.: A peep into the world of multiple-channel "surround sound" format

With mainstream consumer audio technologies having under gone a sea change over time, music enthusiast are confronted with confusing terminologies, catch-phrases, buzzwords and comparisons that are taken out of context. A look at the back of the DVD case will unveil a number of different logos denoting different surround sound formats that often leave end users baffled.

This tutorial outlines the various multi-channel sound formats used by the industry so that an avid listener will have a better idea of what it's all about—and what is needed to experience the added sound depth.

What is Surround Sound?

The idea behind Surround Sound is to create a three-dimensional sound field during audio playback using multi-channels of sound so as to simulate a more realistic audio ambience for excellent real-life auditory experience to the listeners. This concept is actively implemented in cinema sound systems, technical theatre, home entertainment, computer gaming, and a growing number of other applications in which consumers are used to a much better sound experience.

By far the surround sound technology can be classified in to two:

• The older analog matrix technology or the 4-2-4 processing system developed by Dolby Laboratories that works by mixing 4 streams of information on to the available two  normal stereo tracks. Though the technique is successful in simulating a richer environment, but there really is no more data delivered to the audience ear than what is already present in the two original channels.
  
• In contrast the newer digital discrete technology offers increased accuracy as sounds can be placed precisely around the listener. In this technique each individual channel is recorded on its own channel within the audio soundtrack, producing a more clearly isolated surround effect. It also offers increased impact thanks to a dedicated low-frequency channel for effects that can literally be felt rather than just heard.

Creating an entirely new category, dubbed as “virtual surround sound” are systems available which deliver surround sound experience by utilizing only two speakers. With a complete 5.1 speaker system, there are speakers located around the room, all directed toward the "sweet spot" like your couch or favorite chair. Whereas in virtual surround sound, special algorithms (e.g., Sound Retrieval System [SRS] and other proprietary algorithms) are created to simulate the effects of full surround sound. When a 5.1 audio signal is processed by one of these systems, some of the signals are delayed, while others use the reflective properties of your walls to recreate a surround-sound effects of speakers to the sides and rear.

Virtual surround system offer a rather small sweet spot and the surround effect may vary to each listener based on their location to the sweet spot. Further virtual surround sound implementation doesn’t come anywhere close to resembling a true surround sound system. So we shall focus only on the true surround sound formats (that is, those that rely of multiple dedicated speakers).

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