D-connector : See D-sub(miniature) connector.

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D-sub(miniature) connector : Also called a D-connector, or a D-type connector. A type of connector commonly found on computers and data transmission devices, including SCSI devices and computer monitors. D-type connectors have a "D-shaped" angled housing, and have 9-pin, 15-pin, and 25-pin configurations, designated DE-9, DA-15, and DB-25, respectively.

 

D-type (connector) : See D-sub(miniature) connector.

 

D.C. : Da Capo. Italian for "Head," meaning "Play from the beginning."

 

D.S. : Dal Signo. "Play from the sign(D)."

 

D/A : See digital-to-analog converter.

 

DAC : See digital-to-analog converter.

 

DAE : (1) Digidesign Audio Engine.™ A Macintosh application that can run behind other applications, such as sequencers or ProTools,™ handling the transfer of audio data to/from the hard disk. DAE is licensed by many sequencer developers to avoid writing their own low-level I/O code.

(2) Digital Audio Extraction. The process of capturing CD-Audio tracks digitally from a CD-ROM drive to hard drive, using software such as Astarte’s CD Copy™ or OMI’s Disc-to-Disk.™"

 

dailies : Uncut footage shot each day during production. If picture editing is on film, with picture and synchronized magnetic film, those elements when edited together become the workprint and worktrack. Used to chart the progress of the film and for preliminary music cuts. Also called rushes.

 

daisy chain : See serial(2).

 

damping : (1) Damping is the addition of friction to a resonance in order to remove energy from a mechanical system, reducing the magnitude of vibration at resonant frequencies. For example, the reduction of movement of a speaker cone, due either to the electromechanical characteristics of the speaker driver and suspension, or the effects of pressure inside a speaker enclosure. The electrical analog of friction is resistance, and it is used to damp resonating electrical circuits, such as crossover networks and filters. See also Q. (2) Acoustic fiberglass material used inside speaker enclosures."

 

damping factor : (1) A factor defined as the rated load divided by the amplifier output impedance. (2) The ability of an amplifier to control the motion of a loudspeaker cone after a signal disappears, i.e., its ability to defeat the natural ringing tendency of the body (cone) in motion. An amplifier with a high damping factor looks more like a kind of short circuit to the speaker, reducing its vibration when the signal stops. The damping factor of an amplifier will vary with frequency, and sometimes a manufacturer will publish a curve of damping factor vs. frequency. The effect of high damping factors is most audible at low frequencies, where the primary resonance of the woofer cone, called hangover, is reduced in level.

 

DAR : See Digital Audio Recorder. Any type of audio recording system which records upon a digital medium, such as DAT or hard disk. DAT or DCC recorders, digital dubbers, digital multitracks, and hard-disk recording systems are all example of digital audio recorders. These recorders are an alternative to analog recorders, such as traditional cassette or reel-to-reel formats which do not convert the waveform to a digital representation prior to writing it to the recording medium.

 

darkness : The amount of low-frequency, or corresponding lack of high-frequency, components of a sound. Reverberation from distant objects usually has fewer high frequencies and sounds darker than reverb from close objects. The opposite of brightness.

 

DASH : Digital Audio Stationary Head. A standard format for ensuring compatibility between Sony PCM-model digital multitrack recorders which that use stationary, rather than rotating heads. Originally, the DASH format was designed to support 2-track, 8-track, 16-track, and 24-track recorders using reel-to-reel tape. The 8-track and 16-track machines were never marketed, and a 2-track model is no longer in production. The DASH specification now includes double-density, thin-film heads that allow 48-track recording on the same tape originally used by the 24-track devices. DASH-format machines are backward compatible: 24-track machines can be used with newer models, and a project can be started on a 24-track machine and completed on a 48-track recorder, if needed, as the data from tracks 25-48 are written into the spacing between the original 24 tracks. DASH tapes run 30ips at up to 48kHz, with 44.1kHz and other sampling rates supported. In addition to 24-track or 48-track recording, DASH format provides two analog cue tracks and one track each for control and timecode signals. The format covers a wide range of versions, such as from 2-48 tracks and tape speeds from 12-76cps, and was agreed on by Sony and Studer, among others. DASH format recorders are currently manufactured by Sony and Studer. See also S-DAT, ProDigital.

 

DAT : Digital Audio Tape. There are two formats: R-DAT which uses a rotating head assembly similar to a VCR, records diagonally across the tape, and includes a four-channel format which would permit recording of ambisonics; and the S-DAT which uses a stationary head and records several linear, parallel tracks of digital signals. There are no known commercial S-DAT products. The DAT standard format specifies a small cassette that provides up to two hours of 16-bit, linear, sequential monaural, PCM digital recording at a sampling rate of 32kHz, 44.1kHz, or 48kHz. Also called a DCAC, Digital Compact Audio Cassette. See also Digital Compact Cassette.

 

data compression : See compression(3).

 

data controller : A controller change message which is used to set some parameter in the receiving device, for example,

 

the data increment and decrement switches on a synthesizer.

 

data dump : A packet of memory contents being transmitted from a sending device to a receiving device, usually in the form of MIDI System-Exclusive data, or stored in RAM. Also called a bulk dump or block transfer.

