Homer Dudley
Encyclopedia
Homer W. Dudley 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 family moved to Pennsylvania
when he was a schoolboy. His father was a preacher, and his parents also gave lessons to students, in classical and religious subjects. Dudley trained to be a grade school and high school teacher
. He found it difficult to keep discipline in the classroom and soon gave up teaching. Intending a change in career, he enrolled in Pennsylvania State University
, where he developed an interest in the nascent science of electronic engineering. After taking some college courses in electronic engineering, Dudley found employment with Bell Laboratories, which was at that time a division of Western Electric Company. His career with Bell Labs spanned 40 years, most of it in the Telephone Transmission Division.
-- 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.
, 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".
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.
, Robert Moog
and the German musical group Kraftwerk
. 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.
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
in the 1930s and led the development of a method of sending secure voice transmissions during World War Two.
Early life
Born in VirginiaVirginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
, Dudley's family moved to Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
when he was a schoolboy. His father was a preacher, and his parents also gave lessons to students, in classical and religious subjects. Dudley trained to be a grade school and high school teacher
Teacher
A teacher or schoolteacher is a person who provides education for pupils and students . The role of teacher is often formal and ongoing, carried out at a school or other place of formal education. In many countries, a person who wishes to become a teacher must first obtain specified professional...
. He found it difficult to keep discipline in the classroom and soon gave up teaching. Intending a change in career, he enrolled in Pennsylvania State University
Pennsylvania State University
The Pennsylvania State University, commonly referred to as Penn State or PSU, is a public research university with campuses and facilities throughout the state of Pennsylvania, United States. Founded in 1855, the university has a threefold mission of teaching, research, and public service...
, where he developed an interest in the nascent science of electronic engineering. After taking some college courses in electronic engineering, Dudley found employment with Bell Laboratories, which was at that time a division of Western Electric Company. His career with Bell Labs spanned 40 years, most of it in the Telephone Transmission Division.
Sound theory
Dudley's primary area of exploration was in the idea of human speech being fundamentally the use of a carrierCarrier wave
In 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...
-- 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
Vowel
In phonetics, a vowel is a sound in spoken language, such as English ah! or oh! , pronounced with an open vocal tract so that there is no build-up of air pressure at any point above the glottis. This contrasts with consonants, such as English sh! , where there is a constriction or closure at some...
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.
The VOCODER and VODER
In 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 filterBand-pass filter
A band-pass filter is a device that passes frequencies within a certain range and rejects frequencies outside that range.Optical band-pass filters are of common usage....
, 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
Vocoder
A vocoder is an analysis/synthesis system, mostly used for speech. In the encoder, the input is passed through a multiband filter, each band is passed through an envelope follower, and the control signals from the envelope followers are communicated to the decoder...
" (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
Telephone
The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...
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
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the 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
1939 New York World's Fair
The 1939–40 New York World's Fair, which covered the of Flushing Meadows-Corona Park , was the second largest American world's fair of all time, exceeded only by St. Louis's Louisiana Purchase Exposition of 1904. Many countries around the world participated in it, and over 44 million people...
and the 1939 Golden Gate International Exposition
Golden Gate International Exposition
The Golden Gate International Exposition , held at San Francisco, California's Treasure Island, was a World's Fair that celebrated, among other things, the city's two newly-built bridges. The San Francisco – Oakland Bay Bridge was dedicated in 1936 and the Golden Gate Bridge was dedicated in 1937...
. 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".
SIGSALY and wartime projects
Dudley worked with famed BritishUnited Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
, cryptographer and computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
pioneer Alan Turing
Alan Turing
Alan Mathison Turing, OBE, FRS , was an English mathematician, logician, cryptanalyst, and computer scientist. He was highly influential in the development of computer science, providing a formalisation of the concepts of "algorithm" and "computation" with the Turing machine, which played a...
on the SIGSALY
SIGSALY
In cryptography, SIGSALY was a secure speech system used in World War II for the highest-level Allied communications....
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
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
for transmitting the highest level of classified messages.
Later projects
Dudley stayed with Bell Labs through the early 1960s. During that time, he invented and refined many of the technologies that became essential for telephony. His development of artificial speech was elaborated upon by others to produce methods of artificial speech for humans unable to use their vocal cords (as with the voice synthesizer used by Steven Hawking), and by electronic music pioneers Wendy CarlosWendy Carlos
Wendy Carlos is an American composer and electronic musician. Carlos first came to notice in the late 1960s with recordings made on the Moog synthesizer, then a relatively new and unknown instrument; most notable were LPs of synthesized Bach and the soundtrack for Stanley Kubrick's film A...
, Robert Moog
Robert Moog
Robert Arthur Moog , commonly called Bob Moog was an American pioneer of electronic music, best known as the inventor of the Moog synthesizer.-Life:...
and the German musical group Kraftwerk
Kraftwerk
Kraftwerk is an influential electronic music band from Düsseldorf, Germany. The group was formed by Ralf Hütter and Florian Schneider in 1970, and was fronted by them until Schneider's departure in 2008...
. 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.