Iconic Microphone Is Named an IEEE Milestone

The Shure Unidyne mic has been the standard since 1939

21 May 2014

It was the microphone of choice for Frank Sinatra and Elvis Presley, and has been used by politicians around the world, including every U.S. president since Lyndon B. Johnson. The Unidyne microphone, developed by Shure, in Niles, Ill., has been named an IEEE Milestone in Electrical Engineering and Computing

Administered by the IEEE History Center, the Milestone program recognizes outstanding technical developments from around the world.

The Unidyne debuted in 1939 as the world’s first single-element dynamic microphone to offer unidirectionality, and it has been a mainstay in the audio world ever since. (A unidirectional microphone is more sensitive to sound coming from the front, and hence relatively unaffected by noise coming from other directions).


Benjamin Bauer was a 25-year-old transducer development engineer at Shure Brothers Co. (now known as Shure Inc.)* and a recent graduate of the University of Cincinnati when he developed the Uniphase acoustical system, the technology that made possible the first Unidyne microphone. 

The first series of Unidyne mics featured a signature chrome-plated die-cast casing and a cardioid pattern that helped reduce unwanted background noise. The 55S featured a slimmer design than the original. Photo: Shure Inc.

Bauer’s system uses a single dynamic mic element, in which a voice coil is attached to a lightweight diaphragm. The voice coil sits within the field of a permanent magnet. The diaphragm and the voice coil are moved by sound waves, and an analogous electrical signal is produced within the voice coil wire. This technology reduced the size, weight, and cost as well as improved the performance of the company’s earlier microphones.

The first series of Unidyne mics, known as the 55 Series, featured a chrome-plated die-cast casing and a cardioid pattern that helped reduce unwanted background noise, which were brand-new features for a microphone, as well as a frequency response tailored to human speech.

Shortly after their introduction, the 55 Series microphones caught on with entertainers, musicians, and politicians worldwide. They were prominently featured in live performances by Duke Ellington and the aforementioned Sinatra and Presley.

Bauer was named an IEEE Fellow in 1952 for “important contributions to the development of microphone and other audio devices.”


Another Shure engineer, Ernie Seeler, improved the microphone in 1959 by developing a smaller and more durable version, the Unidyne III. Because of its sturdy construction, which included a screen to reduce wind noise and its ability to work well with instruments that produce high sound-pressure levels like snare drums and electric guitars, it is now the industry standard for rock concerts and outdoor festivals.

Today, U.S. President Barack Obama speaks into a Unidyne III when addressing the public. And just last year, the microphone captured live TV interviews with the crew aboard the International Space Station. 

A ceremony for the Milestone was held on 31 January with a plaque mounted on a wall in Shure’s lobby. The plaque reads:

In 1939, Shure Incorporated introduced the Unidyne microphone. Using the Uniphase acoustical system, the patented Unidyne was the first microphone to provide directional characteristics using a single dynamic element. This breakthrough offered lower cost, greater reliability, and improved performance for communication and public address systems. Shure Unidyne microphones are still manufactured and used worldwide in numerous audio applications.

This article was written with assistance from the IEEE History Center, which is funded by donations to the IEEE Foundation.

*This article was corrected from a previous version.

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