stereo

Stereo, short for stereophonic sound, is a method of sound reproduction that uses two or more separate audio channels to create the impression of directional sound sources around the listener.

In two-channel stereo, the left and right channels carry different signals. By adjusting levels, timing, and phase between channels, engineers simulate the location of sounds in space. The brain combines the two input streams to estimate direction, distance, and width. Room acoustics and playback equipment influence the resulting image.

The idea traces to the 19th century with the stereoscope; in the realm of sound, early experiments date to the 1930s and 1950s, and commercial stereo records and broadcasting popularized the format in the late 1950s.

Two-channel stereo is standard for music, films, and broadcasts. It is delivered via loudspeakers, headphones, or car audio, and encoded on media such as vinyl records, magnetic tapes, compact discs, or streaming.

Although stereo cannot reproduce all spatial cues of a real three-dimensional sound field, it remains widely used due to simplicity and compatibility. It coexists with surround formats that add more channels to create more immersive spatial experiences.