Stereophonic sound

This is usually achieved by using two independent audio channels through a configuration of two loudspeakers (or stereo headphones) in such a way as to create the impression of sound heard from various directions, as in natural hearing.

Stereo sound has been in common use since the 1970s in entertainment media such as broadcast radio, recorded music, television, video cameras, cinema, computer audio, and the Internet.

The sound reproduction systems of the early talkies invariably only had a single set of speakers – which could lead to the somewhat disconcerting effect of the actor being on one side of the screen whilst his voice appeared to come from the other.

In 1934, Blumlein recorded Mozart's Jupiter Symphony conducted by Sir Thomas Beecham at Abbey Road Studios in London using his vertical-lateral technique.

[citation needed] Later that same year, Bell Labs also demonstrated binaural sound, at the Chicago World's Fair in 1933 using a dummy with microphones instead of ears.

[13] Utilizing selections recorded by the Philadelphia Orchestra, under the direction of Leopold Stokowski, intended for but not used in Walt Disney's Fantasia, the Carnegie Hall demonstration by Bell Laboratories on April 9 and 10, 1940, used three huge speaker systems.

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.[15] Once again, conductor Leopold Stokowski was on hand to try out the new technology, recording onto a special proprietary nine-track sound system at the Academy of Music in Philadelphia, during the making of the movie One Hundred Men and a Girl for Universal Pictures in 1937, after which the tracks were mixed down to one for the final soundtrack.

[19][20] The film was not initially a financial success, however, after two months of road-show exhibition in selected cities, its soundtrack was remixed into mono sound for general release.

The Cinerama audio soundtrack technology, developed by Hazard E. Reeves, utilized seven discrete sound tracks on full-coat magnetic 35 mm film.

By the early 1950s, all of the major studios were recording on 35 mm magnetic film for mixing purposes, and many of these so-called individual angles still survive, allowing for soundtracks to be remixed into stereo or even surround.

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 House of Wax, an early 3-D film starring Vincent Price and produced by Warner Bros.

In addition, a large percentage of 3-D films carried variations on three-track magnetic sound: It Came from Outer Space; I, the Jury; The Stranger Wore a Gun; Inferno; Kiss Me, Kate; and many others.

Inspired by Cinerama, the movie industry moved quickly to create simpler and cheaper widescreen systems, the first of which, Todd-AO, was developed by Broadway promoter Michael Todd with financial backing from Rodgers and Hammerstein, to use a single 70 mm film running at 30 frames per second with 6 magnetic soundtracks, for their screen presentation of Oklahoma!.

Major Hollywood studios immediately rushed to create their own unique formats, such as MGM's Camera 65, Paramount Pictures' VistaVision and Twentieth Century-Fox Film Corporation's CinemaScope, the latter of which used up to four separate magnetic soundtracks.

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, featured the film printed down to 70 mm with a six-channel soundtrack.

The progress of stereophonic sound was paced by the technical difficulties of recording and reproducing two or more channels in synchronization with one another and by the economic and marketing issues of introducing new audio media and equipment.

After 33+1⁄3 RPM recording had been perfected for the movies in 1927, the speed of radio program transcriptions was reduced to match, once again to inhibit playback of the discs on normal home consumer equipment.

Over a quarter of a century later, it was decided to tilt the recording head 45 degrees off to the right side so that both the low-frequency rumble and high-frequency distortion were shared equally by both channels, producing the 45/45 system we know today.

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, took the two-channel high-fidelity system described above and developed a binaural[note 1] record out of it.

8 directed by Herbert von Karajan and the Orchester der Berliner Staatsoper and a 1944 or 1945 recording of Walter Gieseking playing Beethoven's Piano Concerto No.

Sidney Frey, founder and president, had Westrex engineers, owners of one of the two rival stereo disk-cutting systems, cut a disk for release before any of the major record labels could do so.

With the supplied special turntables featuring a clear platter lighted from underneath to show off the color as well as the sound, the stunt worked even better for Bel Canto, whose roster of jazz, easy listening and lounge music, pressed onto their trademark Caribbean-blue vinyl sold well throughout 1958 and early into 1959.

That same year Doolittle began a year-long series of test transmissions, using his medium wave broadcasting station, WPAJ in New Haven, Connecticut, which was temporarily authorized to concurrently operate a second transmitter.

[60] The revived dual transmitter tests were of limited success, because they still required two receivers, and with AM-FM pairings the sound quality of the AM transmissions was generally significantly inferior to the FM signals.

[62] At midnight in their respective time zones on June 1, General Electric's WGFM in Schenectady, New York, Zenith's WEFM in Chicago, and KMLA in Los Angeles became the first three stations to begin broadcasting using the new stereo standards.

A December 11, 1952, closed-circuit television performance of Carmen from the Metropolitan Opera House in New York City to 31 theaters across the United States, included a stereophonic sound system developed by RCA.

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.

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.

The audio engineers determine where each track will be placed in the stereo "image", by using various techniques that may vary from very simple (such as "left-right" panning controls) to more sophisticated and extensively based on psychoacoustic research (such as channel equalization, mid-side processing, and the use of delay to exploit the precedence effect).