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Gerhard Sessler: The Other Half of the Electret, and Then MEMS

By Infinite Creation · Profile

Patent drawing from the work of Gerhard Sessler.

At a Glance

Gerhard M. Sessler (born 1931) co-invented the electret condenser microphone with James West at Bell Labs in the early 1960s, and later contributed to the development of the silicon MEMS microphone. Between them those two devices account for essentially every microphone in consumer electronics.

Born 1931, Germany, worked in the United States and Germany
Anchor year: 1962, the electret condenser microphone
Strand: overlooked

Career

The problem as it stood

Same as for West: condenser microphones were excellent and required a polarising supply, which ruled them out of anything small, cheap or battery-powered.

What he actually did

Sessler and West developed the electret transducer together, and Sessler continued working on electroacoustic transducers for decades afterwards at the Technical University of Darmstadt, including on silicon micromachined microphones.

How it worked

The electret supplies its own bias. The MEMS successor takes the same principle into semiconductor fabrication: the diaphragm and backplate are etched from silicon, so the microphone becomes a chip that can be placed by the same machines that place every other component.

What it made possible

The electret put microphones into telephones and consumer audio. MEMS put several into every smartphone, enabling beamforming, noise cancellation and always-listening voice assistants. The second step is what made microphone arrays economically ordinary.

What happened to him

He returned to Germany as a professor at Darmstadt, publishing extensively on electroacoustics, and has received major awards jointly with West.

Where the credit landed

Sessler has a separate page from West because the contributions are separable: he continued into the MEMS generation that West did not, and that second step is what made microphone arrays ubiquitous. Splitting genuinely joint inventors into one page each is the corpus's rule only where their work diverges afterwards. Where it does not, the pair share a page.

Known For

The electret and MEMS generations between them cover nearly all consumer microphones.
MEMS turned the microphone into a placeable chip, which is why phones have several.
Microphone arrays and beamforming are downstream of MEMS economics.

Knowledge Base

What You'll Learn

Two transducer generations, one operating principle, sixty years apart.

Why several microphones are better than one

With two or more microphones a fixed distance apart, sound from different directions arrives at slightly different times. Combining the signals with matched delays reinforces one direction and cancels others, beamforming, in software, with no moving parts. That is how a phone isolates your voice from a noisy street, and it only became practical once a microphone cost pennies and occupied a few cubic millimetres.

Where This Fits

The electret and MEMS microphones are the capture link in most modern devices, the start of the chain covered in A History of Broadcast Technology.

FAQ

Q: What is a MEMS microphone?
A: A microphone whose diaphragm and backplate are micromachined from silicon, making it a surface-mount component. It works on the same capacitive principle as the electret but is manufactured like a chip.

Q: Why do phones have more than one microphone?
A: To beamform, combining several signals with matched delays isolates sound from a chosen direction and cancels the rest, which is how voice is separated from background noise.

Vocabulary

Electret. A material holding a permanent electrical charge, in the way a magnet holds a magnetic field. Removes the need for an external polarising voltage, which is what made small condenser microphones practical.

MEMS. Micro-electro-mechanical systems, mechanical structures built at the scale of semiconductor chips. Allows a working microphone to be manufactured by the same process as an integrated circuit.

Transducer. Any device converting one form of energy into another. A microphone converts sound pressure into electrical signal, and its design determines how faithfully that conversion happens.

Polarising voltage. The charge held across a condenser microphone's capsule, needed for it to work at all. Supplied externally in traditional designs and held permanently in the material in an electret.

Sources

The electret patent was checked against the record. Checked 20 August 2026.

US Patent 3,118,022, Electroacoustic Transducer. Filed 22 May 1962 and granted 14 January 1964, assigned to Bell Telephone Laboratories and naming Gerhard M. Sessler and James E. West together. The specification describes a prepolarised electret diaphragm that removes the need for any externally applied direct current bias.