Where Is Sound Garden From

Surround Sound

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Our five senses have been honed through the ages to allow us a better chance of survival, essentially permitting us to keep swimming in the gene pool. And while evolution has trained us to see the bear approaching us with our eyes, our ears can "see" him even when our eyes can't. In fact, without the assistance of visual cues, our ears allow us to roughly locate the bear's direction and distance from us within our 3D world.

And while 3D holographic visual displays are still some years away from being practical for consumer use, 3D audio "displays" are here now, and have forever changed the way we experience movies, television and even gaming.

Despite the evolutionary importance of hearing, audiophiles and videophiles continue to debate the relative merits of the two senses. Our eyesight is a wonderful gift, but audio-centrists point out that whereas our eyes take a break each night, our ears never sleep and in fact continually respond to input every moment of our lives. Moreover, peripheral vision notwithstanding, our eyesight is constrained to a narrow angle directly in front of us. In contrast, our ears detect sound from all directions, all around us. Pause for a moment and consider the sounds you are hearing right now from all around–that sensory immersion is truly remarkable.

If that immersion is limited, as in playback over stereo speakers, the realism of the event suffers dramatically. It is true that a room's acoustics can add ambient information to assist the realism of directional sound, but nothing can replace the effect of sound coming from all around. Filmmakers discovered this truth in the 60's as they struggled to compete with the growing popularity of television. By adding surround soundtracks to motion pictures, they could provide a more realistic, more immersive movie-going experience.

The trick worked like a charm, and surround sound design became an important component of movie magic. Now, technological advances have brought surround sound to an even wider audience. Film sound pioneers such as Dolby, SDDS, and DTS have popularized multichannel surround sound for home movie and music playback on DVD-Video, and new audio formats such as DVD-Audio and SACD feature surround sound as well. Whether you are watching movies in a home theater, playing video games or listening to music on a PC, it's more and more likely that the sound is surround.

Stereo provides a sound field in front, but multichannel surround sound provides sound from all around, more like the real world. Generally, surround sound systems employ a 5.1-channel configuration with five satellite speakers and a self-powered LFE (low frequency effects) channel also known as a subwoofer. The LFE is handled apart from the other channels because its function is quite specialized–it must provide very low frequencies at very loud levels, usually below the frequency response of the main upper-bandwidth channels}.

Figure 1: Surround sound speaker placement

The satellite speakers comprise stereo speakers in front along with a center channel speaker, and two (or more) rear surround speakers, as shown in Figure 1. In many cases, these satellites only provide a frequency response of perhaps 150Hz and above. The low frequencies for all channels are provided by the mono subwoofer, taking advantage of the fact that the ears' localization ability is poor at low frequencies (and also poor at very high frequencies). Because the long wavelengths of low frequencies make them inherently omni directional, bass can come from one position in the room, and not be localized by the listener. The main speakers are usually driven by a multichannel receiver that in turn receives signals from a DVD player, Digital Broadcast System (DBS) receiver, multichannel PC sound card, or other source.