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An Intrstng Exprmnt in Spch
January 1957 Radio & Television News Article

January 1957 Radio & Television News
January 1957 Radio & Television News Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio & Television News, published 1919 - 1959. All copyrights hereby acknowledged.

Here is a little insight into early speech processing research by the Bell Telephone Laboratories. 1957 was the early era of real-time digital processing where the need to cram more calls into less signal space (bandwidth) led to sampled systems - 1:6 in the case of this advertisement from Bell that appeared in Radio & Television News. Engineers of the day would be amazed at how the state of the art has advanced since then, both in mathematical techniques and in miniaturized hardware.

An Intrstng Exprmnt in Spch

Vibrations of the sound "or" in the word "four" - RF Cafe
Vibrations of the sound "or" in the word "four." Pattern represents nine of the "pitch periods" which originate in puffs of air from the larynx when a word is spoken.

An electronic sampling of the "or" sound - RF Cafe
An electronic sampling of the "or" sound. One "pitch period" in three has been selected for transmission. This permits great naturalness when voice is rebuilt. Intelligible speech could be sent through a 1 in 6 sampling.

The selected samples are "stretched" for transmission - RF Cafe
The selected samples are "stretched" for transmission. They travel in a narrower frequency band than complete sound.

Using the stretched sample as a model - RF Cafe
Using the stretched sample as a model, the receiver restores original frequency. In all speech, sounds are intoned much longer than is needed for recognition - even by the human ear. Electronic machines perform recognition far faster than the ear.

The receiver fills in gaps between samples - RF Cafe
The receiver fills in gaps between samples, recreating total original sound. Under new system, three or four voices could travel at once over a pair of wires which now carries only one - and come out clearly at the end!
Some day your voice may travel by a sort of electronic "shorthand" when you telephone. Bell Laboratories scientists are experimenting with a technique in which a sample is snipped off a speech sound - just enough to identify it - and sent by wire to a receiver which rebuilds the original sound. Thus voices can be sent by means of fewer signals. More voices may economically share the wires.

This is but one of many transmission techniques that Laboratories scientists are exploring in their search for ways to make Bell System wire and radio channels serve you more efficiently. It is another example of the Bell Telephone Laboratories research that keeps your telephone the most advanced on earth. The oscilloscope traces at right show how the shorthand technique works.

Bell Telephone Laboratories Logo - RF Cafe

World center of communications research
Largest industrial laboratory in the United States

     Original full-page Bell Telephone Laboratories advertisement - RF Cafe
Original full-page Bell Telephone Laboratories advertisement

Posted  6/20/2013

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