History of multi-channel sound (surround sound)
Home theatre, or surround sound (home cinema) as it is also known, has its origin in systems developed for public cinemas, many years ago.
Mono and Dolby Stereo
At first all films were recorded in mono, with one speaker placed directly behind the silver screen. This is actually a very good solution, as everyone in the cinema hears the sound coming from the same speaker(s). As technology improved and music was starting be recorded in stereo (two channels) rather than one (mono), so were soundtracks. The main problem with film sound was that it was really very bad, as the sound was coming off a magnetic tape stuck onto the film reel that deteriorated very fast and left almost nothing butt tape hiss. A company specializing in hiss or noise reduction, Dolby Laboratories was called in to help improve the sound of the film soundtrack by reducing the tape hiss. This became known as Dolby Stereo. The only problem with stereo film sound is the placement of speakers. The speakers were moved from dead centre behind the screen, to left and right on either side of the screen.
From Dolby Stereo to Dolby Surround
Soon it was discovered that sound could be manipulated with basic processors, to extract information form the stereo soundtrack to create a more realistic ambience by playing the extracted information through speakers placed around the listeners. This also had the effect that the room was more evenly filled with sound and the "reverb" or ambient sound was coming from the back and sides of the room just like it did during the recording. As Dolby was already extensively involved with the processing of sound, they further developed this early surround sound and thus it became known as Dolby Surround.