 

data slider : A pot fitted to a device such as a synthesizer which allows parameters within the device to be adjusted for programming, etc."

 

data thinning : A sequencer software feature which allows programs and/or devices to reduce the amount of MIDI data produced by continuous controllers such as pitch-bend, aftertouch, etc. This is accomplished by only keeping the continuous controller data when the parameter changes, as opposed to sending all bytes of data all of the time.

 

datafiler : A portable device for the replay of previously recorded MIDI data, used in live performances.

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DAW : (Digital Audio Workstation) A computer production program capable of recording, mixing, and manipulating audio files. Including the ability to simulate analog workstation functions & hardware. 

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dB : See decibel.

 

DB-9 connector : An industry-standard connector for serial machine control of professional audio and video transports. Developed by Sony, also called the Sony 9-pin.

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DBS : Direct Broadcast Satellite. See AC-1.

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dbx™ noise reduction : a noise reduction system that uses a companding noise reduction to reduce noise. Dbx is connected into a recording system in the same way that a Dolby system is. It provides up to 30dB of noise reduction, but unlike Dolby noise reduction, the dbx system works over the entire audio frequency range, using a 2:1/1:2 compression/expansion ratio. Dolby-encoded and dBx-encoded tapes are incompatible. Systems using dbx noise reduction are typically more expensive than systems using Dolby."

 

DCA : Digitally Controlled Amplifier. Sometimes short for Digitally Controlled Attenuator. The DCA of a digital synthesizer modifies the amplitude of the signal generated by the DCO. It is the digital analog of a VCA.

 

DCAC : See DAT.

 

DCC : See Digital Compact Cassette.

 

DCO : Digitally Controlled Oscillator. The microprocessor-controlled sound generator used in a digital synthesizer. The DCO directly generates the original signal that is used as the fundamental for the sounds created by the synthesizer. The keyboard tells the DCOs what pitch to produce; the audio signal may then be altered by sound modifiers, including a DCW, DCA, differentiators and integrators, and various modulators and limiters. The digital equivalent of the analog VCO.

 

DDL : Digital Delay Line. See delay line.

 

de-emphasis : The complementary equalization which follows pre-emphasis. Sometimes redundantly called post de-

emphasis.

 

de-esser : A special type of compressor that operates only at high frequencies, usually above 3kHz-4kHz. It is used to reduce the effect of vocal sibilant sounds. De-essers are usually used only for vocal music.

 

dead : Acoustically absorptive. The opposite of live. See also LEDE.

​

decade : The interval between two quantities plotted along an axis where the second quantity is ten times the first. A frequency ratio or interval of 10:1, as opposed to an octave, which is a 2:1 ratio. Sometimes the rolloff of a filter or equalizer is expressed in dB/decade, rather than in dB/octave. A rolloff of 20dB/decade is equal to A rolloff of 6dB/octave. The decade interval has no musical significance, but is used in the discussion of logarithmic quantities such as decibels.

 

decay : (1) The time it takes for a sound to reach minimum loudness; the end of a sound.

(2) The second of the four segments of a typical ADSR envelope. The decay control determines the amount of time it takes for the envelope to fall from the peak reached at the end of the attack segment to the sustain level. If no additional energy is put into the sound source (e.g., a cymbal), then the decay is the time during which the sound falls from the loudest point back to silence.

(3) The time taken for reverberation to die away. See decay time, reverberation time,RT-60.

 

decay rate : The number of decibels per second by which echoes or reverberation of a sound diminish once the sound has stopped. Depending on the sound source and environment, the decay rate may be linear, i.e., a constantly decreasing number of dB per second, or it may begin to decay slowly and then fall off rapidly, or the reverse. Also, various frequencies of the sound may decay at different rates.

 

decay time : See reverberation time.

 

Decca trees : A triangular array of omnidirectional microphones , a type of true spaced-microphone recording technique, where the central channel is distributed equally to left and right. This yields a very stable central image, avoiding the hole-in-the-middle which is problematic with many space-pair arrangements. A variant on the Decca tree places three cardioid microphones (L,C,R) in a triangle configuration. In all cases, the width of the tree is typically one-half to one-third the sound field width, and the center microphone is slightly closer to the performers. See binaural recording.

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decibel (dB): A unit of measurement used to indicate audio power level, literally one-tenth of a bel, where the bel is a power ratio of 10:1. Technically, a decibel is a logarithmic ratio of two power measurements, which means that there is no such thing as a dB measurement in isolation. In order to measure a signal in dB, you need to know what power (watts, volts) it is referenced to and the impedance of the reference system.:
 

Number of dBs = 10 log (P1/P2),

where P1 and P2 are the two powers being compared, and where the log is base-10. Impre-cisely, 1dB is the smallest increment in loudness detectable by a careful listener. An increase of about 3dB is a doubling of electrical (or signal) power; an increase of 10dB is ten times more power, but is only a doubling of perceived loudness. Some commonly used power ra-tios, expressed in dB:

 

 

 

 

 

 

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However,

Number of dBs = 20 log (V1/V2),

Where V1 and V2 are the two voltages being compared, and where the log is base-10. This means that the answer is twice what it would be for a ratio of powers. In other words, dou-ble the voltage and the level goes up by 6dB; halve the voltage and the level goes down by 6dB. See Appendix A.
 

