Surround sound
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- "Surround" redirects here. For the video game called "Surround", see Light Cycle.
Surround sound is the concept of expanding the spatial imaging of audio playback from one dimension (mono/Left-Right) to two or three dimensions.
This is often performed for a more realistic audio environment, actively implemented in cinema sound systems, technical theatre, home entertainment, video arcades, computer gaming, and a growing number of other applications.
Many popular surround sound formats have evolved over the years. They include discrete 5.1 Surround sound on DVD-Audio (DVD-A) or SACD (Super Audio CD), ambisonics, quadraphonic, Dolby 5.1 Surround sound, DTS, DVD-Video (DVD-V), and MP3 Surround.
Surround sound can be created using several methods. The simplest to understand uses several speakers around the listener to play audio coming from different directions. Another approach involves processing the audio using psychoacoustic sound localization methods to simulate a 3D sound field using headphones. The third approach, which is based on Huygens' principle, attempts to reconstruct the recorded soundfield wavefronts within the listening space and so might be regarded as a form of "audio hologram". There are two related forms of this approach,[1] the first of which, Ambisonics, provides an exact reconstruction at a central point and a less and less accurate reconstruction as you move away from this point. The second form, wave field synthesis or WFS, produces a soundfield which, whilst not absolutely accurate anywhere, has an even error field over the whole area. WFS (of which two commercial systems are available, one from the Swiss company sonic emotion and one from Iosono) requires a large number of loudspeakers and a considerable amount of computing power to produce its results whereas Ambisonics, for which there is a significant amount of both free and commercial software available (as well as some hardware from, for instance, Meridean) requires far fewer resources, at least in its simplest form (this is no longer so true for more recent developments such as Near Field Compensated Higher Order Ambisonics[2]). In the limit, WFS and Ambisonics converge as was shown some years ago by Rozzenn Nicol and Marc Emerit[3] but for the present Ambisonics has a far greater market penetration in the domestic arena and especially amongst musicians involved in electronic and computer music. Some consumer electronic devices (AV receivers, stereos, and computer soundcards) have digital signal processors or digital audio processors features built into them to simulate surround sound from stereo sources.
Though generally the province of big-budget movie productions and sophisticated video games, some consumer camcorders (particularly DVD-R based models from Sony) have surround sound capability either built-in or available as an add-on. Though considered by camcorder reviewers to be of dubious utility, it is nevertheless one of the few ways that someone not using professional equipment can create surround sound. (The MiniDV spec does allow up to four channels of sound, making it theoretically possible for such camcorders, but it is seldom implemented that way.)
[edit] Surround sound specifications
For the following sections, a distinction is made between the number of discrete channels encoded in the original signal, and the number of channels that are reproduced for playback; these can be added using matrix decoding. A distinction is also made between the number of channels reproduced for playback, and the number of speakers over which these channels are played. Graphics to the right of each section represent the number of channels, not the number of speakers used.
Additionally, 4.1, 5.1, 6.1, and 7.1 formats make use of bass management, which allows sound that is below the abilities of main channels (5.0 channels) to be redirected to the subwoofer, which is designed to handle that frequency range. There are notation differences between the pre-bass-managed signal and once it has passed through bass manager. For example, in 5.1, the channels are referred to as L(eft), R(ight), C(enter), L(ow )F(requency)E(effects), S(urround)L(eft), and S(urround)R(ight). However, once passing through the bass manager, they are referred to as L(eft), R(ight), C(enter), Sub(woofer), S(urround)L(eft), and S(urround)R(ight).
[edit] 3.0 Channel Surround (analog matrixed: Surround)
Extracts 3 audio channels from a stereo source:- Two channels for speakers at the front - left (L) and right (R).
- One channel for surround speaker at the rear - surround (S).
- Describes the earliest matrixed Dolby Surround system.
- Speaker placement: (3 speakers in total) Three identical speakers placed equidistant around a central listening position.
[edit] 4.0 Channel Surround (analog matrixed: Quadraphonic)
Extracts 4 audio channels from a stereo source:- Two channels for speakers at the front - left (L) and right (R).
- Two channels for surround speakers at the rear - surround left (LS) and surround right (RS).
