In December 1931, Alan Dower Blumlein, a British electrical engineer working for the music recording and publishing company Electrical and Music Industries (EMI), filed a patent for a two-channel audio system. Until then, audio had been recorded and played back through a single, fixed channel. Blumlein called his invention binaural sound, but today we call it stereo.
On 2 April of this year, this breakthrough in sound recording was recognized with an IEEE Milestone. Administered by the IEEE History Center, the Milestone program recognizes outstanding technical developments from around the world.
The Milestone plaque was unveiled at London’s iconic Abbey Road Studios, where Blumlein worked from time to time during the 1930s, when the studio was called EMI Studios. (Its name was changed in 1970 after the Beatles released their famous Abbey Road album, named after the street on which the studio is located.)
While this might be Blumlein’s best-known contribution, he also made several pioneering inventions in telecommunications and television.
LIFE IN STEREO
Blumlein had his epiphany about stereo in early 1931 while watching a movie with his wife. He became increasingly frustrated at hearing actors’ voices coming from the same fixed speaker as they moved around. Blumlein thought this to be unrealistic and confusing, and soon he invented a way to make the sound follow the actor across the screen.
His patent for binaural sound contained 70 unique claims. A shuffling circuit would process the sound recording of a film to preserve the direction of the sound. Two microphones, recording separately, would be positioned at right angles to each other to capture the full stereophonic sound of the actors’ voices. These became known as the Blumlein pair. Additionally, for phonograph records, two channels would be recorded in a single groove of a record so the recordings could be played back through a single loudspeaker.
In 1933, Blumlein began his binaural experiments for both film sound and photograph recordings. Later that year he cut the first stereo records and produced several promotional films to demonstrate his technology. In the film Walking and Talking, recorded at EMI Studios, Blumlein and his colleagues repeatedly walked and talked back and forth around the studio, which showed that by using stereo, sound appeared to come from wherever the speaker was standing. For another, Trains at Hayes Station, Blumlein took his stereo technology outside to a train station just outside central London and filmed trains moving across the screen.
The lack of commercial interest prompted EMI to shelve the research. A stereo system for phonograph records cost roughly twice as much as a monophonic system, and at the time it was not clear whether consumers would think the sound was so much better as to be worth twice the price.
Bell Laboratories was also experimenting with binaural sound at around the same time. In the late 1930s and early 1940s, it worked with Universal studios, Walt Disney, and MGM to produce soundtracks for movies. Stereo sound for movies finally garnered public interest on 30 September 1952 with the release of This Is Cinerama, a demonstration film, at the Broadway Theater in New York City.
After his stereo experiments in the early 1930s, Blumlein turned his attention to other matters. He worked on the high-definition electronic TV system that EMI unveiled in 1936. Blumlein focused on the electronic cameras that captured video signals outdoors, just in time to broadcast King George VI’s coronation procession in May 1937.
During the war, Blumlein played a key role in developing airborne interception radar. He incorporated a binaural system into aircraft sound detectors using a cathode ray tube. However, his life was cut short on 7 June 1942 when the Halifax bomber in which he was testing the H2S, a ground-scanning radar system, crashed, killing everyone on board. He was 38.
The British authorities kept Blumlein’s death a secret to cover up the setback in the radar project. Using his circuit designs, the British Air Ministry managed to complete H2S. This technology made possible for the first time accurate bombings of ground targets at night and in poor weather.
An obituary was never published. “Blumlein’s radar work was top secret,” says Anthony Davies, professor emeritus in the electronic engineering department at King’s College, in London, and former IEEE Region 8 director. “After the war I think people just forgot about him.”
Davies noted at the milestone ceremony that many modern technologies can be traced back to Blumlein. “Recording studios still use the Blumlein pair, and we still record vinyl records in the way he suggested,” Davies says. “His loading coil—an inductor that is inserted into an electronic circuit to increase its inductance— were used until the end of the analog telephone era. If you look inside today’s mobile phones, you’ll see circuit structures that are directly descended from Blumlein’s ideas. He was an incredible person, unequaled as a circuit designer.”
On 12 February 2017 Blumlein posthumously received a Grammy award from The Recording Academy.*
*This article has been updated.