 

 

 

 

 

 

Commonly used reference levels are indicated by such symbols as:

 

 

 

 

 

 

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decimation : A form of digital filtering whereby audio data is oversampled and then decimated to the required 44.1kHz. In practice, the sampling rate is 64 or 128 times 44.1kHz. A digital brick-wall filter is then applied to the data, resulting in a perfectly phase linear transformation. [This type of filter is impossible in the analog domain due to the phase-shift caused by very steep roll-off filters.] See FIR, IIR. After the data have been filtered below the Nyquist frequency, the next step is decimation where the data are re-sampled to produce an output stream of 44.1kHz, with the attractive result that the excess data thereby provides increased bit-resolution. See anti-aliasing filter, reconstruction filter, DSD.

 

 

deck plate : In a tape recorder transport, the heavy metal plate on which the headstack, rollers, and other transport components are located.

 

decoding : (1) In signal processing, restoring a signal to its original state by reprocessing the signal in a complementary manner, e.g., a NR system’s re-expansion of the signal during playback. (2) In digital recording, the entire process converting the encoded data stream back into an analog signal, including the process of error correction, i.e., digital-to-analog conversion.

 

deconvolution : A mathematical process for separating two signals that have been convolved. See convolution.

 

Decoupler (Isolator): A device intended to prevent the transmission of physical vibration over a specific frequency range

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decrescendo : A musical term indicating a gradual reduction in loudness.

 

defeat switch : A control that can be used to mute a signal on a mixer.

 

definition : A qualitative term that denotes the clarity of a sound. A sound with poor definition may, like some woodwinds in their middle ranges, be easily mistaken for a similar sound. In recording, the apparent definition of a sound can be increased by boosting the frequency band characteristic to the specific sound of the instrument, and cutting other frequencies it has in common with other sounds in the mix.

 

delay : (1) The first stage of a five-stage D(elay)AD(ecay)SR envelope, which delays the beginning of the envelope’s attack segment. See ADSR.

(2) An audio effect which temporarily suppresses the beginning of a sound, producing echo, chorusing, phasing, and flanging effects. A modulated digital delay effect which varies the time and/or intensity of the delay effect over time. See double tracking.

(3) A signal processor used for flanging, chorusing, and echo, that holds its input for some period of time before passing it to the output, or the algorithm within a signal processor that creates delay. Also used in artificial reverberation systems and to provide delayed sound to certain loudspeakers in time-coherent sound reinforcement systems.

(4) See MIDI delay.

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delay line : Used to simulate an acoustic echo or reverberation. There exist both digital delay lines (DDL) and analog delay lines as well. The original delay lines were made by using tape recorders to record a signal while playing it back on the same machine. The distance between the record and reproduce heads causes a time delay; this technique is called tape delay. See tape delay.

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delay line feedback : A type of modulation which creates a series of echoes when the modulation source is boosted. The greater the amount of feedback, the more repetitions of each echoed event.

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delta modulation : In the UK, often, and more properly called delta-sigma modulation. A type of PCM which differs from most other digital encoding schemes in that the signal, after being sampled at a fast rate, is encoded as the difference between successive levels, rather than as the absolute level of each sample. Delta modulation requires a very high sampling rate, usually around 700kHz, but the digital words need for each step contain one bit, whereas conventional PCM samples at only about 45kHz but requires 14-16 bit words. The "delta" phase of delta modulation involves taking the difference of the reconstructed signal and the incoming signal to adjust the output to minimize the quantization error; the "sigma" part involves the summation of the differences to reconstruct the original signal, although there are a number of variant algorithms based on this basic theme. The reason for the popularity of delta modulation-type converters is the inherent linearity of the process. See also ADPCM.

 

delta time : See SMF.

 

delta-sigma modulation : See delta modulation.

 

demodulator : A device which recovers the audio signal from a modulated carrier waveform. Also called a detector.

See amplitude modulation and frequency modulation.

 

depth : (1) In stereophonic reproduction of music, depth refers to the perceived relative distance between the listener and the various instruments in the sonic image. (2) In a digital delay or flanger, a parameter which modulates the length of delay around the specified delay time. Because this happens in real-time, the pitch of the input signal is varied, causing the output signal to have an apparent vibrato effect. The speed of this vibrato is set by a rate control.

depth perception : See depth(1).

 

DES : Dolby-Encoded Stereo. A noise reduction system employed in the reproduction of stereo optical tracks in movie theaters.

 

desk : See mixer.

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detector : (1) See frequency modulation. (2) See level-sensing circuit.

 

detune : (1) (noun) A control that allows one oscillator to sound a slightly different pitch than another. (2) (verb) To slightly change the pitch of one oscillator relative to another, producing a fuller sound.

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DI : Direct Injection. Also called a direct box. (1) The use of some form of mechanical or electrical pick-up mechanism on an instrument for the purpose recording or amplification. DI also refers to the connection of an electronic keyboard or power amplifier feeds to a mixer. A DI consists of (usually) a small electronic box into which an instrument is plugged and the electroacoustic pick-up attached to the instrument itself. Pick-ups can be electro-magnetic, as on electric guitars, piezo devices, and also contact microphone, also called bugs. All types of pick-up have unbalanced outputs at mic-level (~-50dBu), so the DI box has to balance the signal and drive it to the mixing desk. DIs can be passive or active in the typical sense. Active DIs have some form of electronic amplification built-in; this is only a buffering amplifier, separating the instrument pick-up from the rest of the DI, yielding no significant gain. Active DIs offer better sound and playability over passive devices, but require batteries, phantom power, or some other means of powering the internal amplifier. (2) Any device used to convert unbalanced lines to balanced lines.

