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James L. Flanagan, center, with fellow Bell Laboratories scientists in 1970. Mr. Flanagan published a prescient article while at Bell Labs that foretold several technological advances.Credit Alcatel-Lucent/Bell Labs

James L. Flanagan, whom we can thank for articulate digital assistants like Siri and intelligible subway loudspeakers and blame for the disembodied voices that inform frustrated telephone callers to listen carefully because their bank’s, airline’s or insurance company’s automated customer care options have changed, died on Tuesday at his home in Warren Township, N.J. He was 89 and would have turned 90 the next day.

The cause was heart failure, his wife, Mildred, said.

As a leading researcher at AT&T Bell Laboratories, Dr. Flanagan was a pioneer in the field of acoustics, envisioning and providing the technical foundation for speech recognition, teleconferencing, MP3 music files and the more efficient digital transmission of human conversation — most famously in a 1976 article, “Computers That Talk and Listen: Man-Machine Communication by Voice,” that appeared in Proceedings of the I.E.E.E., a journal published by the Institute of Electrical and Electronics Engineers.

“What is so significant about this article is that it painted a picture of society in the 21st century in a paper published 39 years ago,” Lawrence R. Rabiner, a friend and former colleague who teaches electrical and computer engineering at both Rutgers and the University of California, Santa Barbara, said in an interview. “How much more vision could anyone have at that time?”

Dr. Flanagan was granted or shared in about 50 patents, including an artificial human larynx and a typewriter activated by the same audio tones as a push-button phone that allowed deaf people to communicate remotely.

His innovations included preserving the sound of a human voice while crunching it digitally, as well as teaching computers to articulate — converting sound waves into digital pulses. He also helped devise a “force-feedback” tactile glove, similar to today’s video game accessories, that enabled medical students to simulate hands-on examinations when a live patient or cadaver was not available (or to mimic a game of handball).

Dr. Flanagan also played a minor role in the drama surrounding the downfall of President Richard M. Nixon.

In 1974, Dr. Flanagan was one of six acoustical experts appointed by Chief Judge John J. Sirica of the United States District Court in Washington who concluded that 18 1/2 minutes of a conversation between Nixon and his chief of staff, H. R. Haldeman, on June 20, 1972, had been deleted as a result of at least five separate erasures and re-recordings requiring “hand operation of keyboard controls.” The conversation took place three days after the break-in at Democratic National Committee headquarters in the Watergate hotel and office complex in Washington.

Nixon’s personal secretary, Rose Mary Woods, accepted blame for erasing the first five minutes of the tape, saying she had been interrupted by a telephone call while transcribing it. But her explanation was generally dismissed as technically implausible. Nixon later resigned under threat of impeachment for, among other charges, withholding evidence.

James Loton Flanagan was born on his family’s cotton farm in Greenwood, Miss., at the edge of the Mississippi Delta, on Aug. 26, 1925, to Hanks Flanagan, a farmer, and the former Wilhelmina Barnes.

Infused from an early age with a passion for science and mathematics, he joined the Army Air Forces at 17, worked to perfect signal scrambling and radar during World War II and returned to Mississippi State University, where he graduated with a bachelor’s degree in electrical engineering in 1948.

He received a master’s degree and a doctorate from M.I.T., and in 1956 he joined Bell Labs, where he would work for 33 years. He retired in 1990 as director of information principles research.

He was subsequently a professor and vice president for research at Rutgers, where he remained until his retirement in 2005.

In addition to his wife, the former Mildred Bell, he is survived by three sons, Stephen, James and Aubrey; a brother, Thomas; and five grandchildren.

In his 1976 article, Dr. Flanagan recalled that digital speech recognition was originally developed by the telephone company to verify the identity of callers and deter credit card fraud.

Prospects, he predicted, were bright for the technology’s application to other transactions, like making department store purchases and checking bank balances. People might be able to dictate notes that would appear as text or even speak the name of someone they wanted their phone to dial automatically.

“As always,” he wrote, suggesting that imagination was in shorter supply than technical potential, “there are fewer people who know what to do, rather than how to do it.”