However, the clavier à lumières is rarely featured in the performance of the piece, including performances during...
, is the earliest known surviving intentional stereo recording.
Accidental stereophonic recordings from these years also exist. On some occasions, RCA Victor used two microphones, two amplifiers and two recording lathes to make two simultaneous but completely separate recordings of a performance. Although this may have been done to compare the results obtained with different microphones or other technical variations, the reasons for this procedure have not been definitely established. Normally, only one of the resulting pair of recordings was released, but the other-channel recording was sometimes used for a foreign issue or survived in the form of a test pressing. When such pairs of recordings have been located and matched up, authentic stereophonic sound has been recovered, its character and degree of spatial accuracy dependent on the fortuitous placement of the two microphones and the accurate synchronization of the two recordings. Recovered stereophonic versions of two recordings made in February 1932 by Duke Ellington and His Orchestra have been issued on LP and CD under the title
Stereo Reflections in Ellington and are also included in the 22-CD set
The Duke Ellington Centennial Edition.
Bell Laboratories gave a demonstration of three-channel stereophonic sound on April 27, 1933, with a live transmission of the
Philadelphia OrchestraThe Philadelphia Orchestra is a symphony orchestra based in Philadelphia, Pennsylvania, in the United States. One of the "Big Five" American orchestras, it was founded in 1900...
from Philadelphia to Constitution Hall in Washington, D.C.
Leopold StokowskiLeopold Anthony Stokowski was a British-born, naturalised American orchestral conductor, well known for his free-hand performing style that spurned the traditional baton and for obtaining a characteristically sumptuous sound from many of the great orchestras he conducted.In America, Stokowski...
, normally the orchestra's conductor, was present in Constitution Hall to control the sound mix. Bell Labs also demonstrated binaural sound, using a dummy with microphones instead of ears, at the
Chicago World's FairA Century of Progress International Exposition was the name of a World's Fair held in Chicago from 1933 to 1934 to celebrate the city's centennial. The theme of the fair was technological innovation...
in 1933. The two signals were sent out over separate
AMAmplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
station bands.
The 1940 Carnegie Hall demonstration
The
Carnegie HallCarnegie Hall is a concert venue in Midtown Manhattan in New York City, United States, located at 881 Seventh Avenue, occupying the east stretch of Seventh Avenue between West 56th Street and West 57th Street, two blocks south of Central Park....
demonstration by Bell Laboratories on April 9 and 10, 1940, used three huge speaker systems. Synchronization was achieved by making the recordings in the form of three motion picture soundtracks recorded on a single piece of film. Because of dynamic range limitations, volume compression was used, with a fourth track being used to regulate volume expansion. The volume compression and expansion were not fully automatic, but were designed to allow manual studio "enhancement"; i.e., the artistic adjustment of overall volume and the relative volume of each track. The recordings had been made by the
Philadelphia OrchestraThe Philadelphia Orchestra is a symphony orchestra based in Philadelphia, Pennsylvania, in the United States. One of the "Big Five" American orchestras, it was founded in 1900...
, conducted by
Leopold StokowskiLeopold Anthony Stokowski was a British-born, naturalised American orchestral conductor, well known for his free-hand performing style that spurned the traditional baton and for obtaining a characteristically sumptuous sound from many of the great orchestras he conducted.In America, Stokowski...
, who was always interested in sound reproduction technology. Stokowski personally participated in the "enhancement" of the sound.
The speakers produced sound levels of up to 100 decibels, and the demonstration held the audience "spellbound, and at times not a little terrified", according to one report.
Sergei RachmaninoffSergei Vasilievich Rachmaninoff was a Russian composer, pianist, and conductor. Rachmaninoff is widely considered one of the finest pianists of his day and, as a composer, one of the last great representatives of Romanticism in Russian classical music...
, who was present at the demonstration, commented that it was "marvellous" but "somehow unmusical because of the loudness." "Take that
Pictures at an ExhibitionPictures at an Exhibition is a suite in ten movements composed for piano by Russian composer Modest Mussorgsky in 1874.The suite is Mussorgsky's most famous piano composition, and has become a showpiece for virtuoso pianists...
", he said. "I didn't know what it was until they got well into the piece. Too much 'enhancing', too much Stokowski."
Motion picture era
In 1937, Bell Laboratories in New York City gave a demonstration of two-channel stereophonic motion pictures, developed by Bell Labs and Electrical Research Products, Inc. Conductor
Leopold StokowskiLeopold Anthony Stokowski was a British-born, naturalised American orchestral conductor, well known for his free-hand performing style that spurned the traditional baton and for obtaining a characteristically sumptuous sound from many of the great orchestras he conducted.In America, Stokowski...
recorded onto a nine-track sound system at the
Academy of MusicThe Academy of Music, also known as American Academy of Music, is a concert hall and opera house located at Broad and Locust Streets in Philadelphia, Pennsylvania. It was built in 1857 and is the oldest opera house in the United States that is still used for its original purpose...
in Philadelphia, during the making of the movie
One Hundred Men and a GirlOne Hundred Men and a Girl is a 1937 musical comedy film, written by Charles Kenyon, Bruce Manning and James Mulhauser from a story by Hanns Kräly and directed by Henry Koster...
for
Universal Pictures-1920:* White Youth* The Flaming Disc* Am I Dreaming?* The Dragon's Net* The Adorable Savage* Putting It Over* The Line Runners-1921:* The Fire Eater* A Battle of Wits* Dream Girl* The Millionaire...
in 1937. The tracks were mixed down to one for the final soundtrack. In 1938,
Metro-Goldwyn-MayerMetro-Goldwyn-Mayer Inc. is an American media company, involved primarily in the production and distribution of films and television programs. MGM was founded in 1924 when the entertainment entrepreneur Marcus Loew gained control of Metro Pictures, Goldwyn Pictures Corporation and Louis B. Mayer...
started using three tracks instead of one to record movie soundtracks, and very quickly upgraded to four tracks. One track was used for dialogue, two for music, and one for sound effects. The purpose for this form of multitrack recording was to make mixing down to a single optical track easier and was not intended to be a recording for stereophonic purposes. The very first binaural recording MGM made (although released in mono) was "It Never Rains But What It Pours" by
Judy GarlandJudy Garland was an American actress and singer. Through a career that spanned 45 of her 47 years and for her renowned contralto voice, she attained international stardom as an actress in musical and dramatic roles, as a recording artist and on the concert stage...
, recorded on June 21, 1938, for the movie
Love Finds Andy Hardy.
Walt DisneyWalter 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...
began experimenting with multi-channel sound in the early 1930s. The first commercial motion picture to be exhibited with stereophonic sound was Walt Disney's
FantasiaFantasia 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...
, released in November 1940, for which a specialized sound process (
FantasoundFantasound 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...
