The original multi-channel movie surround sound format, still widely used for home cinema in the form of Dolby Surround.
INTRODUCTION
MONO
STEREO
QUAD
DOLBY STEREO
DOLBY SURROUND
DOLBY PRO-LOGIC
DOLBY DIGITAL
DOLBY DIGITAL-EX
DTS
DTS-ES
MPEG-II
SONY SDDS
THX
TIMELINE

Sound Formats

 

Dolby Stereo  
   

DOLBY STEREO

Dolby Stereo was created by Dolby Laboratories in 1976 as a multi-channel sound system for use in the cinema, and is based on the original stereo theatre sound that dates back to the 1930's. New technology allowed two additional 'hidden' audio channels to be included within the existing two channels of stereo sound. These extra channels contained information for a speaker placed centrally behind the cinema screen, and for multiple surround speakers placed on the side and rear walls of the theater. A special decoder was used to read and separate the four channels. The principal was to create a more realistic and involving atmosphere when watching movies at the cinema. The theory of multi-channel cinema sound was well established, but Dolby added more advanced encoding / decoding techniques and noise reduction. The main selling point of Dolby Stereo was that it could be encoded on the actual movie filmstrip as a two channel optical track that could fit in the same space previously occupies by optical mono sound.

Dolby Stereo has evolved into Dolby Surround and Dolby Digital, and it is this format that made home cinema possible.