 

dialog normalization (DN) : There is a wide difference in the apparent loudness between different TV programs’ audio content. In DTV, with by standard is AC-3 encoded, a program producer chooses one of 31 different dialog normalization (abbreviated DN or "Dialnorm") values and this parameter is carried within the AC-3 datastream, where each step represents a 1dB change in level. The DN value is the difference in dB between the maximum level possible (0 dBFS) and the average loudness level of the program material. The smaller the difference between the maximum and program average levels, the lower the DN value is assigned. The lower the DN value, the lower the output volume of the AC-3 decoder is set in direct proportion, meaning that subjectively louder programs will be played back at lower volumes than those in which the average program level is less loud. This supposedly will obviate the user having to adjust the volume control between programs, once the audio listening level is set by the user.

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dialog track : The edited track on magnetic film containing the dialog portion of a film’s sound. Sometimes there may be a separate track for each actor in a scene, requiring the tracks to be mixed down to a single track. The "D "part of DME.

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diaphragm : The membrane part of a microphone’s capsule or cone of a loudspeaker that moves in response to sound waves or an incoming signal, respectively.

 

diatonic : A musical scale of eight notes spanning one octave, consisting of an ascending pattern of two whole-steps, a half-step, three whole-steps and another half-step. There are two types of diatonic scale in common use in western music: the diatonic major scale and the diatonic minor scale. Music which includes notes outside of the diatonic in which the piece is written is said to be chromatic.

 

 

 

 

 

 

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diatonic comma : After playing the Circle of Fifths, i.e., twelve ascending perfect fifths, followed by seven descending octaves, the pitch discrepancy between the ending note and the starting note is called the diatonic comma, or the Comma of Pythagoras. This discrepancy amounts to a little over 1%, or about one-sixth of a half-step and gives rise to various temperaments in an attempt to distribute the error as harmoniously as possible. See scale construction, syntonic comma.

 

dichotic : Dichotic generally refers to headphone listening where each ear hears a different signal, as opposed to diotic, where both ears hear the same signal. See also monotic.

 

difference tone : A tone produced by combining two tones which are not part of a harmonic series, having a frequency difference of 20Hz or greater. Any slower than 20Hz, and the difference of the two notes will be perceived as a pulse, called beating. Also called a resultant tone. Also called a Tartini tone.

 

differential amplifier : Usually one of the signal input terminals of an amplifier is connected to the chassis of the amplifier, i.e., it is grounded. The amplifier is then sensitive to the voltage difference between the input terminal and ground. However, in a differential amplifier, neither input terminal is grounded. Instead, the amplifier is sensitive to the voltage difference between the two inputs. Used in professional microphone preamplifier where a low-level signal has to go some distance, a differential amplifier cancels the hum induced by the proximity of the two input wires to a source of interference. In the UK, a differential amplifier is called an inverting amplifier. See differential input, common mode.

 

differential input : Signal input response to amplitude differences between two out-of-phase signals. Used in a balanced wiring system where the two wires carry signals that are identical, but 180° out-of-phase. The phase difference means that as a signal increases in voltage along one line, its mirror image on the other line decreases. This is useful because signals, such as hum and noise which have accumulated along a cable acting as an antenna, that are in phase are cancelled. See common mode, differential amplifier.

 

differential output : The output of an amplifier designed to provide two signals that are completely identical, but of opposite phase.

 

differentiator module : A highpass filter which can accentuate the higher-frequency harmonics and transients of a sound envelope. Compare with an integrator module.

 

diffraction : The bending of a sound wave around an obstacle and the reflection of a sound wave from an obstacle in its path are called diffraction. It is frequency dependent. Where the wavelength is short compared to the obstacle, reflection will occur as well as bending of the wave front. When the wavelength is long with respect to the obstacle, little reflection will occur and the bending will be more pronounced. See also refraction.

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digital : In audio, the opposite of analog. The representation of audio or video as a series of encoded binary amplitude values, rather than as a continuous waveform.

 

Digital Acoustics Processor : A consumer audio device that attempts to simulate the acoustics of an auditorium or other room by adding suitable time delays and synthetic reverberation to recorded signals.

 

digital audio : The application of digital technology to the recording, processing, and reproduction of music is somewhat loosely called digital audio, as opposed to analog.

 

Digital Audio Broadcasting : An alternative to AM and FM broadcasting with audio quality comparable to that of the CD, it does not suffer from fringe area fading or multipath distortion, and requires less radiated power than conventional broadcasting (1kW versus 50kW for AM and up to 100kW for FM.)

 

Digital audio extraction : See grabbing.

 

Digital Audio Mastering System : See digital multitrack.

