surround

Surround sound is a technique for enriching the fidelity and depth of sound reproduction by using multiple audio channels from speakers that surround the listener (surround channels). Its first application was in movie theaters. Prior to surround sound, theater sound systems commonly had three "screen channels" of sound, from loudspeakers located in front of the audience at the left, center, and right. Surround sound adds one or more channels from loudspeakers behind the listener, able to create the sensation of sound coming from any horizontal direction 360° around the listener. Surround sound formats vary in reproduction and recording methods along with the number and positioning of additional channels. The most common surround sound specification, the ITU's 5.1 standard, calls for 6 speakers: Center (C) in front of the listener, Left (L) and Right (R) at angles of 60° on either side of the center, and Left Surround (LS) and Right Surround (RS) at angles of 100–120°, plus a subwoofer whose position is not critical.
Surround sound typically has a listener location or sweet spot where the audio effects work best, and presents a fixed or forward perspective of the sound field to the listener at this location. The technique enhances the perception of sound spatialization by exploiting sound localization; a listener's ability to identify the location or origin of a detected sound in direction and distance. This is achieved by using multiple discrete audio channels routed to an array of loudspeakers.

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