- Describes the early matrixed Surround Quadraphonic, Quadraphonic Stereo system. Source media, usually records or tape is often branded 4 channel stereo.
- Speaker placement: (4 speakers in total) The front speakers should be placed at the edges of the screen, toed in to face the central listening location, and the tweeters should be ear height. Rear channel speaker should be placed high on the back wall, slightly behind the listening position, and can be of smaller size, due to the frequency limitations of the surround channel.
[edit] 4.1 Channel Surround (analog matrixed: Dolby Prologic)
Extracts 4 audio channels, and 1 LFE channel from a stereo source:- Two channels for speakers at the front - left (L) and right (R).
- One channel for speaker at the center - center (C).
- One channel for both surround speakers at the rear - mono surround channel (S).
- One low-frequency channel using a sub-woofer (LFE).
- Describes the Dolby Prologic matrixed Surround system. Source media, usually VHS, Laserdisc or television broadcast, CableTV/Satellite is often branded with "Dolby Surround" logo.
- Surround Sound speaker placement: (6 speakers in total) The front speakers should be placed at the edges of the screen, toed in to face the central listening location, and the tweeters should be ear height. The center speaker should be placed behind the screen (when using projection) or over or under a tv, and as close to ear high as possible. Rear channel speakers should be placed high on side walls, slightly behind the listening position, and can be of smaller size, due to the frequency limitations of the surround channel.
[edit] 5.1 Channel Surround (analog matrixed: Dolby Prologic II)
Extracts 5 audio channels and 1 LFE channel from a specially encoded stereo source:- Two channels for speakers at the front - left (L) and right (R).
- One channel for speaker at the center - center (C).
- Two channels for surround speakers at the rear - surround left (LS) and surround right (RS).
- One low-frequency channel using a sub-woofer (LFE).
- Describes the Dolby Prologic II matrixed Surround system. Source media, usually PS2 or Gamecube is often branded with "Pro-Logic II" logo.
- Surround Sound speaker placement: (6 speakers in total) The front speakers should be placed at the edges of the screen, toed in to face the central listening location, and the tweeters should be ear height. The center speaker should be placed behind the screen (when using projection) or over or under a tv, and as close to ear high as possible. Rear channel speakers should be placed high on side walls, slightly behind the listening position, and should have a di-pole construction.
[edit] 5.1 Channel Surround (digital discrete: Dolby Digital, DTS)
Delivers 5 audio channels and 1 LFE channel from a 6 channel source:- Two channels for speakers at the front - left (L) and right (R).
- One channel for speaker at the center - center (C).
- Two channels for surround speakers at the rear - surround left (LS) and surround right (RS).
- One low-frequency channel using a sub-woofer (LFE).
- Describes the Dolby Digital and DTS Surround systems. Source media, usually DVD and sometimes Laserdisc or satellite/digital cable is often branded with "Dolby Digital" and/or DTS logos.
- DTS uses a higher sampling rate than Dolby Digital, thus DTS uses less compression and achieves higher fidelity than Dolby Digital.
- Surround Sound speaker placement: (6 speakers in total) Surround Sound speaker placement is different for both music and movie content.
For music speakers are placed in a circle around the listener. The center channel has 0º offset, left and right are offset ± 30º, and the left/right surrounds are offset by ±110º. Also all speakers should be, monopole, equidistant to the listener, and all delay (ms) calculations on the surround decoder should be turned off (0ms).
For movie surround, the front speakers should be placed at the edges of the screen, toed in to face the central listening location, and the tweeters should be ear height. The center speaker should be placed behind the screen (when using projection) or over or under a tv, and as close to ear high as possible. Rear channel speakers should be placed high on side walls, slightly behind the listening position, and should have a di-pole construction.
[edit] 6.1 Channel Surround (analog matrixed: Dolby Prologic IIx)
Extracts 6 audio channels and 1 LFE channel from a specially encoded stereo source:- Two channels for speakers at the front - left (LF) and right (RF).
- One channel for speaker at the center - center (C).
- Two channels for surround speakers at the sides - side left (L) and side right (R).
- One channel for both surround speakers at the rear - mono surround channel (S).
- One low-frequency channel using a sub-woofer (LFE).