) was developed. Fantasound used a separate film containing four optical sound tracks. Three of the tracks were used to carry left, center and right audio, while the fourth track carried three tones which individually controlled the volume level of the other three. The film was not a financial success, however, and after two months of road-show exhibition in selected cities, its soundtrack was remixed into mono sound for general release. In the early 1940s, composer-conductor
Alfred NewmanAlfred Newman was an American composer, arranger, and conductor of music for films.In a career which spanned over forty years, Newman composed music for over two hundred films. He was one of the most respected film score composers of his time, and is today regarded as one of the greatest...
directed the construction of a sound stage equipped for multichannel recording for 20th Century Fox studios. Several soundtracks from this era still exist in their multichannel elements, some of which have been released on DVD, including
How Green Was My ValleyHow Green Was My Valley is a 1941 drama film directed by John Ford. The film, based on the 1939 Richard Llewellyn novel, was produced by Darryl F. Zanuck and written by Philip Dunne. The film stars Walter Pidgeon, Maureen O'Hara, Anna Lee, Donald Crisp, and Roddy McDowall...
,
Anna and the King of Siam,
Sun Valley SerenadeSun Valley Serenade is a 1941 musical film starring Sonja Henie, John Payne, Glenn Miller, Milton Berle, and Lynn Bari. It features The Glenn Miller Orchestra as well as dancing by The Nicholas Brothers and Dorothy Dandridge, performing "Chattanooga Choo Choo", which was nominated for an Academy...
, and
The Day the Earth Stood Still.
The advent of magnetic tape recording made high fidelity synchronized multichannel recording technically straightforward, though costly. By the early 1950s, all of the major studios were recording on 35mm magnetic film for mixing purposes. Motion picture theatres, however, are where the real introduction of stereophonic sound to the public occurred. Stereo sound was proven viable with the release of
This is CineramaThis is Cinerama is a 1952 full-length film designed to introduce the then-new widescreen process Cinerama, which broadens the aspect ratio so the viewer's peripheral vision is involved...
on September 30, 1952.
CineramaCinerama is the trademarked name for a widescreen process which works by simultaneously projecting images from three synchronized 35 mm projectors onto a huge, deeply-curved screen, subtending 146° of arc. It is also the trademarked name for the corporation which was formed to market it...
was a spectacular widescreen process in some ways comparable to today's
IMAXIMAX 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...
. Cinerama's audio soundtrack utilized seven discrete magnetic sound tracks: five behind the screen, plus two surround channels. The system was developed by
Hazard E. ReevesHazard E. Reeves was a pioneer in sound and sound electronics, and introduced magnetic stereophonic sound to motion pictures...
, a pioneer in magnetic recording technology. By all accounts (including accounts by those who have experienced the process in rare recent showings), the sound was as spectacular as the picture, even excellent, by modern standards.
In April 1953, while
This is Cinerama was still playing only in New York City, most moviegoing audiences heard stereophonic sound for the first time with the Warner Bros.
3-D filmA 3-D film or S3D film is a motion picture that enhances the illusion of depth perception...
production of
House of WaxHouse of Wax is a 1953 American horror film starring Vincent Price. It is a remake of Warners' Mystery of the Wax Museum without the comic relief featured in the earlier film, and was directed by André de Toth...
, starring
Vincent PriceVincent Leonard Price, Jr. was an American actor, well known for his distinctive voice and serio-comic attitude in a series of horror films made in the latter part of his career.-Early life and career:Price was born in St...
. The sound system, WarnerPhonic, was a combination of a 35 mm magnetic full-coat that contained Left-Center-Right, interlocked with the two dual-strip
PolaroidPolaroid Corporation is an American-based international consumer electronics and eyewear company, originally founded in 1937 by Edwin H. Land. It is most famous for its instant film cameras, which reached the market in 1948, and continued to be the company's flagship product line until the February...
system projectors, one of which carried an optical surround track and one that carried a mono backup track, should anything go wrong. Only two other films carried WarnerPhonic sound: the 3-D production of
The Charge at Feather River, and
Island in the Sky. The magnetic tracks to these films are considered lost. A large percentage of 3-D films carried variations on three-track magnetic sound. Among them were
It Came from Outer SpaceIt Came from Outer Space is a 1953 science fiction 3-D film directed by Jack Arnold, and starring Richard Carlson, Barbara Rush, and Charles Drake. It was Universal's first film to be filmed in 3-D.- Plot :...
;
I, the Jury;
The Stranger Wore a Gun;
Inferno;
Kiss Me, KateKiss Me Kate is the 1953 MGM film adaptation of the Broadway musical of the same name.Inspired by The Taming of the Shrew, it tells the tale of musical theater actors, Fred Graham and Lilli Vanessi, who were once married and are now performing opposite each other in the roles of Petruchio and...
; and many others.
Inspired by
CineramaCinerama is the trademarked name for a widescreen process which works by simultaneously projecting images from three synchronized 35 mm projectors onto a huge, deeply-curved screen, subtending 146° of arc. It is also the trademarked name for the corporation which was formed to market it...
, the movie industry moved quickly to create simpler and cheaper widescreen systems, such as Twentieth Century-Fox Film Corporation's
CinemaScopeCinemaScope was an anamorphic lens series used for shooting wide screen movies from 1953 to 1967. Its creation in 1953, by the president of 20th Century-Fox, marked the beginning of the modern anamorphic format in both principal photography and movie projection.The anamorphic lenses theoretically...
, which used up to four magnetic sound tracks. Because of the standard 35 mm-size film, CinemaScope and its stereophonic sound was capable of being retrofitted into existing theaters.
CinemaScope 55CinemaScope 55 was a large-format version of CinemaScope introduced by Twentieth Century Fox in 1955, which used a film width of 55.625 mm ....
was created by the same company in order to use a larger form of the system (55 mm instead of 35 mm), and was supposed to have had 6-track stereo. However, because the film needed a new, specially designed projector, the system proved impractical, and the two films made in it,
CarouselCarousel is a 1956 film adaptation of the 1945 Rodgers and Hammerstein musical of the same name which, in turn, was based on Ferenc Molnár's non-musical play Liliom. The 1956 Carousel film stars Gordon MacRae and Shirley Jones, and was directed by Henry King...
and
The King and IThe King and I is a 1956 musical film made by 20th Century Fox, directed by Walter Lang and produced by Charles Brackett and Darryl F. Zanuck. The screenplay by Ernest Lehman is based on the Richard Rodgers and Oscar Hammerstein II musical The King and I, based in turn on the book Anna and the King...
