At Bell Labs in the late 1950s, Flanagan continued to research formant-based vocoders. His first technical assistant was Bernie Watson—a name that couldn't help appealing to Flanagan's puckish sense of humor.

"He often found a reason to say, 'Mr. Watson, come here, I want to see you,' " says David.

After just three years, Flanagan was made a department head (although throughout his career he has spent about 50 percent of his time doing his own research). He and his team worked on an artificial larynx, eventually getting more than 30 000 of the devices out to people who needed them.

In the 1960s, digital computers began changing how research was done, and speech research was no exception. Flanagan and his group started using an IBM 650 mainframe computer, intending to simulate a telephone transmission system that would enable them to test future advances without building hardware. That sounds commonplace today, but when Flanagan began this work, such simple components as analog-to-digital (A-to-D) converters did not exist. There was no way to get real-time analog signals into a digital computer.

Instead, Flanagan and his group would use a photograph of an oscillogram and measure the various amplitudes of the signal. Those numbers were then recorded on punch cards—with a huge stack representing a few seconds of speech—and fed into the computer. The output would be a plot of processed waveforms.

This direction of research, Flanagan says, excitement in his vibrant blue eyes, "opened up the field of signal processing, which had not even existed before 1965 or thereabouts—and now it's an IEEE society," the IEEE Signal Processing Society.

Making these physical measurements of waveforms to feed into the computer gave Flanagan other ideas. Instead of measuring the waveforms as generated by an oscilloscope, why not measure the motion of the vocal cords themselves? Working with high-speed motion pictures taken of the vocal cords via a dental mirror, he measured the vibration and area of those cords and used these data to compute spectral characteristics of the vocal source.

The analysis supported new computer simulations of the interaction between vocal cords and vocal tracts, using physiological factors to form natural speech synthesis, an early example of what we now call model-based coding. "People don't use this [type of simulation] as a basis for a voice synthesizer yet," he says, but he thinks they eventually will. "It's a frontier challenge."

By the 1970s, Flanagan was still working on efficient transmission of speech, but now it was in a digital world. Again, he turned conventional methodologies upside down—or at least sideways. Speech was being sent digitally through the telephone transmission system by a method called pulse-code modulation, or PCM. A PCM encoder samples signals at regular intervals and represents the various amplitudes with binary numbers. Flanagan developed a version of PCM that, instead of recording the amplitudes themselves, encodes differences between successive samples for transmission or storage, adapting the algorithm depending on characteristics of the input signal.

This adaptive differential PCM immediately doubled the efficiency of conventional digital telephone transmission. It enabled digital telephone channels that had required 64 kilobits per second of bandwidth to run at 32 kb/s. A further advance in this direction—coding in sub-bands—reduced the rate to 16 kb/s and led to the first Audix voice mail system, a product that eventually became a huge business for AT and T. Along the way to that success, Flanagan was awarded an early patent for packet transmission of speech, one form of which we now call voice over IP (though the patent expired long before the technology was commercialized).

In the 1980s, the research team was working on efficient speech coding for cellphones. Lawrence Rabiner, now a professor of electrical and computer engineering at Rutgers University, New Brunswick, N.J., and the University of California at Santa Barbara, was then a Bell Labs researcher under Flanagan. He recalls that Flanagan immediately began asking how music could be coded in a similarly efficient way. He assigned researchers to work on the challenge, and members of that team later developed the ubiquitous MPEG-1 Layer 3 audio coding format, known as MP3.

"Every time we solved one challenge, he was way ahead of us with the next challenge," says Rabiner. "He felt that his job was to produce a steady stream of out-of-the-box thinking."

Flanagan climbed steadily up the ranks at Bell Labs, eventually becoming director of the Information Principles Research Laboratory. But while taking on management functions, he always continued his own work [see photo, "In the Lab"]. "I liked the fact that you could influence the directions of work you considered important," he says with a hint of a Mississippi drawl, "but I've always tried to balance my own work interests with facilitating what other people are doing."

Among his other projects, he pushed ahead with work in automatic speech recognition, even though it didn't have much support from higher-ups. Eventually, he used a Data General Nova 16-bit minicomputer to build a telephone reservation system for air travel.

"The ultimate fruit of that didn't come until 1992," Cox told IEEE Spectrum, "when Voice Recognition Call Processing was put into the telephone network. Jim had promised that there would be tangible results and persisted in spite of the skepticism and resistance he met. And it paid off hugely for AT and T."

In his spare time, Flanagan helped his brother, also an electrical engineer, run the cotton farm and a cattle ranch back in Mississippi. Balancing his two worlds, he had the ideal career, Flanagan says, except for six months in 1973.