- Describes the Dolby Prologic IIx matrixed Surround system. Source media is unknown.
- Surround Sound speaker placement: (8 speakers in total) Surround Sound speaker placement is different for both music and movie content.
For music speakers placement is unknown
For movie surround, the front speakers should be placed at the edges of the screen, toed in to face the central listening location, and the tweeters should be ear height. The center speaker should be placed behind the screen (when using projection) or over or under a tv, and as close to ear high as possible. Side channel speakers should be placed high on side walls, to the left and right of the listening position, equidistant from the front speakers and the rear speakers. Rear channel speakers should be placed high on side walls, slightly behind the listening position, and should have a di-pole construction.
[edit] 6.1 Channel Surround (digital discrete: Dolby Digital EX with a matrixed 6th channel)
Delivers 5 audio channels, 1 extracted audio channel and 1 LFE channel from a 6 channel source:
- Two channels for speakers at the front - left (LF) and right (RF).
- One channel for speaker at the center - center (C).
- Two channels for surround speakers at the sides - side left (L) and side right (R).
- One channel for both surround speakers at the rear - mono surround channel (S).
- One low-frequency channel using a sub-woofer (LFE).
- Describes the Dolby Digital EX discrete/matrixed hybrid Surround system. Source media, usually DVD is often branded with "Dolby Digital EX" logo.
- Surround Sound speaker placement: (8 speakers in total) Surround Sound speaker placement is different for both music and movie content.
For music speakers placement is unknown
For movie surround, the front speakers should be placed at the edges of the screen, toed in to face the central listening location, and the tweeters should be ear height. The center speaker should be placed behind the screen (when using projection) or over or under a tv, and as close to ear high as possible. Side channel speakers should be placed high on side walls, to the left and right of the listening position, equidistant from the front speakers and the rear speakers. Rear channel speakers should be placed high on side walls, slightly behind the listening position, and should have a di-pole construction.
[edit] 6.1 Channel Surround (digital discrete: DTS-ES)
Delivers 6 audio channels and 1 LFE channel from a 7 channel source:
- Two channels for speakers at the front - left (LF) and right (RF).
- One channel for speaker at the center - center (C).
- Two channels for surround speakers at the sides - side left (L) and side right (R).
- One channel for both surround speakers at the rear - mono surround channel (S).
- One low-frequency channel using a sub-woofer (LFE).
- Describes the DTS ES discrete Surround system. Source media, usually DVD is often branded with "DTS ES" logo.
- Surround Sound speaker placement: (8 speakers in total) Surround Sound speaker placement is different for both music and movie content.
For music speakers placement is unknown
For movie surround, the front speakers should be placed at the edges of the screen, toed in to face the central listening location, and the tweeters should be ear height. The center speaker should be placed behind the screen (when using projection) or over or under a tv, and as close to ear high as possible. Side channel speakers should be placed high on side walls, to the left and right of the listening position, equidistant from the front speakers and the rear speakers. Rear channel speakers should be placed high on side walls, slightly behind the listening position, and should have a di-pole construction.
[edit] 7.1 Channel Surround (digital discrete: Dolby Digital Plus, DTS-HD)
Delivers 7 audio channels and 1 LFE channel from an 8 channel source:
- Two channels for speakers at the front - left (LF) and right (RF).
- One channel for speaker at the center - center (C).
- Two channels for surround speakers at the sides - side left (L) and side right (R).
- Two channels for surround speakers at the rear - surround left (LS) and surround right (RS).
- One low-frequency channel using a sub-woofer (LFE).
- Describes the Dolby Digital Plus discrete Surround system. Source media, usually HD-DVD and sometimes Blu-Ray is often branded with "Dolby Digital Plus" and/or DTS-HD logos.
- Surround Sound speaker placement: (8 speakers in total) Surround Sound speaker placement is different for both music and movie content.
For music speakers placement is unknown
For movie surround, the front speakers should be placed at the edges of the screen, toed in to face the central listening location, and the tweeters should be ear height. The center speaker should be placed behind the screen (when using projection) or over or under a tv, and as close to ear high as possible. Side channel speakers should be placed high on side walls, to the left and right of the listening position, equidistant from the front speakers and the rear speakers. Rear channel speakers should be placed high on side walls, slightly behind the listening position, and should have a di-pole construction.