, were released in 35 mm CinemaScope reduction prints. To compensate, the premiere engagement of
Carousel used a six-track magnetic full-coat in an interlock, and a 1961 re-release of
The King and I, with the film "blown up" to 70 mm, also used a six-track stereo soundtrack. However, 50 complete sets of combination 55/35 mm projectors and "penthouse" reproducers were eventually completed and delivered by Century and Ampex, respectively. 55 mm release print sounding equipment was delivered by Western Electric and samples of sounded 55 mm prints are on file in the Sponable Collection at Columbia University. The subsequently abandoned 55/35 mm Century projector eventually became the Century JJ 70/35 mm projector. After this disappointing experience with a proprietary "wide gauge" system, Fox purchased the Todd-AO system and re-engineered it into a more modern 24 fps system with brand-new 65 mm self-blimped production cameras (Mitchell BFC ... "Blimped Fox Camera") and brand-new 65 mm MOS cameras (Mitchell FC ... "Fox Camera") and brand-new Super Baltar lenses in a wide variety of focal lengths, first employed on
South PacificSouth Pacific is a 1958 musical romance film adaptation of the Rodgers and Hammerstein musical South Pacific, and based on James A. Michener's Tales of the South Pacific...
. Essentially, Todd-AO became Fox's premier origination and presentation system, replacing CinemaScope 55, although the Todd-AO system was also available to others. Current DVDs of the two CinemaScope 55 feature titles were transferred from the original 55mm negatives.
However, beginning in 1957, films recorded in stereo (except for those shown in Cinerama) carried an alternate mono track for theatres not ready or willing to re-equip for stereo. From then until about 1975, when
Dolby StereoDolby Stereo, is the trade mark that Dolby Laboratories used for the various analogue stereo cinema sound formats that they produced.Two basic systems used this name. The first was the 'Dolby SVA' system used with optical soundtracks on 35mm film...
was used for the first time in films, most motion pictures—even some from which stereophonic soundtrack albums were made, such as Zeffirelli's
Romeo and JulietRomeo and Juliet is a 1968 British-Italian cinematic adaptation of the William Shakespeare play of the same name.The film was directed and co-written by Franco Zeffirelli, and stars Leonard Whiting and Olivia Hussey. It won Academy Awards for Best Cinematography and Best Costume Design; it was also...
—were still released in monaural sound, stereo being reserved almost exclusively for expensive musicals such as
West Side StoryWest Side Story is a 1961 musical film directed by Robert Wise and Jerome Robbins. The film is an adaptation of the 1957 Broadway musical of the same name, which in turn was adapted from William Shakespeare's play Romeo and Juliet. It stars Natalie Wood, Richard Beymer, Russ Tamblyn, Rita Moreno,...
,
My Fair LadyMy Fair Lady is a 1964 musical film adaptation of the Lerner and Loewe stage musical, of the same name, based on the 1938 film adaptation of the original stage play Pygmalion by George Bernard Shaw. The ballroom scene and the ending were taken from the previous film adaptation , rather than from...
, or
CamelotCamelot is a 1967 film adaptation of the musical of the same name. Richard Harris stars as Arthur, Vanessa Redgrave as Guinevere, and Franco Nero as Lancelot. The film was directed by Joshua Logan.-Plot:...
; epics such as
Ben-HurBen-Hur is a 1959 American epic film directed by William Wyler and starring Charlton Heston in the title role, the third film adaptation of Lew Wallace's 1880 novel Ben-Hur: A Tale of the Christ. The screenplay was written by Karl Tunberg, Gore Vidal, and Christopher Fry. The score was composed by...
or
CleopatraCleopatra is a 1963 British-American-Swiss epic drama film directed by Joseph L. Mankiewicz. The screenplay was adapted by Sidney Buchman, Ben Hecht, Ranald MacDougall, and Mankiewicz from a book by Carlo Maria Franzero. The film starred Elizabeth Taylor, Richard Burton, Rex Harrison, Roddy...
; or dramas with a strong reliance on sound effects or music, such as
The GraduateThe Graduate is a 1967 American comedy-drama motion picture directed by Mike Nichols. It is based on the 1963 novel The Graduate by Charles Webb, who wrote it shortly after graduating from Williams College. The screenplay was by Buck Henry, who makes a cameo appearance as a hotel clerk, and Calder...
, with its
Simon and GarfunkelSimon & Garfunkel are an American duo consisting of singer-songwriter Paul Simon and singer Art Garfunkel. They formed the group Tom & Jerry in 1957 and had their first success with the minor hit "Hey, Schoolgirl". As Simon & Garfunkel, the duo rose to fame in 1965, largely on the strength of the...
score. Today, virtually all films are released in stereophonic sound as 1977's Westrex Stereo Variable-Area system is no more expensive to manufacture than mono (it employs the same recorder, the Western Electric/Westrex/Nuoptix RA-1231), and with Dolby Labs' matrixing technology (actually licensed from Sansui) this S V-A system can produce the Left, Center, Right and Surround sound of 1953's CinemaScope system using a standard width optical track. This important development finally brought stereo sound to so-called Flat Wide-Screen (preferentially 1.85:1, but sometimes 1.75:1 or 1.66:1) theatrical productions.
Producers often took advantage of the six magnetic soundtracks in 70mm film, and productions shot in 65 mm (or 35 mm and then blown up to 70 mm) would be mixed for stereo, while the 35mm reduction prints would be remixed for mono.
Some films shot in 35mm, such as
Camelot, featured four-track stereophonic sound and were then "blown-up" to 70mm so that they could be shown on a giant screen with six-track stereophonic sound, but many were pseudo six-track as the "Columbia Spread" was often used to synthesize Left Center and Right Center from a combination of Left and Center and Right and Center, respectively, or, for effects, the effect could be "panned" anywhere across the five stage speakers using a one-in/five-out pan pot.
Consumer media
From 1940 to 1970, the progress of stereophonic sound was paced by the technical difficulties of recording and reproducing two or more channels in synchronization and by the economic and marketing issues of introducing new audio media and equipment. A stereo system cost roughly twice as much as a monophonic system, since a stereo system had to be assembled by buying two preamplifiers, two amplifiers, and two speaker systems. It was not clear whether consumers would think the sound was so much better as to be worth twice the price.
In 1952, Emory Cook (1913–2002), who already had become famous by designing new feedback disk-cutter heads to improve sound from tape to vinyl, developed a "binaural" record. This record consisted of two separate channels, cut into two separate grooves running next to each other. Each groove needed a needle, and each needle was connected to a separate amplifier and speaker. This setup was intended to give a demonstration at a New York audio fair of Cook's cutter heads rather than to sell the record; but soon afterward, the demand for such recordings and the equipment to play it grew, and Cook Records began to produce such records commercially. Cook recorded a vast array of sounds, ranging from railroad sounds to thunderstorms.
[The term "binaural" that Cook used should not be confused with the modern use of the word, where "binaural" is an inner-ear recording using small microphones placed in the ear. Cook used conventional microphones, but used the same word, "binaural", that Alan Blumlein]Alan Dower Blumlein was a British electronics engineer, notable for his many inventions in telecommunications, sound recording, stereo, television and radar...
had used for his experimental stereo records almost 20 years earlier. By 1953, Cook had a catalog of about 25 stereo records for sale to
audiophileAn audiophile is a person who enjoys listening to recorded music, usually in a home. Some audiophiles are more interested in collecting and listening to music, while others are more interested in collecting and listening to audio components, whose "sound quality" they consider as important as the...
s.
