surround sound 
A system for recording and reproducing sound that involves three or more channels and speakers. Such a system creates an environment in which the speaker is effectively surrounded by sound sources. In addition to being used in movie theaters, this type of arrangement is now available in the home. Surround-sound systems are available in digital and analog versions. Digital surround sound uses the 5.1 format to record sound. Dolby Pro Logic technology is used for analog surround sound.