Dolby™ Digital 5.1

Dolby Digital produces 5 discrete (perfectly separated) sound channels and a dedicated LFE (Low Frequency Effects) subwoofer channel.
For this reason it is known as a 5.1 channel system (the .1 indicating the subwoofer channel that has limited frequency for just the low audio frequencies)
Dolby Digital has all the benefits of an all digital system in terms of clear sound without distortion and noise. Compared to Dolby Pro Logic, the sonic improvement almost corresponds to stepping up from cassette tape to CD
Dolby Digital is used in a variety of video/audio formats world wide including. DVD, Laserdisc, Computer Games, Radio and TV broadcasting.
Dolby Digital was originally known as AC-3, this is still the name of the encoding used.