An estimated eight percent of Americans suffer from impaired hearing and feel somewhat shut out of theaters, churches—the whole public arena. But now, in a promising breakthrough, the hard of hearing can take a seat at a Broadway musical and never miss a beat. A device converts the words and music into invisible infrared light which is then beamed to headphone receivers with diode lenses that reconvert the rays to audible sounds. The ears-on-the-aisle, individually controlled to amplify up to 101 decibels (a jet takeoff registers 120 at 100 feet), have worked for theatergoers with as much as 75 percent hearing loss. The system is adaptable for everything from home TV sets and stereo systems to auditorium public-address systems.

The designer is Richard Fitzgerald, 39, a New York audio expert, who adapted a technology developed by West Germany's Sennheiser Electronic Corp. While installing the sound equipment for the Broadway revival of Peter Pan last fall, he decided to add the Sennheiser system. It required six briefcase-sized transmitters connected to the master sound system at the Lunt-Fontanne Theatre. Because the transmission is by light rather than sound or radio waves, it is free of distortion from noisy audiences, poor acoustics or nearby CB radio calls. "The transmitter is like an antenna on a radio station; it takes in sound and simply changes the frequencies," explains Fitzgerald. "When the body is miked, as is the case with Sandy Duncan in Peter Pan, we've in effect put ears right on her body."

Off Broadway, Fitzgerald lives in suburban Yonkers with his schoolteacher wife, Elizabeth, 39, and daughters Shannon, 13, and Raissa, 11. Now president of the Sound Associates audio firm founded by his father in 1948, he is testing the utility of infrared for a portable simultaneous translation system. The one place infrared would be unusable is in sunlight, where the natural light rays "drown out" the beam.

It costs $13,000 to add an infrared system in a typical Broadway theater, and each battery-powered headset runs $115. There are federal funds set aside for providing the arts to the handicapped that could subsidize installation in U.S. theaters and concert halls. As one happy 10-year-old exulted after a performance of Peter Pan: "I almost forgot I couldn't hear."