| Surround sound is the concept of expanding | | | | film soundtrack. |
| the spatial imaging of audio playback from 1 | | | | |
| dimension (mono/Left-Right) to two or three | | | | The difference between Dolby Digital (AC-3) |
| dimensions. It is often employed for a more | | | | and DTS is: |
| realistic audio environment, actively | | | | |
| implemented in cinema sound systems, | | | | -DTS provides a deeper and tighter low |
| technical theatre, home entertainment, video | | | | frequency presence |
| arcades, computer gaming, and a growing | | | | |
| number of other applications. Many popular | | | | -DTS allows the sound to breath - |
| surround sound formats have evolved over the | | | | transparency |
| years. They include ambisonics, quadraphonic, | | | | |
| Dolby 5.1 Surround sound, DTS, and MP3 | | | | -AC-3 leaves the impression that something is |
| Surround. | | | | missing from the mix |
| | | | |
| Surround sound can be created using several | | | | -At lower bit-rate AC-3 starts to sound like |
| methods. The simplest to understand uses | | | | MP3's encoded at a low-quality 96kbps |
| several speakers around the listener to play | | | | (artifacts) |
| audio coming from different directions. | | | | |
| Another approach involves processing the | | | | DTS is more three dimensional. The sound |
| audio using psychoacoustic sound localization | | | | actually moved forward from the individual |
| methods to simulate a 3D sound field using | | | | speakers to sound more full. This fullness |
| headphones. The third approach, wave field | | | | was most apparent with the music. Instead of |
| synthesis, uses a very large number of | | | | simply coming from the speakers, the DTS |
| speakers to generate the "audio hologram" of | | | | filled the front soundstage not only side to |
| the original audio in the whole room (as of | | | | side, but with more depth as well. Bass |
| 2004 the only commercial implementation of | | | | reproduction was also more defined in the DTS |
| this is Iosono). Surround sound is not | | | | version, leaving the DD edition sounding |
| limited to placement of speakers along a flat | | | | muddy. |
| (2-dimensional) plane. Vertically-located | | | | |
| audio sources can be considered. | | | | Dolby Digital incorporates dialog |
| | | | normalization, which alters the decoded level |
| Dolby Digital (DD) uses the AC-3 file format, | | | | of the soundtrack. The typical setting |
| which any Dolby Digital Decoder can decode to | | | | reduces level by 4 dB; other reduction levels |
| produce 5.1 audio. Dolby Digital is the | | | | are possible. In most decoders, this leads to |
| technical name for Dolby's multi-channel | | | | a reduction in signal-to-noise and dynamic |
| digital sound coding technique, more commonly | | | | range. |
| referred to as Dolby 5.1. A six-channel sound | | | | |
| coding process originally created by Dolby | | | | Dolby Digital also provides a "stereo down |
| for theaters, AC-3 was subsequently adapted | | | | mixing" feature as a substitute for a |
| for home use and is now steadily becoming the | | | | dedicated stereo mix. However, many |
| most common sound format for DVD. | | | | production engineers have admitted that they |
| | | | often have to modify the original 5.1 mixes |
| Six discrete audio channels: | | | | in order to attain acceptable stereo down |
| | | | mixes. Therefore, the 5.1 mix on many Dolby |
| -3 for speakers at the front - left (L), | | | | Digital DVDs may differ from the original |
| center (C), and right (R) | | | | master. |
| | | | |
| -2 for surround speakers at the side or rear | | | | 5.1 Surround Sound Headphones: |
| - surround left (SL) and surround right (SR) | | | | |
| | | | While the traditional method of surround |
| -1 low-frequency effects (LFE) channel | | | | sound described above uses numerous speakers |
| carries supporting deep bass sound effects, | | | | to produce the entire sound field, the |
| ranging from 10 Hz to 120 Hz, which can for | | | | surround sound mix is limited to a |
| example be used by a subwoofer. (This is the | | | | two-channel stereo mix when using headphones. |
| '.1' in '5.1'.) | | | | That is why recent developments in surround |
| | | | sound technology include 5.1 surround sound |
| DTS is an encode/decode process that delivers | | | | headphones, to allow you to have the same |
| 5.1 channels of "master quality" audio on CD, | | | | sound quality and surround sound experience |
| CD-R, and DVD. Each DTS encoded disc | | | | without waking the neighbors or disturbing |
| represents a sonic "clone" of the original | | | | roommates. |