Stereo magnetic tape recording, using two recording and playback heads on standard 1/4-inch tape, was demonstrated in 1952. In 1953,
Remington RecordsRemington Records was a low budget record label. It existed from 1950 until 1957 and specialized in classical music. Unfortunately, the discs suffered from considerable surface noise.-History:...
began taping some of its sessions in stereo, including performances by
Thor JohnsonThor Martin Johnson was an American conductor. He was born in Wisconsin Rapids, Wisconsin. He studied at the University of North Carolina at Chapel Hill, where he was president of the Alpha Rho chapter of Phi Mu Alpha Sinfonia Fraternity. He was the first recipient of the fraternity's national...
and the
Cincinnati Symphony OrchestraAs the fifth oldest orchestra in the United States, the Cincinnati Symphony Orchestra has a legacy of fine music making as reflected in its performances in historic Music Hall, recordings, and international tours...
. Later that year, RCA Victor conducted some experimental stereo tapings with
Leopold StokowskiLeopold Anthony Stokowski was a British-born, naturalised American orchestral conductor, well known for his free-hand performing style that spurned the traditional baton and for obtaining a characteristically sumptuous sound from many of the great orchestras he conducted.In America, Stokowski...
and a group of New York musicians. In February 1954, RCA taped the
Boston Symphony OrchestraThe Boston Symphony Orchestra is an orchestra based in Boston, Massachusetts. It is one of the five American orchestras commonly referred to as the "Big Five". Founded in 1881, the BSO plays most of its concerts at Boston's Symphony Hall and in the summer performs at the Tanglewood Music Center...
, conducted by
Charles MünchCharles Munch was an Alsatian symphonic conductor and violinist. Noted for his mastery of the French orchestral repertoire, he is best known as music director of the Boston Symphony Orchestra.-Biography:...
, in a performance of Berlioz'
Damnation of Faust, which led to regular stereo tapings by the company. Shortly afterwards, conductor
Arturo ToscaniniArturo Toscanini was an Italian conductor. One of the most acclaimed musicians of the late 19th and 20th century, he was renowned for his intensity, his perfectionism, his ear for orchestral detail and sonority, and his photographic memory...
's last two public concerts were recorded on stereophonic magnetic tape. They were, however, not released in stereo until 1987 and 2007, respectively. In the UK,
Decca RecordsDecca Records began as a British record label established in 1929 by Edward Lewis. Its U.S. label was established in late 1934; however, owing to World War II, the link with the British company was broken for several decades....
began taping in stereo in mid-1954. In 1954, companies such as Concertapes and RCA Victor began releasing stereophonic recordings on two-track prerecorded reel-to-reel magnetic tape, priced at twice the cost of monaural recordings. Serious audiophiles, the sort of people who would later be called "early adopters", bought them, and stereophonic sound came to at least some living rooms. Stereo recording became widespread in the music business by the 3rd quarter of 1957.
The small record label
Audio Fidelity RecordsAudio Fidelity Records, was a record company out of New York City, most active during the 1950s and 1960s. They are best known for having produced the first mass-produced American stereophonic long-playing record in November 1957 .-Background:Sidney Frey , founder and president of...
released the
first mass-produced stereophonic disc in November 1957. Sidney Frey, founder and president, had Westrex (owners of one of the two rival stereo disk-cutting systems) cut a disk for release before any of the major record labels. Side 1 was the Dukes of Dixieland, and Side 2 was railroad sound effects. This demonstration disc was introduced to the public on December 13, 1957 at the Times Auditorium in New York City 500 copies of this initial demonstration record were pressed. Three days later, Frey advertised in the trade magazine
Billboard that he would send a free copy to anyone in the industry who wrote to him on company letterhead.
That move generated a great deal of publicity. Dealers in stereo phonograph equipment had no choice but to demonstrate on Audio Fidelity Records. After the release of the demonstration disc, the other spur to the popularity of stereo discs was the reduction in price of a stereo
magnetic cartridgeA magnetic cartridge is a transducer used for the playback of gramophone records on a turntable or phonograph. It converts mechanical vibrational energy from a stylus riding in a spiral record groove into an electrical signal that is subsequently amplified and then converted back to sound by a...
, for playing the disks, from $250 to $29.95 in June 1958. The
first four mass-produced stereophonic discs available to the buying public were released in March, 1958—
Johnny Puleo and his Harmonica Gang Volume 1 (AFSD 5830),
Railroad – Sounds of a Vanishing Era (AFSD 5843),
Lionel – Lionel Hampton and his Orchestra (AFSD 5849) and
Marching Along with the Dukes of Dixieland Volume 3 (AFSD 5851). By the end of March, the company had four more stereo LPs available.
By 1968, the major record labels stopped making monaural discs.
Early broadcasting
Radio: In December 1925, the
BBCThe British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
's experimental transmitting station, 5XX, in Daventry, Northamptonshire, made radio's first stereo broadcast—a concert from
ManchesterManchester is a city and metropolitan borough in Greater Manchester, England. According to the Office for National Statistics, the 2010 mid-year population estimate for Manchester was 498,800. Manchester lies within one of the UK's largest metropolitan areas, the metropolitan county of Greater...
, conducted by
Sir Hamilton HartySir Hamilton Harty was an Irish and British composer, conductor, pianist and organist. In his capacity as a conductor, he was particularly noted as an interpreter of the music of Berlioz and he was much respected as a piano accompanist of exceptional prowess...
—with 5XX broadcasting the right channel nationally by long wave and local BBC stations broadcasting the left channel by medium wave. The BBC repeated the experiment in 1926, using 2LO in London and 5XX at Daventry. Following experimental FM stereo transmissions in the London area in 1958 and regular Saturday morning demonstration transmissions using TV sound and medium wave (AM) radio to provide the two channels, the first regular BBC transmissions using an FM stereo signal began on the BBC's
Third ProgrammeThe BBC Third Programme was a national radio network broadcast by the BBC. The network first went on air on 29 September 1946 and became one of the leading cultural and intellectual forces in Britain, playing a crucial role in disseminating the arts...
network on August 28, 1962.
Chicago
AMAM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a radio signal and is still widely used today. Commercial and public AM broadcasting is carried out in the medium wave band world wide, and on long wave and short wave...
radio station
WGNWGN is a radio station in Chicago, Illinois, USA. It is the only radio station owned by the Tribune Company, which also owns the flagship television station WGN-TV, the Chicago Tribune newspaper and Chicago magazine locally. WGN's transmitter is located in Elk Grove Village, Illinois...
