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1939 __ Voder, Vocoder
Homer W. Dudley (1896-1987)
Comment : Howard Duddley was a pioneering electronic and acoustic engineer who created the first electronic voice synthesizer for Bell Labs in the 1930s and led the development of a method of sending secure voice transmissions during World War Two. Dudley's primary area of exploration was in the idea of human speech being fundamentally the use of a carrier -- a more or less continuous sound that is modulated and shaped by the mouth, throat and sinuses into recognizable speech. The vocal cords create a carrier sound which is shaped into formants by the throat, mouth and sinuses into what we recognize as vowel sounds ("aah", "eeh", "ooh", etc.), which are further shaped by plosives (such as pressing the lips together to create a "p" sound) and glottal stops (such as closing the back of the throat to produce a "guh" sound). Dudley theorized that an intelligible analogue to human speech could be created by breaking sound down into modular blocks which could be assembled into a desired order, to allow the production and communication with artificial speech. By replacing the natural carrier sound of human speech with a carrier sound at a higher frequency, speech could be reproduced more clearly over long distances and low volumes, since higher frequency sounds are heard more clearly than lower ones. n 1928, Dudley began experimenting with electromechanical devices to produce analogues of human speech. A key to this process was the development of a parallel band-pass filter, which allowed sounds to be filtered down to a fairly specific portion of the audio spectrum by attenuating the sounds that fall above or below a certain band. This led to the patent for the "Vocoder" (a portmanteau of "voice" and "encoder"), a method of reproducing speech through electronic means, and allowing it to be transmitted over distances, as through telephone lines. By reproducing human speech electronically, the elements of speech could filtered into ten specific audio spectrum bands, rendering it more easily transmitted over telephone lines with greater clarity and legibility. The speech could also be compressed down to a very narrow frequency band, to allow multiple transmissions simultaneously on different bands. This enabled many telephone conversations to be transmitted at the same time over one line. With the assistance of fellow engineer Richard Riesz, Dudley created the "VODER" (another portmanteau, for "Voice Operation DEmonstratoR"), a console from which an operator could create phrases of speech controlling a VOCODER with a keyboard and foot pedals; it was considered difficult to operate. The VODER was demonstrated at Bell Laboratory exhibits at both the 1939 New York World's Fair and the 1939 Golden Gate International Exposition. With a woman operator sitting behind the console, phrases resembling human speech could be demonstrated to the audience, although the produced sounds were often difficult to understand. On June 21, 1938 Dudley and Bell Labs were granted a patent (US#2,121,142) for a "System for the artificial production of vocal or other sounds". Dudley worked with famed British mathematician, cryptographer and computer pioneer Alan Turing on the SIGSALY project, for the US Military. SIGSALY was a method of transmitting speech in a secure manner, rendering it unable to be understood by unauthorized listeners. It utilized technology developed in the VOCODER and VODER projects, and added a random noise source as a method of encrypting speech. SIGSALY was successfully used by US military intelligence during World War II for transmitting the highest level of classified messages. One of Dudley's final projects was the design of an electronic kit distributed by Bell Labs for home hobbyists and students, called "Speech Synthesis: an Experiment in Electronic Speech Production". The kit contained the components with which to create an electronic circuit that could produce three different speech formants. The kit entered production in 1963 and was produced until the late 1960s. (Compiled from various sources)"Parallel Bandpass Vocoder" (1939) Homer.W. Dudley: speech analysis and resynthesis. "The Voder speech synthesizer"(1940) Homer.W. Dudley: a voice model played by a human operator.The Vocoder (Voice Operated reCorDER) developed by Homer Dudley, a research physicist at Bell Laboratories, New Jersey USA, was a composite device consisting of an analyser and an artificial voice. The analyser detected energy levels of succesive sound samples measured over the entire audio frequency spectrum via a series of narrow band filters. The results of which could be viewed graphically as functions of frequency against time. The synthesiser reversed the process by scanning the data from the analyser and supplying the results to a feedback network of analytical filters energised by a noise generator to produce audible sounds. The fidelity of the machine was limited, the machine was intended as a research machine for compression schemes to transmit voice over copper phone lines. Werner Meyer-Eppler, then the director of Phonetics at Bonn University, recognised the relevance of the machines to electronic music after Dudley visited the University in 1948, and used the vocoder as a basis for his future writings which in turn became the inspiration for the German "Electronische Musik" movement. "At the 1939 World's Fair a machine called a Voder was shown . A girl stroked its keys and it emitted recognisable speech. No human vocal cords entered into the procedure at any point; the keys simply combined some electronically produced vibrations and passed these on to a loud-speaker." ("As We May Think" by Vannevar Bush, 1945. ). (Simon Crab)
French comment : Invention du Voder et surtout du Vocoder (Voice Operated reCOrDER) par Homer Dudley, au départ pour une utilisation non musicale. En 1948, il en fera pourtant une démonstration aux studios de la WDR pour Werner Meyer-Eppler. Ce dernier utilise en 1949 un enregistrement du Vocoder pour illustrer sa conférence : "Developmental Possibilities of Sound". (Compiled from various sources)
Urls : http://ptolemy.eecs.berkeley.edu/~eal/audio/vocoder.html (last visited ) http://120years.net/machines/vocoder/ (last visited )

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