How Surround Sound Works

By: Tom Harris

Digital Domain: SDDS

The latest entry in cinema digital sound, Sony Dynamic Digital Sound® (SDDS), boasts five separate channels at the front of the theater as well as left and right surround channels, for a total of eight available channels including the subwoofer.

Like Dolby Digital, SDDS encodes digital information with a distinct pattern of light and dark areas on film. In this case, the reader includes a laser on one side of the film and an array of photocells on the other side. The laser passes light through transparent areas of the film, but not through opaque areas. The photocells that are not exposed to light pass a small current on to the processor, but the exposed photocells do not. In this way, the processor receives the digital pattern, which it interprets as a sound signal. Unlike the other digital formats, SDDS uses two identical digital tracks to allow for better error correction.


Dolby and DTS have both released home theater versions of these popular formats, and there is a SDDS Surround 7.1® system (seven audio channels and a subwoofer channel) available for consumers. While digital sound cannot be recorded on video tape or broadcast over conventional cable, it is the only way to encode information on DVD. Digital sound is also broadcast on satellite systems, as well as digital cable. Check out How Home Theater Works to learn all about these home systems.

For movie fans everywhere, surround sound has become an integral part of the theater experience. And for moviemakers, putting together the surround mix has become a crucial step in the production process. Surround sound has effectively expanded movies into three dimensions, putting the audience in the middle of the action like nothing else can.

To learn more about surround sound, including its long history and technical details about particular systems, check out the links below.

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