(and its sister
FMFM broadcasting is a broadcasting technology pioneered by Edwin Howard Armstrong which uses frequency modulation to provide high-fidelity sound over broadcast radio. The term "FM band" describes the "frequency band in which FM is used for broadcasting"...
station, WGNB) collaborated on an hourlong stereophonic demonstration broadcast on May 22, 1952, with one audio channel broadcast by the AM station and the other audio channel by the FM station. New York City's WQXR initiated its first stereophonic broadcasts in October 1952, and by 1954, was broadcasting all of its live musical programs in stereophonic sound, using its AM and FM stations for the two audio channels.
Rensselaer Polytechnic InstituteStephen Van Rensselaer established the Rensselaer School on November 5, 1824 with a letter to the Rev. Dr. Samuel Blatchford, in which van Rensselaer asked Blatchford to serve as the first president. Within the letter he set down several orders of business. He appointed Amos Eaton as the school's...
began a weekly series of live stereophonic broadcasts in November 1952 by using two campus-based AM stations, although the listening area did not extend beyond the campus.
Tests of six competing FM-only systems were conducted on KDKA-FM in Pittsburgh, Pennsylvania during July and August 1960. The
Federal Communications CommissionThe Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
announced stereophonic
FMFM broadcasting is a broadcasting technology pioneered by Edwin Howard Armstrong which uses frequency modulation to provide high-fidelity sound over broadcast radio. The term "FM band" describes the "frequency band in which FM is used for broadcasting"...
technical standards in April 1961, with licensed regular stereophonic FM radio broadcasting set to begin in the United States on June 1, 1961.
WEFMWUSN is an FM radio station in Chicago, Illinois, The station broadcasts on 99.5 MHz and is a country radio station owned by CBS Radio. The station focuses on country music from the '90s, along with current product and some classic country from the '70s and '80s.-99.5 WEFM/99-"We" FM:Until 1978,...
(in the Chicago area) and WGFM (in
Schenectady, New YorkSchenectady is a city in Schenectady County, New York, United States, of which it is the county seat. As of the 2010 census, the city had a population of 66,135...
) were reported as the first stereo stations.
Television: A December 11, 1952 closed-circuit television performance of
CarmenCarmen is a French opéra comique by Georges Bizet. The libretto is by Henri Meilhac and Ludovic Halévy, based on the novella of the same title by Prosper Mérimée, first published in 1845, itself possibly influenced by the narrative poem The Gypsies by Alexander Pushkin...
, from the
Metropolitan Opera HouseThe Metropolitan Opera House was an opera house located at 1411 Broadway in New York City. Opened in 1883 and demolished in 1967, it was the first home of the Metropolitan Opera Company.-History:...
in New York City to 31 theaters across the United States, included a stereophonic sound system developed by
RCARCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
. The first several shows of the 1958–59 season of
The Plymouth Show (AKA
The Lawrence Welk ShowThe Lawrence Welk Show is an American televised musical variety show hosted by big band leader Lawrence Welk. The series aired locally in Los Angeles for four years , then nationally for another 27 years via the ABC network and first-run syndication .In the years since first-run syndication...
) on the
ABCThe American Broadcasting Company is an American commercial broadcasting television network. Created in 1943 from the former NBC Blue radio network, ABC is owned by The Walt Disney Company and is part of Disney-ABC Television Group. Its first broadcast on television was in 1948...
(America) network were broadcast with stereophonic sound in 75
media marketA media market, broadcast market, media region, designated market area , Television Market Area , or simply market is a region where the population can receive the same television and radio station offerings, and may also include other types of media including newspapers and Internet content...
s, with one audio channel broadcast via television and the other over the ABC radio network. By the same method,
NBCThe National Broadcasting Company is an American commercial broadcasting television network and former radio network headquartered in the GE Building in New York City's Rockefeller Center with additional major offices near Los Angeles and in Chicago...
Television and the NBC Radio Network offered stereo sound for two three-minute segments of
The George Gobel Show on October 21, 1958. On January 30, 1959, ABC's
Walt Disney Presents made a stereo broadcast of
The Peter Tchaikovsky Story—including scenes from Disney's latest animated feature,
Sleeping BeautySleeping Beauty is a 1959 American animated film produced by Walt Disney and based on the fairy tale "La Belle au bois dormant" by Charles Perrault...
—by using ABC-affiliated AM and FM stations for the left and right audio channels.
With the advent of FM stereo in 1961, a small number of music-oriented TV shows were broadcast with stereo sound using a process called
simulcastSimulcast, shorthand for "simultaneous broadcast", refers to programs or events broadcast across more than one medium, or more than one service on the same medium, at the same time. For example, Absolute Radio is simulcast on both AM and on satellite radio, and the BBC's Prom concerts are often...
ing, in which the audio portion of the show was carried over a local FM stereo station. In the 1960s and 1970s, these shows were usually manually synchronized with a
reel-to-reel* For the audio technology, see "Reel-to-reel audio tape recording"Reel to Reel is the debut album by Grand Puba. It was Puba's first solo venture, following group projects with the likes of the short lived group Masters of Ceremony and Brand Nubian. Both of the group’s albums were critically...
tape delivered by mail to the FM station (unless the concert or music was locally originated). In the 1980s,
satelliteSatellite television is television programming delivered by the means of communications satellite and received by an outdoor antenna, usually a parabolic mirror generally referred to as a satellite dish, and as far as household usage is concerned, a satellite receiver either in the form of an...
delivery of both television and radio programs made this fairly tedious process of synchronization unnecessary. One of the last of these simulcast programs was
Friday Night VideosFriday Night Videos is an American music video show broadcast on the NBC television network from July 29, 1983 to December 30, 2000, and was the network's attempt to capitalize on the emerging popularity of music videos as seen on MTV...
on NBC, just before
MTS stereoMultichannel television sound, better known as MTS , is the method of encoding three additional channels of audio into an NTSC-format audio carrier.- History :...
was approved by the FCC.
The
BBCThe British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
made extensive use of
simulcastSimulcast, shorthand for "simultaneous broadcast", refers to programs or events broadcast across more than one medium, or more than one service on the same medium, at the same time. For example, Absolute Radio is simulcast on both AM and on satellite radio, and the BBC's Prom concerts are often...
ing between 1974 and around 1990. The first such transmission was in 1974, when the BBC broadcast a recording of Van Morrison's London Rainbow Concert simultaneously on BBC2 TV and Radio 2. After that it was used for many other music programmes, live and recorded, including the annual BBC
Promenade concertsThe Proms, more formally known as The BBC Proms, or The Henry Wood Promenade Concerts presented by the BBC, is an eight-week summer season of daily orchestral classical music concerts and other events held annually, predominantly in the Royal Albert Hall in London...
and the
Eurovision Song ContestThe Eurovision Song Contest is an annual competition held among active member countries of the European Broadcasting Union .Each member country submits a song to be performed on live television and then casts votes for the other countries' songs to determine the most popular song in the competition...