 

Digital Audio Recorder (DAR) : Any type of audio recording system which records upon a digital medium, such as DAT or hard disk. DAT or DCC recorders, digital dubbers, digital multitracks, and hard-disk recording systems are all example of digital audio recorders. These recorders are an alternative to analog recorders, such as traditional cassette or reel-to-reel formats which do not convert the waveform to a digital representation prior to writing it to the recording medium.

 

digital black : In digital audio, a term which means complete silence. Digital black is calculated by taking the sample word length (e.g., 16, 20, or 24 bits) and multiplying this bit depth by 6dB, a number which represents the dynamic range represented by one bit. In a 16-bit system, for example, full code represents 96dB, the maximum amplitude that the system is capable of encoding without clipping. Digital black is at the opposite end of that dynamic range, or 96dB down from full code amplitude.

 

Digital Compact Cassette : A type of recording format announced by Philips in 1990, designed to compete with the R-DAT format. The system allows for the recording and playback of analog cassettes as well as DCCs on the same machine. Uses PASC (Precision Adaptive Subband Coding), derived from the MPEG-1, Layer 1 data reduction system to provide data compression (lossy) for the recording of digital audio on wide magnetic tape at ips. This format has not been widely adopted. Sometimes called DCAC for Digital Audio Compact Cassette. See also MiniDisc, DAT, and CD.

 

digital delay line (DDL) : See delay line.

 

digital dubbers : Film industry term for a multitrack digital recorder, usually having eight tracks per unit, that use removable hard drives or magneto-optical drives as the recording medium. The term is partly a misnomer because previous film sound terminology had used dubber to describe a copying device as opposed to a recording device.

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digital multitrack : A device for recording multiple channels of digital audio data at various sampling rates. Two formats have survived: the Sony/Studer DASH format and MDM machines of either ADAT or DTRS type. The first digital multitrack recorder was introduced in the late 1970s by 3M, a 32-track recorder called the Digital Audio Mastering System.

 

Digital Signal Processing DSP : The manipulation and modification of signals in the digital domain, possibly after having undergone analog-to-digital conversion.

 

Digital TeleVision (DTV) : See DTV.

 

digital time delay : See delay.

 

 

digital watermark : The solution for a piracy and duplication protection scheme developed jointly by Sony and Philips which writes copyright data encrypted within the CD/DVD etc. disc itself. This scheme would, for example, encode discs with a country code so that these discs would only play on players from the same country. This is presumably better than older forms of digital copy protection which tried various pilot tones or random number generators, failing ultimately because the results were either too audible or too easy to circumvent. In a digital watermark, the copyright data are stored as a modulation of the width of the injection-molded pits. Duplicating the watermark would require the same equipment as that which produced the disc stamper, the distribution of which is presumably tightly controlled. It is also possible to synchronize the modulation of the pit widths so that there is a visible pattern formed on the disc pit substrate itself, making an "analog" watermark (without the need for water, of course.) In addition to the watermark and country codes, identifiers for the mastering house and pressing plant, glass master number, ISRC catalog numbers, etc. can be stored. The digital watermarking technology has been called Pit Signal Processing (PSP) which works by modulating the strength of the laser used to record the digital data onto the glass master. One by-product of the watermarking process is that the EFM used to encode audio data onto the CD master allows the pits to vary in length between 3-11 units. These slight errors in length, or "jitter" result in slight timing errors which can cause a smearing of the stereo image as well as an increase in HF noise. The more rigid requirements of pit length control in watermarking should result in a significant reduction of pressing-induced jitter, just generally improving the CD production process.

 

Digital-to-analog converter : Commonly abbreviated D/A, D/A converter or DAC. A device that changes the sample words put out by a digital audio device into analog fluctuations in voltage that can be sent to a mixer, amplifier, or speaker. All digital synthesizers, samplers, and effects devices have DACs at their outputs to create audio signals, as the transducers in loudspeakers are inherently analog devices.

 

digitally controlled amplifier : See DCA.

 

digitally controlled oscillato : See DCO.

 

digitally controlled waveshape : A DCW varies the timbre of synthesized sound by modifying the harmonic content of the tone produced by a DCO. See waveform.

 

diminuendo : Synonym for decrescendo.

 

diminution : (1) The reduction of a major or perfect interval by one half-step to make a diminished interval.

(2) The appearance of a musical idea in note durations which are shorter than those used for its first appearance. The opposite of augmentation.

(3) A method ornamentation where notes of long duration are broken into a number of shorter notes, often at different pitches, e.g., a trill.

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DIN : Deutsche Institut für Normung. A German standards organization that proposed a set of connector configurations in the early 1960s. The standard MIDI connector is the 5-pin DIN where:
 

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DIN sync : See pilot tone.

 

diode : A diode is a circuit element which will pass current in one direction only, from the anode (positive) to the cathode (negative). Used to make DC from AC.

 

diotic : Literally, "with two ears." Diotic generally refers to headphone listening whereby the two ears hear the same signal, as opposed to monotic, where only one ear hears the signal. See also dichotic.

 

dip filter : A parametric equalizer with an extremely narrow Q, designed to remove noise in a small band such as that from a camera or light.

 

dipole : In loudspeaker design, a dipole radiator is a system which radiates forwards and rearwards with equal energy, but with opposite polarity. Examples of dipole radiators are electrostatic loudspeakers and planar speakers. Some cone-type speakers have dipole radiators. For a dipole radiator to have adequate low-frequency response, it must be very large to prevent the rear wave from canceling the front wave. Also, the dipole radiator must not be placed close to and parallel to a wall, working best when not near reflective surfaces.