[edit] 8 Channel Surround (digital discrete: Dolby Digital HD, DTS-HD Master Audio)
Dolby Digital HD and DTS-HD Master Audio are emerging 8 channel home surround systems currently supported with HD-DVD and Blu-Ray DVD.
Cinematic 8 channel audio is a commercial surround sound standard that adds two speakers to the more conventional, and consumer-oriented 6-channel (5.1) audio set-up. 8-channel positional audio utilizes the standard front, center, and LFE (bass) speaker configuration, but in addition, includes two speakers positioned by the side and two by the backside. Using such a sound configuration, almost every angle of sound can, theoretically, be captured for a completely immersive experience.
But the 8-channel format has another, even more well-established tradition. The history of 'electronic music' includes the evolution of multi-channel playback in concert (arguably the real roots of 'surround sound' for cinema) and for a considerable time the 8-channel format was a de facto standard. This standardisation was fostered, in great measure, by the development of professional and semi-professional 8-track tape recorders - originally analog, but later manifesting in proprietary cassette formats by Alesis and Tascam. The speaker configuration, however, is much less traditional, and unlike cinematic reproduction systems, there is no hard-and-fast 'standard'.
In fact, composers took (and to some extent still take) considerable interest in experimenting with speaker layouts. In these experiments, the goal is not limited to creating 'realistic' playback of believably natural sonic environments. Rather, the goals are frequently simply to experience and understand the effect created by variations on source and imaging.
[edit] 10.2 Channel Surround
10.2 is the surround sound format developed by THX creator Tomlinson Holman of TMH Labs and University of Southern California (schools of Cinema/Television and Engineering). Developed along with Chris Kyriakakis of the USC Viterbi School of Engineering, 10.2 refers to the format's slogan: "Twice as good as 5.1". It has been touted as the audio equivalent of IMAX - spectacle beyond what can be achieved by any other format.
10.2 augments the LS (left surround) and RS (right surround) channels by two point surround channels that can more finely manipulate sound - allowing the mixer to shift sounds in a distinct 360° circle around the movie watcher.
The 14 discrete channels are:
- Five front speakers: Left Wide, Left, Center, Right and Right Wide
- Five surround channels: Left Surround Diffuse, Left Surround Direct, Back Surround, Right Surround Diffuse and Right Surround Direct
- Two LFE channels: LFE Left, LFE Right
- Two Height channels: Left Height, Right Height
The .2 of the 10.2 refers to the addition of a second subwoofer. The system is bass managed such that all the speakers on the left side use the left sub and all the speakers on the right use the right sub. The Center and Back Surround speaker are split among the two subs. The two subs also serve as two discrete LFE (Low Frequency Effects) channels. Although low frequencies are not localizable, it was found that splitting the bass on either side of the audience increases the sense of envelopment.
[edit] Notation
This notation, e.g. '5.1', reflects the number of full range, discrete channels; including a ".1" to reflect the limited range of the LFE channel.
e.g. 5 full-range channels + 1 LFE channel = 5.1
It can also be expressed as the number of full-range channels in front of the listener, separated by a slash from the number of full-range channels beside or behind the listener, separated by a decimal point from the number of limited-range LFE channels.
e.g. 3 front channels + 2 side channels + an LFE channel = 3/2.1
This notation can then be expanded to include the notation of Matrix Decoders. Dolby Digital EX, for example, has a sixth full-range channel incorporated into the two rear channels with a matrix. This would be expressed:
3 front channels + 2 rear channels + 3 channels reproduced in the rear in total + 1 LFE channel = 3/2:3.1
Note: The term stereo, although popularised in reference to two channel audio, can also be properly used to refer to surround sound.
[edit] See also
- 10.2
- 3D audio effect
- Ambisonics
- Cinema Digital Sound
- DTS
- Dolby
- DVD-Audio
- Haas effect
- Matrix Decoder
- MP3 Surround
- Penteo
- Quadraphonic
- Super Audio CD
- Sound card
- Soundfield microphone
- Surround Sound Test CD
- Virtual surround
- Wave field synthesis
- WZLXaf:Ruimteklank
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