. The advent of
NICAMNear Instantaneous Companded Audio Multiplex is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks...
stereo sound with TV rendered this unnecessary.
Cable TV systems delivered many stereo programs utilizing this method for many years until prices for MTS stereo
modulatorsAn RF modulator is a device that takes a baseband input signal and outputs a radio frequency-modulated signal....
dropped. One of the first stereo cable stations was
The Movie ChannelThe Movie Channel is an American premium channel owned by Showtime Networks, Inc., a subsidiary of CBS Corporation, which shows mostly movies, as well as special behind-the-scenes features, softcore adult erotica and movie trivia....
, though the most popular cable TV station that drove up usage of stereo simulcasting was
MTVMTV, formerly an initialism of Music Television, is an American network based in New York City that launched on August 1, 1981. The original purpose of the channel was to play music videos guided by on-air hosts known as VJs....
.
Japanese television began multiplex (stereo) sound broadcasts in 1978, and regular transmissions with stereo sound came in 1982. By 1984, about 12% of the programming, or about 14 or 15 hours per station per week, made use of the multiplex technology.
West GermanyWest Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....
's second television network,
ZDFZweites Deutsches Fernsehen , ZDF, is a public-service German television broadcaster based in Mainz . It is run as an independent non-profit institution, which was founded by the German federal states . The ZDF is financed by television licence fees called GEZ and advertising revenues...
, began offering stereo programs in 1984.
MTS: Stereo for television
In 1979,
The New York Times reported, "What has prompted the [television] industry to embark on establishing high-fidelity [sound] standards now, according to engineering executives involved in the project, is chiefly the rapid march of the new television technologies, especially those that are challenging broadcast television, such as the
video diskLaserDisc was a home video format and the first commercial optical disc storage medium. Initially licensed, sold, and marketed as MCA DiscoVision in North America in 1978, the technology was previously referred to interally as Optical Videodisc System, Reflective Optical Videodisc, Laser Optical...
."
Multichannel television sound, better known as
MTS (often still as
BTSC, for the Broadcast Television Systems Committee that created it), is the method of
encodingAn encoder is a device, circuit, transducer, software program, algorithm or person that converts information from one format or code to another, for the purposes of standardization, speed, secrecy, security, or saving space by shrinking size.-Media:...
three additional
channelsIn telecommunications and computer networking, a communication channel, or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel...
of
audioSound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
into an
NTSCNTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
-format
audioSound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
carrierIn telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...
. It was adopted by the
FCCThe Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
as the United States
standardStandardization is the process of developing and implementing technical standards.The goals of standardization can be to help with independence of single suppliers , compatibility, interoperability, safety, repeatability, or quality....
for stereo television
transmissionTransmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...
in 1984.
Sporadic network transmission of stereo audio began on NBC on July 26, 1984, with the
Tonight ShowThe Tonight Show Starring Johnny Carson is a talk show hosted by Johnny Carson under the Tonight Show franchise from 1962 to 1992. It originally aired during late-night....
—although at the time, only the network's New York City flagship station,
WNBCWNBC, virtual channel 4 , is the flagship station of the NBC television network, located in New York City. WNBC's studios are co-located with NBC corporate headquarters at 30 Rockefeller Plaza in midtown Manhattan...
, had stereo broadcast capability. Regular stereo transmission of programs began in 1985.
A-B technique: time-of-arrival stereophony
This uses two parallel omnidirectional microphones some distance apart, capturing time-of-arrival stereo information as well as some level (amplitude) difference information—especially if employed in close proximity to the sound source(s). At a distance of about 60 cm (23 inches), the time delay (time-of-arrival difference) for a signal reaching the first microphone and then the other one from the side is approximately 1.5 msec (1 to 2 msec). If you increase the distance between the microphones, you effectively decrease the pickup angle. At a 70 cm (27 inches) distance, it is approximately equivalent to the pickup angle of the near-coincident ORTF setup.
This technique can produce phase issues when the stereo signal is mixed to mono.
X-Y technique: intensity stereophony
Here, two directional
microphoneA microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
s are at the same place, typically pointing at an angle between 90° and 135° to each other. The stereo effect is achieved through differences in sound pressure level between two microphones. A difference in levels of 18 dB (16 to 20 dB) is needed for hearing the direction of a loudspeaker. Due to the lack of differences in time-of-arrival/phase ambiguities, the sonic characteristic of X-Y recordings has less sense of space and depth when compared to recordings employing an A-B setup. When two figure-eight microphones are used, facing ±45° with respect to the sound source, the X-Y setup is called a
Blumlein PairBlumlein Pair is the name for a stereo recording technique invented by Alan Blumlein for the creation of recordings that, upon replaying through headphones or loudspeakers, recreate the spatial characteristics of the recorded signal....
. The sonic image produced is realistic, almost "holographic".
M/S technique: Mid/Side stereophony
This coincident technique employs a bidirectional microphone facing sideways and another microphone at an angle of 90°, facing the sound source. The second microphone is generally a variety of cardioid, although
Alan BlumleinAlan Dower Blumlein was a British electronics engineer, notable for his many inventions in telecommunications, sound recording, stereo, television and radar...
described the usage of an omnidirectional transducer in his original patent.
The left and right channels are produced through a simple matrix: Left = Mid + Side; Right = Mid − Side (the polarity-reversed side signal). This configuration produces a completely mono-compatible signal and, if the Mid and Side signals are recorded (rather than the matrixed Left and Right), the stereo width can be manipulated after the recording has taken place. This makes it especially useful for film-based projects.
Near-coincident technique: mixed stereophony
These techniques combine the principles of both A-B and X-Y (coincident pair) techniques. For example, the
ORTF stereo techniqueThe ORTF stereo microphone system is a microphone technique used to record stereo sound.It was devised around 1960 at the Office de Radiodiffusion Télévision Française at Radio France....
of the
Office de Radiodiffusion Télévision FrançaiseThe Office de Radiodiffusion-Télévision Française was the national agency charged, between 1964 and 1974, with providing public radio and television in France.-Post World War II:...
(
Radio FranceRadio France is a French public service radio broadcaster.-Mission:Radio France's two principal missions are:* To create and expand the programming on all of their stations; and...
) calls for a pair of cardioid microphones placed 17 cm apart at a total angle between microphones of 110°, which results in a stereophonic pickup angle of 96° (
Stereo Recording Angle, or SRA). In the
NOS stereo techniqueThe NOS stereo microphone system is a very useful device to capture a stereo sound.The Nederlandse Omroep Stichting NOS = Holland Radio found by a number of practical attempts a stereo main microphone system, which results in a quite even distribution of the phantom sources on the stereo...
of the Nederlandse Omroep Stichting (Holland Radio), the total angle between microphones is 90° and the distance is 30 cm, thus capturing time-of-arrival stereo information as well as level information. It is noteworthy that all spaced microphone arrays and all near-coincident techniques use a spacing of at least 17 cm or more. 17 cm roughly equals the human ear distance and therefore provides the same interaural time difference (ITD) or more, depending on the spacing between microphones. Although the recorded signals are generally intended for playback over stereo loudspeakers, reproduction over headphones can provide remarkably good results, depending on the microphone arrangement.
