What Makes the Picture Talk: AT&T and the
Development of Sound Motion Picture Technology

By Sheldon Hochheiser, Ph.D.
Corporate Historian, AT&T Labs
Edward C. Wente

Edward C. Wente
Edward Christopher Wente joined the Western Electric Engineering Department in 1914 to work on research involving the design and calibration of a uniformly sensitive transmitter (or microphone) for use in sound studies. The carbon-button transmitters used in telephone receivers had too uneven a frequency response and too much background noise for sound research. With Harold D. Arnold’s amplifier available to augment the extremely weak signals, Wente in 1916 turned to a previously useless device known as an electrostatic transmitter into the first flat frequency response microphone or, as Wente called it, the condenser transmitter. He published his results in a theoretical paper in The Physical Review the following year. In 1922, he produced a condenser transmitter with one hundred times greater sensitivity, which was enough to make it a practical device, although its high impedance required its direct connection to a vacuum tube preamplifier without long intervening wires.

Researchers in the sound studies also needed to record and reproduce sound. Phonographs of the era were acoustic-mechanical devices that were too limited and uneven in frequency response, and could not be coupled directly to telephone lines. In the acoustic phonograph, the recording artist spoke or played into a large acoustic recording horn, at the end of which was a recording stylus poised over a spinning disk of highly polished soft wax. The apparatus directly converted the sound energy into mechanical energy, which moved the stylus to trace a groove on the disk.

There seemed to be two likely paths to electrical recording. Either the phonograph could be engineered into a suitable device, or the sound could be translated into patterns recordable on photographic film. Western Electric did some work on the latter in 1913, but work began in earnest only after World War I. Assistant Chief Engineer E. B. Craft assigned a group under J. Maxfield to develop an electrical (or more properly, an electromagnetic) version of the acoustic disc phonograph, and a second under E. C. Wente, Irving Crandall, and Donald MacKenzie to investigate sound-on-film recording.

By mid-1922, Maxfield’s group had succeeded in producing an experimental prototype system for electrical disc recording, using Wente’s condenser microphone and amplifiers based on Arnold’s design. In the new system, a condenser microphone converted the musician’s sound energy intl electrical energy, which then underwent amplification before being converted into mechanical energy at the recording stylus. The stylus, as before, scratched a groove in a spinning wax disk. While the acoustic recording horn picked up only sounds aimed directly at it, the microphone was sensitive to more distant sounds. This allowed an orchestra to sit more normally, but it also meant that room acoustics and reverberations had to be studied and considered in equipment design.

E. B. Craft encouraged Maxfield to develop the system further for use in consumer phonographs. This required two years of additional work. In 1925, Maxfield and his group also re-engineered the phonograph, but it remained an acoustic-mechanical device, as the reproducer, now equipped with an acoustically designed horn, could fill an average household room with sound without using electrical amplification. The two major recording companies, Victor and Columbia, took licenses from Western Electric and switched to the new technology.

In the meantime, Crandall and Wente had succeeded in developing a prototype system for translating the electrical impulses from a microphone into variable-density light patterns on photographic film. Wente invented the light valve, a shutter of stretched metallic ribbon, to vary accurately the amount of light that reached and exposed moving film. in the light valve, the thin slit formed by a looped ribbon varied in width with the applied electrical current. A constant light source shown through the slit at moving photographic film, exposing a variable-density pattern on the film. After development, the film was played back between a constant light source and a photoelectric cell. The cell sent electrical signals analogous to the patterns of exposure on to an amplifier. Optical recording remained, in the view of the AT&T engineers of the mid-1920s, a more experimental system not ready for commercial exploitation.

—From IEEE Transactions on Education
Vol. 35, No. 4, November 1992



Biography of Edward Christopher Wente

Born Denver, Iowa 1889. Research physicist, Western Electric Company, 1914-25; Bell Telephone Laboratories, 1925-54. BA, Michigan, 1911; BS, MIT, 1914; Ph.D., Yale, 1918.

The first Progress Medal of the Society of Motion Picture Engineers was presented to Dr. Wente in 1935. The citation accompanying the award included these words by the president of the society: “…one man stood out above the others in the importance and volume of his contributions to the motion picture art… E. C. Wente.”

The needed removal of the power limitation in sound reproduction had come with the development of the hard vacuum tube in 1913. Still needed for good sound with motion pictures were high-quality transducers to convert from acoustic to electric energy, from electric to acoustic energy, and from electric energy to a permanent reproducing record. Wente provided the three needed transducers in the form of a condenser microphone, a moving coil horn type loudspeaker, and a variable density light valve for optical recording. He proceeded to work out the mathematical physics and then to develop suitable measuring instruments of great precision in the form of a measuring condenser microphone and a calibrating thermophone.

The sound motion picture was only one area of mass communication in which Wente’s ingenuity played a leading role in creating new multi-million-dollar industries. Other areas included the high-quality phonograph, radio broadcasting, the public address system, and the television sound equipment. His developments resulted in high quality, high power sound reproduction which was aesthetically and emotionally satisfactory to the ear. Previous quality, as for instance in the telephone, had been adequate for person-to-person communication, but never for mass audiences. His advances were later applied, turnabout, to the telephone transmitter and receiver with a great increase resulting in both quality and efficiency.

In addition, Dr. Wente made valuable contributions in the development of auditory perspective, the design of anechoic rooms, acoustic wall treatment, auditorium design, high-quality magnetic tape recording, automatically recording reverberation meter, transmission of pictures over telephone lines, electro-dynamic loudspeakers, a 100-element tone synthesizer, and, during World War II, to the development of the first electrical gun director and air raid warning sirens.

Dr. Wente has been granted thirty-six patents for his inventions, and has written a large number of significant papers on acoustics for the Physics Review, American Architect, Journal of Acoustics Society, Journal of the Society of Motion Picture Engineers, and other professional journals.

He is a Fellow of the American Physicists Society, the Society of Motion Picture and Television Engineers, the American Association for the Advancement of Science, and the Acoustic Society of America. He is a past president of the Acoustic Society (1942-43), was a member of its executive council (1933-36), and served on its editorial board for many years.

Other awards to Dr. Wente were the gold plaque of the Academy of Motion Picture Arts and Sciences, given jointly to him and Bell Telephone Labs in 1936 for the direction-controlled multi-cellular horn and the receiver unit demonstrated in auditory perspective; the Modern Pioneer Award presented by the National Association of Manufacturers in 1940 for outstanding inventions, in commemoration of the one hundred fiftieth anniversary of the founding of the U.S. Patent Office; the John Potts memorial medal of the Audio Engineering Society in 1957 and the John Price Wetherill Award of Franklin Institute in 1931 for his invention and development of the condenser microphone. Truly, “Modern acoustics may be said to have begun with the development of the condenser microphone by Wente,” as stated by Olson and Massa (Applied Acoustics, 2nd ed. p. 97).

Thanks to Dr. Sheldon Hochheiser for this information.