Monday, December 08, 2008

Someone did invent Stereo

We take the stereophonic listening experience, with images between two loudspeakers and it's convincing illusion of width and depth for granted, but it has been used commercially for less than fifty years. It is also very interesting to note that many of the advancements in this area were fuelled by motion pictures. People were seen to move from left to right, and the sound should match. Sound is understood as an enveloping experience, and --simplifying a bit-- along comes Surround...
  • 1857
    Monaural sound is first transcribed by Édouard-Léon Scott de Martinville
  • 1877
    Thomas Edison's phonograph cylinder enables the recording & playback of sound
  • 1880
    Stereophonic sound, realized by Clément Ader, has a cursory appearance
  • 1930
    Binaural Sound is studied in depth by Alan Dower Blumlein and Arthur C. Keller
  • 1960
    The age of Stereo begins
  • 1970
    RCA Records introduces Quadraphonic sound
  • 1970
    Michael Gerzon extends on Blumlein's work with the development of Ambisonics
  • 1970
    Walter Murch thinks up 5.1-Surround for "Apocalypse Now"
Alan Dower Blumlein, born on June 29, 1903 in Hampstead, London, invented two out of the three "pure" techniques for recording sound in stereo [stereos = "solid" and phōnē = "sound"]: XY (subsuming the special case of the Blumlein-configuration) and M/S. Both are termed coincident stereophony because the capsules of the two microphones involved are located at (about) the same spot. Blumlein's work has a profound influence on Michael Gerzon who developed Ambisonics as a followup to Quadraphonics.

The third traditional approach to recording in stereo, AB-stereophonics, is based not on differences in the sound pressure level of signals reaching the two microphones but rather on differences in time-of arrival (or the "runtime" or phase) of the signals. It was developed at Bell Labs by Arthur C. Keller under the supervision of Dr. Harvey Fletcher. Stokowski was delighted: ''Listening monaurally,'' he reported to Bell Laboratories, ''gives me the sensation of the music being choked and crushed together. Binaurally (i.e., in stereo) the music sounds free, spacious, and the choked sensation is gone." [Link]

Coincident and runtime-based configurations give rise to near-coincident techniques, one of the most mentionable being ORTF, developed by and named for the Office de Radiodiffusion Télévision Française.

5.1 for Apocalypse Now?

Movie-sound before the 1970's mainly utilized stereo, plus an effects channel at the rear of the audience. Walter Murch wanted to be able to spread the rear ambience to better enfold the listeners. And then there was the matter of the voiceovers...

The target of "Apocalypse Now", big movie theaters, were not suited for Quadraphonic playback. With stereo there is a more or less defined sweet spot in the center between the two speakers. If the voice of the actors or a disembodied voiceover came from the phantom-middle, that is if it were mixed into the front left and front right stream in equal parts, it would appear to come from the side the audience were located on. Members of the the audience on the far left would hear the voice coming from there. Placing a center speaker behind and in the middle of the big screen anchors the voice to that position more firmly.

The establishment of this setup as a mainstream commodity doesn't mean recordings have to be made with an explicit 5.1-mapping though. But this is (yet) another topic, to be discussed soon :-)

[Thanks to the Wikipedia & Steven Schoenherr]

[100204 - Quadraphonic sound came before Ambisonics]

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