 

direct box : See DI.

 

direct coupling : A connection between two devices that allows both DC and AC between them.

 

direct current (DC) : Current in only one direction. DC always has the same direction, from the positive to the negative terminal. Compare with AC.

 

direct field : See reverberant field.

 

direct metal mastering (DMM) : A system for cutting a metal mother on a record mastering lathe, eliminating the lacquer master and metal master steps. Release pressings made from a stamper are thus only two stems from the DMM and thus have less noise and distortion than those made by the older, five-step process. The DMM process is also used in CD mastering.

 

direct output : A recording console output taken directly after the input module and main channel fader, but before the panpot and output bus assignment switches. This output is sometimes used to avoid crosstalk that may be introduced if the signal is allowed to flow through the complete circuit.

 

direct positive : A optical (photographic) sound recording that, when processed, results in a track that can be played and edited; now obsolete.

 

direct radiator : A loudspeaker which does not have a horn between the moving element and the air is called a direct radiator. Most direct radiator-type speakers are for home use, while horn-type speakers are preferred for sound reinforcement applications. Direct radiators generally provide smoother, more uniform response, while horns are much more efficient, providing a greater output level for a given power input. Also, horns have greater directivity, which is desirable in sound reinforcement systems. See compression driver.

 

direct sound : (1) See reverberant field. See also free-field, critical distance.

(2) The sound received at the recording console from an electronic instrument when using a direct box.

 

Direct Stream Digital™ : A proprietary CD/DVD data format proposed by Sony and Philips for use in the SACD . DSD bandwidth is normally 2.844Mb per channel (64 times 44.1kHz), with optional sampling rates of 32 or 128 times 44.1kHz,yielding a slightly higher data rate than that required by 24-bit/96 kHz resolution conventional A/D-D/A systems. DSD uses a delta modulated ADC to generate a 2.8224MHz, 1-bit signal, a rate chosen as a simple multiple of the lowest common high-fidelity PCM sampling rate, 44.1kHz. The 1-bit datastream is recorded directly to disk, avoiding the decimation and oversampling stages, inherently improving the resultant audio quality, simplified error protection, and there is no need to frame the data into words. Sony claims that the sampling rate is so high that it more nearly approximates the original analog signal, allowing equalizers and other effects processors to better simulate analog effects. It is claimed that DSD can have frequency response up to 1MHz, or up to a dynamic range (within the audio bandwidth) of 120dB, equivalent to about a 20-bit resolution. A number of DSP algorithms are available which allow the optimization of either bandwidth or dynamic range. [Note that these benefits apply only to those players which support the DSD standard, as replay on any conventional CD, DVD or other digital format would require the decimation and framing steps.]

 

Direct Stream Transfer™ : Philips’ proprietary technology for lossless 2:1 data reduction in digital recordings on SACD. DST is optimized for audio-type signals, allowing sufficient storage capacity for double the old CD standard of 74 stereo minutes. By incorporating DST into the SACD standard, it is possible to store two complete 74-minute versions of audio material so as to combine a stereo DSD track, and a 6-channel surround mix, plus other data, text, graphics, and video, all on the single, high-density DASD layer.

 

direct-to-disc : A type of analog LP mastering in which a master tape is not used. The signal directly from the control console is used to cut the original acetate disc. This means a direct-to-disc recording cannot be edited, and is made live.

 

direct-to-disk : Recording digital audio data onto a hard disk for replay or editing.

 

direct-to-two-track : A method of recording in which the instruments and vocals are mixed and recorded directly onto a stereo half-track or DAT. If analog, no further changes or remixing is possible. The fidelity, edibility, and relatively low-cost of direct-to-two-track digital recording has revived the popularity of this medium for making master tapes, especially those intended for release on CDs. Also called live-to-two-track.

 

directional microphone : A microphone which does not have a spherical polar pattern, i.e., a microphone which is not omnidirectional, such as a cardioid, figure-eight, etc. having an acceptance angle of less than 360¢ª. See directivity.

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directivity : Describes the angle of coverage of a loudspeaker system or microphone acceptance angle, both in the vertical and horizontal planes. High directivity equates to a narrow angle of coverage. The directivity factor is a measure of the directionality of the sound output of a loudspeaker. See also Q.

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DirectX : The most common audio effects plug-in format used by Windows™ software.

 

discrete : Refers to a 1:1 relationship of recorded tracks on an audio medium or film print and the resulting number of speaker channels. Contrast with matrixed sound.

 

discrete 6-track : Traditionally means the five-speakers-behind-the-screen system made popular by the Todd-AO 70mm process (although first used for Cinerama). Today the term sometimes means six nonmatrixed tracks, assigned to L,C,R,LS,RS,Subwoofer. See also 5.1.

 

discrete output : A direct output from a mixer channel, which services only that one channel.

 

disk-at-once : A CD production process where the entire disc is written in one burn; the laser is never turned off. Ideal for audio, disk-at-once mode allows gaps between tracks of any length (except the first track, which must have a 2-3 second gap.) Compare with track-at-once.

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dispersion : (1) The spreading of sound waves as they leave a loudspeaker.

