Stereophonic sound

Time difference in a stereophonic recording of a car going past

Stereophonic sound or, more commonly, stereo, is a method of sound reproduction that creates an illusion of multi-directional audible perspective. This is usually achieved by using two or more independent audio channels through a configuration of two or more loudspeakers (or stereo headphones) in such a way as to create the impression of sound heard from various directions, as in natural hearing. Thus the term "stereophonic" applies to so-called "quadraphonic" and "surround-sound" systems as well as the more common two-channel, two-speaker systems. Stereo sound has been in common use since the 1970s in entertainment media such as broadcast radio, TV, recorded music, internet, computer audio, and cinema.

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How stereophonic sound systems work. The main diagram shows a simplified situation in nature. The inset shows the electronic simulation. Notably, such electronic systems require more than one speaker.