There are many surround systems available in the market .They use different technologies for produce surround effect. Some Surround sound is based on using audio compression technology (for example Dolby ProLogic? or Digital AC-3?) to encode and deliver a multi-channel soundtrack, and audio decompression technology to decode the soundtrack for delivery on a surround sound 5-speaker setup. Additionally, virtual surround sound systems use 3D audio technology to create the illusion of five speakers emanating from a regular set of stereo speakers, therefore enabling a surround sound listening experience without the need for a five speaker setup.
We are now entering the Third Age of reproduced sound. The monophonic era was the First Age, which lasted from the Edison's invention of the phonograph in 1877 until the 1950s. during those times, the goal was simply to reproduce the timbre of the original sound. No attempts were made to reproduce directional properties or spatial realism.
The stereo era was the Second Age. It was based on the inventions from the 1930s, reached the public in the mid-'50s, and has provided great listening pleasure for four decades. Stereo improved the reproduction of timbre and added two dimensions of space: the left - right spread of performers across a stage and a set of acoustic cues that allow listeners to perceive a front-to-back dimension.
In two-channel stereo, this realism is based on fragile sonic cues. In most ordinary two-speaker stereo systems, these subtle cues can easily be lost, causing the playback to sound flat and uninvolved. Multichannel surround systems, on the other hand, can provide this involving presence in a way that is robust, reliable and consistent.
The purpose of this seminars is to explore the advances and technologies of surround sound in the consumer market.
Human hearing is binaural (based on two ears), yet we have the ability to locate sound spatially. That is, we can determine where a sound is coming from, and in most cases, from how far away. In addition, humans can distinguish multiple sound sources in relation to the surrounding environment. This is possible because our brains can determine the location of each sound in the three-dimensional environment we live in by processing the information received by our two ears.
The principal localization cues used in binaural human hearings are Interaural Intensity Difference ( IID ) and Interaural Time Difference ( ITD ). IID refers to the fact that if a sound is closer to one ear than the other, its intensity at that ear is greater than at the other ear, which is not only farther away but also receives the sound shadowed by the listener's head. ITD is related to the fact that unless the sound is located at exactly the same distance from both ears (i.e. directly in front or back of the listener), it arrives at one ear sooner than the other. If the sound reaches the right ear first, the source is somewhere to the right, and vice-versa. By combining these two cues and other related to the reflection of the sound as they travel to our eardrums, our brains are able to determine the position of an individual sound source.
The principal format for digital discrete surround is the "5.1 channel" system. The 5.1 name stands for five channels (see figure 1 below) (in front: left, right and centre, and behind: left surround and right surround)of full bandwidth audio (20 Hz to 20 kHz) plus a sixth channel which will, at times, contain additional bass information to maximize the impact of scenes such as explosions, etc.