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Dictionary of Audio Terminology - D


D50 (%) - A linear measure of the early-to-total energy ratio expressed in percentage.

DA-88 - Tascam's model number for their digital multitrack recorder using Sony-developed "Hi8" 8mm videotape as the storage medium.

DA (distribution amplifier) - Common abbreviation used throughout the broadcast, telecommunication and sound consulting/contracting fields.

D-A (digital-analog) - The process of converting digital signals into analog signals. See: DAC.

DAA (Digital Access Arrangement) - Name for the physical connection to the telephone line known as the local loop. The DAA performs the four critical functions of line termination, isolation, hybrid, and ring detection.

DAB (digital audio broadcast) - (1) NRSC (National Radio Systems Committee) term for the next generation of digital radio broadcast. (2) Initials of the compiler of this Pro Audio Reference.

DAC (or D/A, digital-to-analog converter) - The electronic component which converts digital words into analog signals that can then be amplified and used to drive loudspeakers, etc.

damping factor - Damping is a measure of a power amplifier's ability to control the back-emf motion of the loudspeaker cone after the signal disappears. The damping factor of a system is the ratio of the loudspeaker's nominal impedance to the total impedance driving it.

Daniels, Drew - (b. 1947-2010) American "pro audio icon." [MIX magazine.]

Dansette - World's first portable record player brought out in 1952 by the British company, Margolin.

Dante™ - A trademark of Audinate for their proprietary digital audio networking technology.

dan tranh - A Vietnamese plucked string instrument.


DAR (digital audio radio) - EIA term for the next generation of digital radio broadcasting standards.

Darbuka or goblet drum - A wine glass shaped hand drum indigenous to the Middle East.

DASH (digital audio stationary head) - A family of formats for ensuring compatibility among digital multitrack studio recorders using stationary (as opposed to rotating) heads. The DASH standard, popularized by Sony and Studer, specifies 2 to 48 tracks, with tape speeds from 12 to 76 cm/sec.

DAT (digital audio tape recorder) - A digital audio recorder utilizing a magnetic tape cassette system with rotary heads similar to that of a video recorder.

data compression or digital audio data compression - Any of several algorithms designed to reduce the number of bits (hence, bandwidth and storage requirements) required for accurate digital audio storage and transmission. Characterized by being "lossless" or "lossy." The audio compression is "lossy" if actual data is lost due to the compression scheme, and "lossless" if it is not. Well-designed algorithms ensure "lost" information is inaudible.

data converter bits - The number of bits determines the data converter precision. The more bits available, the more precise the conversion, i.e., the closer the digital answer will be to the analog original.

DAW (digital audio workstation) - Any of several software/hardware systems using a computer as the basis for creating, editing, storing, and playback of digital audio, using the computer's hard disk as the recording medium, or a SAN.

DB-9 connector - (Note: the correct term is DE-9 but has lost out to this popular misusage. DE is the shell size for a 9-pin connector; DB is the shell size for a 25-pin connector.) A smaller 9-pin version of the connector used for RS-232 communications. [Newton])

DB-25 connector - A 25-pin D-shell connector originally standardized for RS-232 serial communications.

dB (decibel) - (1) A measuring system first used in telephony (Martin, W.H., "DeciBel -- the new name for the transmission unit. Bell System Tech. J. January, 1929), where signal loss is a logarithmic function of the cable length. (2) The preferred method and term for representing the ratio of different audio levels. It is a mathematical shorthand that uses logarithms (a shortcut using the powers of 10 to represent the actual number) to reduce the size of the number. For example, instead of saying the dynamic range is 32,000 to 1, we say it is 90 dB [the answer in dB equals 20 log x/y, where x and y are the different signal levels]. Being a ratio, decibels have no units. Everything is relative. Since it is relative, then it must be relative to some 0 dB reference point. To distinguish between reference points a suffix letter is added as follows [The officially correct way per AES-R2, IEC 60027-3 & IEC 60268-2 documents is to enclose the reference value in parenthesis separated by a space from "dB".]

dBA - Unofficial but popular way of stating loudness measurements made using an A-weighting curve, originally referenced to a loudness level of 40 phons.

dBC - Unofficial but popular way of stating loudness measurements made using a C-weighting curve, originally referenced to a loudness level of 100 phons.

dB drag racer - Term applied to auto sound enthusiasts that travel the world to compete in loudness contests. Current record is over 177 dB-SPL.

DC or direct current - An electric current that flows in one direction.

DC-300 - One of the most famous power amplifiers ever was the Crown DC-300. Designed and first manufactured in 1967 by Gerald Stanley, Crown's ace engineer, it was named from its design being direct-coupled to allow for direct current operation and having 300 watts of stereo 8-ohm power.

DCA (digitally-controlled attenuator) - Also digitally-controlled analog and digitally-controlled amplifier.

DCC (Digital Compact Cassette) - Philips's digital version of the standard analog cassette tape system. A DCC recorder plays and records digital cassettes, as well as playing analog cassettes.

DCE (Data Communications Equipment) - Within the RS-232 standard, the equipment that provides the functions required to establish, maintain, and terminate a connection, as well as the signal conversion, and coding required for communication between data terminal equipment and data circuit.

DC offset - The amount of extra input voltage required to produce exactly zero output voltage with no applied signal.

