Gerhard M. Sessler

Gerhard M. Sessler
Gerhard M.
Electrical Engineering
Benjamin Franklin Medal
Darmstadt University of Technology | Darmstadt, Germany
With James E. West, for the invention and development of the first practical electret microphone, which can inexpensively be made small enough to fit into cellular phones, digital cameras, and other portable devices.

Gerhard Sessler and James West invented the most ubiquitous microphone in use today—the small, affordable, and high-performance foil electret microphone, which now serves as the basis of 90% of the more than 2 billion microphones produced annually. Working at Bell Labs in the 1960s, Sessler and West replaced the traditional microphone condenser—which was expensive, bulky, and demanded a high voltage input—with an "electret" foil. This foil, made of a piece of fluoroethylenepropylene, commonly known as Teflon, can permanently hold a charge independent from an electrical source. ("Electret" is a combination of the words "electric" and "magnet," since it can hold a permanent electric charge the way a magnet can hold a permanent magnetic charge.) Without the need for a big battery, a low-voltage, easily miniaturized, and inexpensive microphone was introduced, and has found its way into professional microphones, cell phones, hearing aids, baby monitors, video cameras, and more.

Gerhard Sessler grew up in Germany and earned his undergraduate degree in physics from the University of Gottingen in 1957. He stayed on at Gottingen to earn his Dr.rer.nat in 1959. His first job after graduation was at Bell Labs, where he worked until 1975, before returning to Germany to teach at Darmstadt University of Technology. Following the development of the electret microphone, Sessler continued to improve microphones, both with West at Bell Labs, and in Germany, where he invented what is known as the silicon microphone. This is a condenser microphone in which the sound-wave conversion membrane is etched directly onto silicon, allowing for numerous microphones to be embedded onto a single computer chip. It can be used for hearing implants, among other things. Sessler also continues to research and improve a wide variety of electret films.

Sessler holds over 100 patents and has received numerous awards for his work, including the Electrochemical Society's Callinan Award, AT&T's George R. Stibitz Award, the German Acoustical Society's Helmholtz Medal, the Acoustical Society of America's Helmholtz Rayleigh Interdisciplinary Silver Medal, the Eduard Rhein Foundation's Technology Award, and induction into the National Inventors Hall of Fame.

Information as of April 2010