(2) Another term for refraction.

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displacement : The distance between some measured position of a moving object, e.g., a speaker cone, and its static position. Also applies to the position of air molecules in a sound wave. See rarefaction.

 

distant miking : The opposite of close miking. In recording, the placement of one or more microphones relatively far away from the sound source. This technique picks up a substantial portion of reverberant sound, and is therefore used to make most classical or orchestral recordings to capture the sound as closely as possible to that experienced by an audience. In the studio, close and distant mics on any instrument or group may be blended at the mixer to achieve the desired sonic image. See depth.

 

distortion : Also called correlated noise. Any (usually) unwanted sound which varies with the input signal. (1) Any undesirable change in the characteristics of an audio signal of six types: The two types of (i) nonlinear distortion are intermodulation distortion and harmonic distortion. Other types of distortion are (ii) frequency distortion (pitch-shift), (iii) phase distortion (time shift), (iv) transient distortion, (v) scale (volume) distortion, and (vi) frequency modulation distortion. There are other factors which cause music reproduction to be untrue to the original but which are not considered distortion, such as background noise, and a lack of directional realism and proper ambience due to the use of too few channels of reproduction. See noise. (2) A sound modulation technique whereby the original waveform is distorted intentionally.

 

dither : A noise-based rounding method used to add a tiny amount of controlled noise to a digital audio file to make other, more objectionable errors less obvious and/or to convert from one word size down to a smaller word, e.g., from 24-bit resolution to 16-bits. Redithering is a dithering process used in digital-to-digital signal processing to distinguish it from the dithering process used during the original A/D conversion. There are several ways to dither:

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1. Add white noise at about half or one-third the value of the LSB, or half the level that a system can transmit. Thus, for a 16-bit converter encoding a range of 2V, the LSB is equivalent to a difference of 30.5µV (2÷65,536V), yielding dithered noise of about 10-15µV;

2. Second-Order dither in which the dither signal (white noise) is processed by a highpass filter to remove low-frequency components. This makes the noise less appar-ent to the ear, since humans are less sensitive to high-frequency noise than other lev-els;

3. Noise-shaping in which the dither signal is run through a set of filters to provide the most energy in regions where the ear is the least sensitive;

4. (Triangular Probability Density Function) where before the noise is shaped, it has a different spectral content than ordinary white noise. It has better noise modulation performance, which is how the noise affects the signal itself;

5. Sony’s SBM (Super Bit-Mapping) where the audio is run through a processor with an algorithm that maps a series of higher-resolution samples to a series of lower-resolution samples;

6. The Apogee UV-22, which is not really dither. Instead, it uses a periodic signal centered around 22kHz that has good performance in terms of audibility and noise modulation. Placing the signal this high in the audio spectrum makes it very difficult to hear and produces fewer effects on the character of the signal.

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DLL : Dynamic Link Library. Files used by PC-type computer application programs to provide additional functionality to the computer’s operating system. The equivalent of an extension file on a Mac.

 

DLS : DownLoadable Samples. A standard which allows multimedia games or other programs to contain samples which would be downloaded to the playback hardware. This is a hybrid between streaming digital audio (direct audio from CD-ROM, for example) and MIDI, which alters predefined sounds. DLS is an attempt to solve the problems inherent in the ambiguity of the GM specification and the somewhat random sounds produced by the playback hardware. DLS-1 specifies: 16-zone multisampled soundbanks with 128 zones for drum banks, pitch-shifting, ADSR for amplitude and pitch, and LFO for amplitude or pitch. DLS-1 was ratified by the MMA in 1997. See DLS-2.

 

DLS-2 : Downloadable Sounds Level 2. An improvement over DLS which moves closer to enabling multitrack audio and MIDI programs to be used by audio and MIDI hardware and software interchangeably. This is accomplished by transferring entire multisampled instruments, along with the MIDI data, to the end-user’s platform, resulting in playback as the author intended. In addition to the specification of DLS-1, DLS-2 specifies: resonant filter control, adds delay and hold to envelope segments, effects routing for chorus and reverb, no limit to the number of regions in any soundbank, each reason can have independent envelope and filter data, and is extensible to include other forms of synthesis. Ratified by the MMA in early 1999. See also MPEG-4.

 

DLT : Digital Linear Tape. A tape-based computer backup format developed by Quantum Laboratories.

 

DMA : Direct Memory Access. A digital logic design which allows peripheral devices to communicate directly with the system memory, rather than requiring the central processor to stop whatever processing it was doing to control communications between an attached device (usually having some kind of I/O function) and the computer memory.

 

DME : Dialog, Music, and Effects. The three basic stems of film soundtracks, originally meant to denote the 35mm 3-track master mix of academy mono films.

 

DN : See dialog normalization.

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DNR : Dynamic Noise Reduction. Similar to Dolby, but was not effective.