Pseudo-stereo
In the course of restoration or remastering of
monophonicMonaural or monophonic sound reproduction is single-channel. Typically there is only one microphone, one loudspeaker, or channels are fed from a common signal path...
records, various techniques of "pseudo-stereo", "quasi-stereo", or "rechanneled stereo" have been used to create the impression that the sound was originally recorded in stereo. These techniques first involved hardware methods (see
Duophonic*In synthesizers, capable of sounding two voices, or notes, at a time. Compare: monophonic, polyphonic.*Duophonic is also a term used to refer to a sound process by which a monaural recording is turned into a kind of "fake stereo" by splitting the signal into two channels, delaying the left and the...
) or, more recently, a combination of hardware and software. Multitrack Studio, from Bremmers Audio Design (The Netherlands), uses special filters to achieve a pseudo-stereo effect: the "shelve" filter directs low frequencies to the left channel and high frequencies to the right channel, and the "comb" filter adds a small delay in signal timing between the two channels, a delay barely noticeable by ear,
[The comb filter allows range of manipulation between 0 and 100 milliseconds.] but contributing to an effect of "widening" original "fattiness" of mono recording.
The special pseudo-stereo circuit—invented by Kishii and Noro, from Japan—was patented in the United States in 2003, with already previously issued patents for similar devices. Artificial stereo techniques have been used to improve the listening experience of monophonic recordings or to make them more "saleable" in today's market, where people expect stereo. Some critics have expressed concern about the use of these methods.
Binaural recording
Engineers make a technical distinction between "binaural" and "stereophonic" recording. Of these,
binaural recordingBinaural 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 often created using a technique known as "Dummy head...
is analogous to
stereoscopic photographyStereoscopy refers to a technique for creating or enhancing the illusion of depth in an image by presenting two offset images separately to the left and right eye of the viewer. Both of these 2-D offset images are then combined in the brain to give the perception of 3-D depth...
. In binaural recording, a pair of microphones is put inside a model of a human head that includes external ears and ear canals; each microphone is where the
eardrumThe eardrum, or tympanic membrane, is a thin membrane that separates the external ear from the middle ear in humans and other tetrapods. Its function is to transmit sound from the air to the ossicles inside the middle ear. The malleus bone bridges the gap between the eardrum and the other ossicles...
would be. The recording is then played back through headphones, so that each channel is presented independently, without mixing or crosstalk. Thus, each of the listener's eardrums is driven with a replica of the auditory signal it would have experienced at the recording location. The result is an accurate duplication of the auditory spatiality that would have been experienced by the listener had he or she been in the same place as the model head. Because of the inconvenience of wearing headphones, true binaural recordings have remained laboratory and audiophile curiosities. However "loudspeaker-binaural" listening is possible with
AmbiophonicsAmbiophonics is a method in the public domain that employs digital signal processing and two loudspeakers directly in front of the listener in order to improve reproduction of stereophonic and 5.1 surround sound for music, movies, and games in home theaters, gaming PCs, workstations, or studio...
.
Playback
Stereophonic sound attempts to create an illusion of location for various sound sources (voices, instruments, etc.) within the original recording. The recording engineer's goal is usually to create a stereo "image" with localization information. When a stereophonic recording is heard through loudspeaker systems (rather than headphones), each ear, of course, hears sound from both speakers. The audio engineer may, and often does, use more than two microphones (sometimes many more) and may mix them down to two tracks in ways that exaggerate the separation of the instruments, in order to compensate for the mixture that occurs when listening via speakers.
Descriptions of stereophonic sound tend to stress the ability to localize the position of each instrument in space, but this would only be true in a carefully engineered and installed system, where speaker placement and room acoustics are taken into account. In reality, many playback systems, such as all-in-one boombox units and the like, are incapable of recreating a realistic stereo image. Originally, in the late 1950s and 1960s, stereophonic sound was marketed as seeming "richer" or "fuller-sounding" than monophonic sound, but these sorts of claims were and are highly subjective, and again, dependent on the equipment used to reproduce the sound. In fact, poorly recorded or reproduced stereophonic sound can sound far worse than well done monophonic sound. When playing back stereo recordings, the best results are obtained by using two identical speakers, in front of and equidistant from the listener, with the listener located on a center line between the two speakers. In effect, an
equilateral triangle is formed, with the angle between the two speakers around 60 degrees as seen from the listener's point of view.
Vinyl records
In 1958, the first group of mass-produced stereo two-channel records was issued, by Audio Fidelity in the USA and Pye in Britain, using the Westrex "45/45" single-groove system. Whereas the stylus moves horizontally when reproducing a monophonic disk recording, on stereo records, the stylus moves vertically as well as horizontally. One could envision a system in which the left channel was recorded laterally, as on a monophonic recording, with the right channel information recorded with a "hill and dale" vertical motion; such systems were proposed but not adopted, due to their incompatibility with existing phono pickup designs (see below). In the Westrex system, each channel drives the cutting head at a 45-degree angle to the vertical. During playback, the combined signal is sensed by a left-channel coil mounted diagonally opposite the inner side of the groove and a right-channel coil mounted diagonally opposite the outer side of the groove. The Westrex system provided for the polarity of one channel to be inverted: this way large groove displacement would occur in the horizontal plane and not in the vertical one. The latter would require large up-and-down excursions and would encourage cartridge skipping during loud passages.
The combined stylus motion is, in terms of the vector, the sum and difference of the two stereo channels. Effectively, all horizontal stylus motion conveys the L+R sum signal, and vertical stylus motion carries the L−R difference signal. The advantages of the 45/45 system are that it has greater compatibility with monophonic recording and playback systems. A monophonic cartridge will reproduce an equal blend of the left and right channels, instead of reproducing only one channel. Conversely, a stereo cartridge reproduces the lateral grooves of monophonic recording equally through both channels, rather than one channel. Also, it gives a more balanced sound, because the two channels have equal fidelity as opposed to providing one higher-fidelity laterally recorded channel and one lower-fidelity vertically recorded channel. Overall, this approach may give higher fidelity, because the "difference" signal is usually of low power, and is thus less affected by the intrinsic distortion of "hill and dale"-style recording.
