Glossary
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31 definitions for D
DAC : Digital-to-analogue converter, turning on/off pulses into analogue sound. CD players have DACs built in. Separate DACs can upgrade a CDplayer or other digital player/ recorder, or can be used with dedicated CD transports.
DAT : Digital Audio Tape. A digital recording system now used mainly professionally. Uses a revolving recording head similar to that used in a VCR.
Data reduction : Lowers the amount of data needed to store music. Sony's MiniDisc uses an in-house system called ATRAC (Adaptive Transform Acoustic Coding) while the PASC (Precision Adaptive Sub-band Coding) used in Philips' DCCformat serves a similar function, removing signals its designers think you can't hear.
DCC : Digital Compact Cassette - Philips' home digital tape system, now rather knocked out by Sony's MiniDisc.
DDD : On CD cases - music recorded digitally, mastered digitally and stored digitally on CD.
Decibel : (dB) Measures changes in sound pressure. A change of 1dB is just about audible, while +10dB sounds like the level has been doubled.
Digital Output : Allows the digital signal to be recorded or processed by an offboard DAC. Electrical or optical (fibre optic) outputs are provided.
Digital Radio : Digital stereo service currently broadcast by both the BBC and independent stations, it banishes hiss and interference. Also offers extra services, such as archive music on BBC 6, 'talking book' stuff on OneWord, and so on. Currently relatively few tuners available, with hi-fi models from Arcam, Cambridge Audio, Cymbol, Sony, TAG McLaren Audio, Technics and Videologic/Pure.
Dispersion : Describes the radiation pattern of sound waves from a sound source (the sound source being a speaker in terms of audio/video); definition of the amount of air all around a speaker excited by the sound waves it produces. Think of a flashlight and the light it gives off. The light angles out to the sides as it moves away from the flashlight creating a larger and larger spot of light. This is the flashlight's dispersion. A laser-beam has a very narrow dispersion (it's light is very focused and does not angle out much at all). A spotlight has a wide dispersion (its light angles out to fill a vast amount of space). Speaker dispersion operates essentially in the same way with sound waves taking the place of light beams. Dispersion in speakers is most frequently quoted as an angle in degrees from the center of the speaker related to the sound pressure levels generated at that angle. As you move farther away from the centerline of the speaker, the sound level dies off (just like how the light at the center of a flashlight's spot of light is brighter than that at its outer edges). A speaker with a wide dispersion sprays sound out in a wide angle with the sound being of a reasonable level. A speaker with a narrow dispersion is more like a laser, directing its sound in a very specific area.
+ Associated link: http://www.audiovideo101.com/dictionary/dispersion.asp
Distortion : Unwanted signals or signal changes added by equipment.
Dolby 3 Stereo : In cinema sound amps, delivers the surround channel information through the front left and right speakers, while providing centre channel information.
Dolby B, C & S : Noise-reduction to boost quiet signals when recording and reduce them on playback, cutting hiss.
Dolby Digital : Also known as AC-3, this is the latest home cinema sound system from Dolby, using five discrete channels of digital sound plus a separate subwoofer channel.
Dolby Digital Surround EX : Development of Dolby Digital 5.1 surround audio that includes a matrixed centre-rear audio signal to provide additional surround envelopment. Requires a suitable decoder, with amplification, and either one or two additional centre rear speakers. See also THX Surround EX.
Dolby HX Pro : Not noise reduction, but a way to record more high frequency information without distortion (often called 'increasing headroom').
Dolby labs : Developed noise-reduction and cinema surround systems.
Dolby Pro-Logic : Uses an extra centre speaker at the front, which locks dialogue to the screen. Now mainly used when viewing material sourced from video tape or off-air broadcasts, or with older soundtracks on DVD lacking discrete surround channels.
Dolby Pro-Logic II : Enhanced version of the original Pro-Logic, with improved channel steering for an effect closer to that available from true Dolby Digital source material. Also capable of extremely good effects with stereo material when using the Music mode.
Dolby Surround : Encodes sound for rear effects channels into the stereo tracks. Needs to be replayed through a decoder to produce surround.
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