An audio recording can be played in many ways. The simplest method and the one that was used in the first soundtracks is called MONO. This means that all sounds are recorded on a single audio channel and are usually played back with only one speaker.
2-channel recordings, which play the sound through 2 speakers on one side and the other on a listener, are often called STEREO.
Introduction to Surround Sound
There can be no equivalence between stereo and stereophonic since the latter refers to a larger series of multi-channel recordings. Double-channel sound has become standard in FM radio broadcasts and most TV broadcasts, as well as home audio equipment. The simplest stereo recordings are made using a microphone that records the sound that comes in two directions, like the two ears of a man.
Surround sounds bring the idea of music a little further, bringing more audio channels, so the sound starts from several directions. The term “surround sound” from the multichannel sound systems developed by Dolby Laboratories is more used as a generic term for cinema sound systems and home cinemas.
The Use of Microphones
Recording surround sounds are usually made by using multiple microphones in different directions. Most of the time, the soundtrack of a movie is processed in the studios of sound technicians who choose the sounds to insert on each channel, some even record at that film scene, others are processed, or create directly on Computer, Music backgrounds or other special effects.
Different Technologies That Create Surround Sound
The latest in digital surround sound technology comes from Sony and has been called Sony Dynamic Digital Sound® (SDDS). This brings five audio channels in front, two surround sound channels (one left and one right) plus another LFE (Low-Frequency Effects) channel reproduced by a subwoofer.
Like Dolby Digital, the SDDS system encodes digital information using a distinct pattern of dark and bright areas on the film. In this case, the reader contains a laser on one side of the movie and a matrix of photosensitive cells on the other. The laser light passes through the transparent parts of the film but not through the opaque ones. The photosensitive cells on the other side that are not exposed to light allow them to pass through a weak current through them, while those exposed to light do not let them. In this way, the sound processor receives the digital model and then transforms it into an audio signal. Unlike other systems in digital format, SDDS uses two identical tracks to make error correction.
Dolby and DTS – Working Together
Electronic equipment manufacturers used Dolby and DTS systems to create home-cinema versions. Even for SDDS, there is a 7 + 1 surround system (7 audio channels + one for the subwoofer). Since digital audio can not be recorded on video tapes and can not be emitted by conventional cable television, the only mode of transmission is DVD, satellite or digital cable. You can find out how they work by reading the article about home-cinema systems.
For movie and music fans everywhere, surround sound has become an integral part of a cinematic experience and for producers, sound fitting is a major component of the production process. The surround sound pushed the movie into a new dimension, bringing the audience straight into the middle of the action. But for the 3D effect to be even more realistic, it took the help of optics. 3D movies use specially filmed and processed pictures, combined with special glasses that spectators receive at the entrance to the cinema. The optically generated effect, coupled with the surround sound effect, makes the film a competitor very hard to beat by any current home theater system.
A standard 5.1 speaker system may be enough to create the surround system in a regular room, but when it comes to larger rooms and amphitheaters one will need to look into the usage of 7.1 and 7.2 speaker setups.