This system was invented by
Alan BlumleinAlan Dower Blumlein was a British electronics engineer, notable for his many inventions in telecommunications, sound recording, stereo, television and radar...
of
EMIThe EMI Group, also known as EMI Music or simply EMI, is a multinational music company headquartered in London, United Kingdom. It is the fourth-largest business group and family of record labels in the recording industry and one of the "big four" record companies. EMI Group also has a major...
in 1931 and was patented the same year. EMI cut the first stereo test discs using the system in 1933, but it was not applied commercially until a quarter of a century later. Stereo sound provides a more natural listening experience, since the spatial location of the source of a sound is (at least in part) reproduced. In the 1960s, it was common practice to generate stereo versions of music from monophonic master tapes, which were normally marked "electronically reprocessed" or "electronically enhanced" stereo on track listings. These were generated by a variety of processing techniques to try to separate out various elements; this left noticeable and unsatisfactory artifacts in the sound, typically sounding "phasey". However, as multichannel recording became increasingly available, it has become progressively easier to master or remaster more plausible stereo recordings out of the archived multitrack master tapes.
Compact disc
The
Red Book CDRed Book is the standard for audio CDs . It is named after one of the Rainbow Books, a series of books that contain the technical specifications for all CD and CD-ROM formats.The first edition of the Red Book was released in 1980 by Philips and Sony; it was adopted by the Digital Audio Disc...
specification includes two channels by default, and so a mono recording on CD either has one empty channel, or else the same signal being relayed to both channels simultaneously.
Radio
In
FM broadcastingFM broadcasting is a broadcasting technology pioneered by Edwin Howard Armstrong which uses frequency modulation to provide high-fidelity sound over broadcast radio. The term "FM band" describes the "frequency band in which FM is used for broadcasting"...
, the Zenith-GE pilot-tone stereo system is used throughout the world.
Because of the limited audio quality of the majority of AM receivers, and also because AM stereo receivers are relatively scarce, relatively few AM stations employ stereo. Various modulation schemes are used for
AM stereoAM stereo is a term given to a series of mutually incompatible techniques for wireless radio broadcasting stereo audio in the AM band in a manner that is compatible with standard AM receivers...
, of which the best-known is
MotorolaMotorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...
's
C-QUAMC-QUAM is the method of AM stereo broadcasting used in Canada, the United States and most other countries. It was invented in 1977 by Norman Parker, Francis Hilbert, and Yoshio Sakaie, and published in an IEEE journal....
, the official method for most countries in the world that transmit in AM stereo. More AM stations are adopting digital
HD RadioHD Radio, which originally stood for "Hybrid Digital", is the trademark for iBiquity's in-band on-channel digital radio technology used by AM and FM radio stations to transmit audio and data via a digital signal in conjunction with their analog signals...
, which allows the transmission of stereo sound on AM stations. For Digital Audio Broadcasting,
MP2MPEG-1 Audio Layer II or MPEG-2 Audio Layer II is a lossy audio compression format defined by ISO/IEC 11172-3 alongside MPEG-1 Audio Layer I and MPEG-1 Audio Layer III...
audio streams are used. DAB is one of the Digital Radio formats that is used to broadcast Digital Audio over terrestrial broadcast networks or satellite networks. DAB is extended to video, and the new format is called
DMBDigital Multimedia Broadcasting is a digital radio transmission technology developed in South Korea as part of the national IT project for sending multimedia such as TV, radio and datacasting to mobile devices such as mobile phones...
.
Television
For analog TV (PAL and NTSC), various modulation schemes are used in different parts of the world to broadcast more than one sound channel. These are sometimes used to provide two mono sound channels that are in different languages, rather than stereo.
Multichannel television soundMultichannel television sound, better known as MTS , is the method of encoding three additional channels of audio into an NTSC-format audio carrier.- History :...
is used mainly in the Americas.
NICAMNear Instantaneous Companded Audio Multiplex is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks...
is widely used in Europe, except in Germany, where
ZweikanaltonZweikanalton is a television sound transmission system used in Germany, Austria, Switzerland, and other countries that use or used PAL-B or PAL-G...
is used. The EIAJ FM/FM subcarrier system is used in Japan. For Digital TV, MP2 audio streams are widely used within MPEG-2 program streams.
Common usage
In common usage, a "stereo" is a two-channel sound reproduction system, and a "stereo recording" is a two-channel recording. This is cause for much confusion, since five (or more)-channel
home theaterHome 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 are not popularly described as "stereo". It is thus worth noting that most film soundtracks are not recorded using stereo techniques; so while they are capable of stereo reproduction, most home theater systems are rarely called upon to do this.
Most two-channel recordings are stereo recordings only in this weaker sense. Pop music, in particular, is usually recorded using close miking techniques, which artificially separate signals into several tracks. The individual tracks (of which there may be hundreds) are then "mixed down" into a two-channel recording. By using "left-right" panning controls, the audio engineers determine where each track will be placed in the stereo "image". The end product using this process often bears little or no resemblance to the actual physical and spatial relationship of the musicians at the time of the original performance; indeed, it is not uncommon for different tracks of the same song to be recorded at different times (and even in different studios) and then mixed into a final two-channel recording for commercial release.
Classical music recordings are a notable exception. They are more likely to be recorded "live", so that the actual physical and spatial relationship of the musicians at the time of the original performance is preserved on the recording.
Balance
Balance can mean the amount of signal from each channel reproduced in a stereo audio recording. Typically, a balance control in its center position will have 0
dBThe decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
of gain for both channels and will attenuate one channel as the control is turned, leaving the other channel at 0 dB.
See also PanningPanning is the spread of a sound signal into a new stereo or multi-channel sound field. A typical physical recording console pan control is a knob with a pointer which can be placed from the 8 o'clock dial position fully left to the 4 o'clock position fully right...
.
See also
- 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...
- Ambiophonics
Ambiophonics is a method in the public domain that employs digital signal processing and two loudspeakers directly in front of the listener in order to improve reproduction of stereophonic and 5.1 surround sound for music, movies, and games in home theaters, gaming PCs, workstations, or studio...
– binaural with speakers, not headphones
- 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...
– generalized MS-Stereo to three dimensions
- 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...
– The physically reconstruction of the spatial sonic field
- 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 often created using a technique known as "Dummy head...
- Blumlein Pair
Blumlein Pair is the name for a stereo recording technique invented by Alan Blumlein for the creation of recordings that, upon replaying through headphones or loudspeakers, recreate the spatial characteristics of the recorded signal....
- Crossfeed
Crossfeed is the process of blending the left and right channels of a stereo audio recording. It is generally used to reduce the extreme channel separation often featured in early stereo recordings , or to make audio played through headphones sound more natural, as when listening to a pair of...
- Hi-fi
- Joint stereo
- 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...
- Stereo photography
- Stereographic projection
The stereographic projection, in geometry, is a particular mapping that projects a sphere onto a plane. The projection is defined on the entire sphere, except at one point — the projection point. Where it is defined, the mapping is smooth and bijective. It is conformal, meaning that it...
- 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...
(Stereo separation)
- Surround sound
Surround sound encompasses a range of techniques such as for enriching the sound reproduction 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...
External links