Introduction|
Mono|
Dolby Stereo|
Dolby Surround|
Dolby Stereo
When we describe stereo today we refer to this 2 channel format. However, the first
stereo recordings were actually for movie theatres and contained 4 channels of audio
for surround sound. The 2 extra channels had to be dropped when the first stereo vinyl
records were made as this media did not have the storage capacity for all 4 channels.
As a result, hi-fi stereo as we know it is a 2 channel format.
Dolby Stereo is the movie theatre sound system using 4 channel audio and incorporating
Dolby Laboratories' noise reduction system to increase overall sound quality. Some
theatres still use Dolby stereo today, while the original 4 channel soundtrack has
been re-recorded on home media in the form of Dolby Surround.
Dolby Pro-Logic|
Dolby Pro-Logic II|
Dolby Digital|
Dolby Digital Surround-EX|
DTS|
DTS-ES|
THX|
Sony SDDS|
Stereo sound uses two separate audio channels.
The presentation is much improved when compared to a single mono soundtrack due
to the way stereo is heard by the human ear. Normal sounds that we hear are received
by each ear at a slightly different time. From this time delay we can work out in
which direction the sound is originating. Stereo uses this knowledge to create
a 'soundstage' between 2 speakers. By adding a slight time delay for each speaker
channel, a single sound recording can trick the ear into thinking that the sound
is comming from the left or from the right of centre. The effect can separate
individual instruments on a CD recording making the whole presentation more realistic
and involving.
