Stereo Listening - Acoustics, Electroacoustics, And Pychoacoustics

Our experience of sound is necessarily subjective, but knowing the history of the science of stereophonic sound can help us to make intelligent decisions about our listening spaces and equipment.

- Richard Honeycutt

The first method for recording sound was Léon Scott’s phonautograph, developed in 1857. It provided a visible trace of sound waves, but did not provide a way to play back sounds. A way to retrieve sound from a recording was suggested by French inventor Charles Cros, and demonstrated independently by American inventor Thomas Edison in 1877. The gradual move from acousto-mechanical to electrical recording/ playback proceeded throughout the early 20th century, but always with only one channel of sound. Even though fidelity improved with these advances, no spatial information was available to the listener.

French inventor Clément Ader demonstrated a two-channel audio system in Paris in 1881, using telephone transmitters connected from the stage of the Paris Opera feeding pairs of telephone receivers through which listeners could experience something very like what we today call binaural reproduction. This process was commercialized in France and England from 1890 to 1932, but it was used for live performances only—sound recording and reproduction were not involved.

British engineer Alan Blumlein invented and patented stereo recording and playback in the early 1930s, with the first stereo discs being cut in 1933. A recording of Mozart’s Jupiter Symphony was released in 1935, the same year that the first stereophonic motion picture sound was demonstrated.

Meanwhile, in the US, Harvey Fletcher of Bell Telephone Laboratories (BTL) was experimenting with a “maximalist” approach to providing realistic spatial information for electrically transmitted audio. Fletcher used up to 80 microphones to pick up the sound of an orchestra, with the signals being transmitted via equalized telephone lines to the same number of amplifiers and speakers. The speakers were spatially distributed in the listening room to match the microphone positions in the recording room.