Dolby Digital™ : The 5.1-channel digital format created by Dolby Laboratories, first used in 1992 for "Batman Returns." In current usage, the term applies to both the Dolby 35mm theatrical format, which contains the data printed optically between the sprocket holes, and for video formats, such as DVD, laserdisc, and DTV. AC-3, as Dolby Digital was first called, used RF modulation of the digital signal onto one of the analog tracks, making it possible to fit an entire movie, along with the already existing digital tracks, onto a conventional laserdisc; a demodulator was needed to recover the audio back into a digital bitstream. The Dolby Digital format is a surround-sound, split-band, perceptual coding scheme. AC-3 was designed as a 5.1 multichannel format , using approximately 13:1 lossy compression, and is specified as the matrixing format for DVD and DTV. Also used in HDTV broadcasts, SR-D, and DSD cinema productions. Versatile, in that parameters such as bit-rate and number of channels can be tailored to particular applications, unique in that the data bits are distributed dynamically among the filter bands as needed by the particular frequency spectrum or dynamic nature of the program. Data rates vary from 32kbps for a single mono channel to as high as 640 kbps for 5.1 format. The data rate is 320kbps for film, 384kbps for laserdisc, and 384kbps or 448kbps for DVD, although the maximum throughput for the specification is 640kbps. Dolby’s current decoder can accept incoming data at 32kHz, 44.1kHz, or 48kHz sample rates, with bit depths of 16, 18, or 20 bits. The commercial competitor to the Dolby Digital format is DTS. See metadata, audio coding mode.

 

Dolby Fax : See ISDN.

 

Dolby Motion Picture 4:2:4 : A matrixed surround-sound system which combines multichannel LCRS audio in such a way that the encoded signal forms a stereo-compatible, two-channel format for recording and broadcasting. Originally developed in 1977 for "Star Wars," and now in wide use. As with any matrix system, it is impossible to completely recover the original multichannel signals with perfect isolation. The decoder disguises this problem through a steering process which emphasizes the signal emanating from its appropriate loudspeaker by canceling out a portion of the crosstalk in adjacent channels. See also free encoding, Pro Logic.

 

Dolby noise : The Dolby SR analog allows the comparison of the recorded Dolby noise on a tape to that generated by the decoder, with four continuous seconds of noise to identify the generator, and two 2-second sections of noise indicating that the monitoring is off-tape. This allows for confirmation of correct EQ settings as well as playback verification. The broadband reference signal used to correctly calibrate the different Dolby codecs is called Dolby noise. See Dolby tone.

 

Dolby noise reduction : A type of two-ended, dynamic noise reduction for magnetic tape recording and playback. The essential difference between a compander and the Dolby system is that the Dolby system is frequency-dependent. The compander was developed to reduce distortion. Dolby applies companding to frequency variations in addition to signal amplitude variations, adjusting gain as frequency changes. The Dolby-A and Dolby-SR systems are used for professional recording in studios. Consumer tape decks use either a Dolby-B or Dolby-C system. Dolby-B operates only at high frequencies and reduces tape hiss by about 10dB. Dolby-C works over a slightly wider frequency range, providing a noise reduction of up to 20dB. All of the Dolby systems operate on quiet passages, below levels of about -10VU. Very strong signals, such as over 60dB or at frequencies below 500Hz are not affected by the Dolby system because these signals are not degraded by tape noise. When the recorded signal is played back, the Dolby circuit reduces the accentuated high-frequency signals so that the frequency response of the record/playback system is flat, hence reducing also the high-frequency tape hiss, improving the S/N ratio of the taped music. See asperity, Barkhausen effect, compander, dbxcompander,dbx, spectral recording.

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Dolby ProLogic™ : A four-channel perceptual coding scheme developed by Dolby Labs where an LCRS audio signal is converted into two channels of analog audio, then recovered to yield discrete left, center, right, and mono surround channels. This is a hardware version of their surround decoder originally developed for the Dolby Motion Picture 4:2:4 matrix surround-sound system, developed for the Star Wars picture in 1977. If a subwoofer is used, it is generally fed by lowpass-filtering a mix of the three front channels at the receiver.

 

Dolby SR.D™ : A system developed by the Dolby company for placing a digital audio soundtrack onto 35mm film, first used in 1992. The soundtrack includes a Dolby Digital mix, as well as an SR analog stereo optical track. The data are compressed and printed onto the film between the sprocket holes. See surround-sound, perceptual coding, Dolby surround-sound, spectral recording.

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Dolby SR™ : Dolby-SR is a complex type of two-ended, dynamic split-band, noise reduction compander system that outperforms Dolby-A, -B, or -C systems and also results in reduced distortion in most cases. This was developed as an upgrade to the professional Dolby-A, featuring an improvement in tracking accuracy and sliding bands, and closest to C-type noise reduction. S-Type noise reduction is the consumer analog. See SR.D.

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Dolby Stereo™ : The original Dolby Surround system which used four audio channels carried on a stereo optical track on 35mm film, using Dolby perceptual encoding. On 70mm film, six audio channels are recorded on discrete magnetic tracks laid onto the film. In the broadest and most common usage, the trademark that appears on movie prints, advertisements, and posters which means that a given film has been released in prints that employ Dolby A-Type noise reduction encoding. Beginning in 1987, Dolby-SR has been available on 35mm stereo optical prints. Dolby Stereo on 70mm usually means four discrete primary channels (LCRS) with the left-center and right-center tracks dedicated to low-frequency information (below 250 Hz). The four tracks are normally use A-Type encoding, although selected 70mm films, since 1987, have utilized Dolby-

SR encoding. See film soundtrack.

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