Deciphering Surround Sound Essay Research Paper DECIPHERING

Deciphering Surround Sound Essay, Research Paper

DECIPHERING SURROUND SOUND

FOR HOME THEATER

In recent years there have been many advancements in the world of home entertainment, arguably the most popular of these being the inset of theater quality Surround Sound at home. The dramatic growth and popularity of surround sound has spawned more and more companies trying to get their piece of the action. The obvious advantage of this competition is constantly advancing technologies and great variety in products that span every price point and budget. The downside to all of this variety and cutting edge technology is the often confusing learning curve and deciding which system will best suite your home entertainment needs. The following information should help dispel the mystery of surround sound and bring you up to date with the most recent developments. Though there are other brands and formats out there to choose from we are going to focus on the three most popular and successful companies in the surround sound world today, Dolby Labs, Digital Theater Systems, and LucasFilm. We ll start with Dolby Labs and their older, but still in wide use, formats: Dolby Surround and Dolby Pro-Logic.

The Dolby Surround process involves encoding four channels of information–Front Left, Center, Front Right, and Rear Surround into a two-channel signal. A decoding chip then decodes the four channels and sends them to the appropriate destination, the Left, Right, Rear, and Phantom Center. The center channel is derived from the L/R front channels not a center speaker. The result is a more balanced listening environment in which the main sounds derive from the left and right channels, the vocal or dialog emanates from the center phantom channel, and the ambience or effects information comes in from behind the listener. The sensation of sounds moving from front to rear and left to right adds more realism to the viewing/listening experience by placing the viewer in the action. Dolby Surround is easily useful in both musical and film sound recording.

Dolby Surround does have its limitations, however. With the rear channel being basically passive, it lacks precise directionality. Also, overall separation between channels is much less than a typical Stereophonic recording. Dolby Pro-Logic addresses this issue by adding hardware elements in the decoding chip that emphasize important directional cues in a movie soundtrack. In other words, the decoding chip will add emphasis to directional sounds by increasing the output of the directional sounds in their respective channels. This process is very effective for film soundtracks and adds more accuracy to effects such as explosions, planes flying overhead, etc. There is greater separation between channels. In addition, Dolby Pro-Logic extracts a dedicated Center Channel that more accurately centers the dialog which created the need for a fifth speaker dedicated to the center channel. Although Dolby Pro-Logic is an excellent refinement of Dolby Surround, its effects are derived strictly in the reproduction process, and even though the rear surround channel employs two speakers, they are still passing a monophonic signal limiting motion and sound placement cues. This brings us to Dolby Labs current and most popular format called Dolby Digital, also known as AC-3, or 5.1 Surround

Dolby Digital adds both accuracy and flexibility by adding stereo rear surround channels that enable sounds to emanate in more directions, as well as a dedicated Subwoofer Channel to provide more emphasis for low frequency effects. Dolby Digital is often referred to as a 5.1 channel system, which stands for five discrete surround channels plus the one dedicated subwoofer channel. Unlike Dolby Pro-logic, which requires a rear channel of only minimal power and limited frequency response, Dolby Digital encoding/decoding requires the same power output and frequency range as the main channels. Dolby Digital encoding on DVDs, laserdiscs, and satellite programming is very common and has solidified this format in the marketplace. Since Dolby Digital involves its own encoding process, you need to have a Dolby Digital receiver or amplifier to accurately decode the signal.

Dolby Labs, however, is not the only player in the home surround sound market. Digital Theater Systems has also adapted its surround sound process for home use. It is a 5.1 system just like Dolby Digital, but since DTS uses less compression in the encoding process, many feel that DTS has a better result on the listening end. In addition, while Dolby Digital is mainly intended for the movie soundtrack experience, DTS is also being used in the mixing and reproduction of musical performances. Although DTS is a 5.1 system, a DTS-equipped amplifier or receiver is required to accurately decode the signals imprinted on DTS-encoded media.

Finally we have THX (Tomlinson Holman Experiment) owned by LucasFilm ltd. Many consumers are under the impression that THX is an altogether different surround sound system when in actuality it is just a certification program that manufacturers use to see if they meet the standards that LucasFilm has set for optimal surround sound performance. The idea is that sound tracks under THX are reproduced exactly as the filmmaker intended. Components, from receivers and amps to speakers, have to meet certain performance and construction requirements in