Gerhard M. Sessler

Gerhard M. Sessler (*1931)

Gerhard M. Sessler. Image: TU Darmstadt archives
Gerhard M. Sessler. Image: TU Darmstadt archives

Gerhard M. Sessler was professor at the TU Darmstadt Department for Electrical Engineering and Information Technology from 1975 until 1999.

In the 1960s, he worked for Bell Laboratories in the US and led the Electro-Acoustics Research Group from 1967. In 1962, he invented the electret condenser microphone together with Dr. James Edward West – a milestone in technical acoustics. Today, more than two billion of these microphones are sold worldwide for telephones, video cameras, hearing aids, toys, as well as radio and television recordings every year – this means a market share of over 80 percent.

The electret microphone features a metal-coated membrane, or a layer of fluorocarbon polymers on the backplate electrode, carrying a permanent electric charge that is particularly stable and will last for decades. The charge replaces the electrical bias that was needed in condenser microphones and simplifies the microphone circuitry substantially.

Gerhard Sessler has worked on many fields of technical acoustics, research on electro-active materials and the digital processing of acoustical signals. In 1983, he developed the sub-miniature silicon condenser microphone at TH Darmstadt together with Dietmar Hohm. This technology makes it possible to produce thousands of minuscule microphones on a single silicon wafer and is now in use in mobile phones and other devices.

In 1999, Sessler and West were included in the US “National Inventors Hall of Fame”. In 2010, both received the Benjamin Franklin Medal in the US, an honour previously accorded to heavyweights like Thomas A. Edison, Niels Bohr, Max Planck, Orville Wright, Albert Einstein and Stephen Hawking.