DDD (Dick's dipole driver) or DDD Bending Wave Converter - At first glance the German Physiks DDD driver looks like a conventional piston cone driver. It has a voice coil/magnet assembly that serves as the actuator and it has a cone, though this is longer and narrower than usual. The shape is where the similarity with a piston driver ends. With a piston driver when the voice coil moves, the entire cone moves together with it – or that is what we want it to do. This is why the cone and voice coil structure is made as rigid as possible. The sound wave that a piston driver produces moves in the same direction as the movement of the cone. [from website]

DE-9 connector - The correct term for DB-9 is DE-9 but has lost out to the popular misusage of DB-9. DE is the shell size for a 9-pin connector.

decade - A tenfold increase or decrease in any quantity.

decay - A gradual magnitude decrease of signal level, occurring immediately after a signal reaches its peak.

Decca tree - A microphone technique developed by Decca Records in the early '50s that uses three omnidirectional microphones spaced in a triangular pattern aimed at the source. Two of the microphones are spaced far enough apart that the third microphone provides a center fill function.

decibel Abbr. dB - Equal to one-tenth of a bel. [After Alexander Graham Bell.] (1) A measuring system first used in telephony (Martin, W.H., "DeciBel -- the new name for the transmission unit. Bell System Tech. J. January, 1929), where signal loss is a logarithmic function of the cable length. (2) The preferred method and term for representing the ratio of different audio levels. It is a mathematical shorthand that uses logarithms (a shortcut using the powers of 10 to represent the actual number) to reduce the size of the number. For example, instead of saying the dynamic range is 32,000 to 1, we say it is 90 dB [the answer in dB equals 20 log x/y, where x and y are the different signal levels]. Being a ratio, decibels have no units. Everything is relative. Since it is relative, then it must be relative to some 0 dB reference point. To distinguish between reference points a suffix letter is added as follows [The officially correct way per AES-R2, IEC 60027-3 & IEC 60268-2 documents is to enclose the reference value in parenthesis separated by a space from "dB".

0 dBu Preferred informal abbreviation for the official dB (0.775 V); a voltage reference point equal to 0.775 Vrms. [This reference originally was labeled dBv (lower-case) but was too often confused with dBV (upper-case), so it was changed to dBu (for unterminated).]

+4 dBu - Standard pro audio voltage reference level equal to 1.23 Vrms.

0 dBV - Preferred informal abbreviation for the official dB (1.0 V); a voltage reference point equal to 1.0 Vrms.

-10 dBV - Standard voltage reference level for consumer and some pro audio use (e.g. TASCAM), equal to 0.316 Vrms. (Tip: RCA connectors are a good indicator of units operating at -10 dBV levels.)

0 dBm - Preferred informal abbreviation of the official dB (mW); a power reference point equal to 1 milliwatt. To convert into an equivalent voltage level, the impedance must be specified. For example, 0 dBm into 600 ohms gives an equivalent voltage level of 0.775 V, or 0 dBu (see above); however, 0 dBm into 50 ohms, for instance, yields an equivalent voltage of 0.224 V -- something quite different. Since modern audio engineering is concerned with voltage levels, as opposed to power levels of yore, the convention of using a reference level of 0 dBm is obsolete. The reference levels of +4 dBu, or -10 dBV are the preferred units.

0 dBr - An arbitrary reference level (r = re; or reference) that must be specified. For example, a signal-to-noise graph may be calibrated in dBr, where 0 dBr is specified to be equal to 1.23 Vrms (+4 dBu); commonly stated as "dB re +4," that is, "0 dBr is defined to be equal to +4 dBu."

0 dBFS - A digital audio reference level equal to "Full Scale." Used in specifying A/D and D/A audio data converters. Full scale refers to the maximum peak voltage level possible before "digital clipping," or digital overload (see overs) of the data converter. The Full Scale value is fixed by the internal data converter design, and varies from model to model.

0 dBf Preferred informal abbreviation of the official dB (fW); a power reference point equal to 1 femtowatt, i.e., 10-15 watts.

0 dB-SPL - The reference point for the threshold of hearing, equal to 20 microPA (micro Pascals rms). [Note: dB-SPL is defined differently for gases and everything else. Per ANSI S1.1-1994, for gases, the reference level is 20 microPA, but for sound in media other than gases, unless otherwise specified, the reference is 1 microPA.]

Since 1 PA = 1 newton/m2 = .000145 PSI (pounds per square inch). Then 0 dB-SPL = ±2.9 nano PSI (rms) change in the ambient pressure. Also therefore, it is a change in 1 atm ambient pressure of ± 1 atm (±14.7 PSI) that is equivalent to a loudness level of 194 dB-SPL, i.e., equals 2 atm on the overpressure portion of the cycle and 0 atm on the underpressure portion. And higher positive pressures are called shock waves, not sound.

dBA - Unofficial but popular way of stating loudness measurements made using an A-weighting curve, originally referenced to a loudness level of 40 phons.

dBC - Unofficial but popular way of stating loudness measurements made using a C-weighting curve, originally referenced to a loudness level of 100 phons.

dBPa - Preferred informal abbreviation of the official dB (Pa); a reference point equal to 1 Pascal.

Decibel Festival - "International festival of electronic music performance, visual art and new media." Held in Seattle each summer after Bumbershoot. decimal digit - Everyday normal, base-10 numbers.

deck - Popular DJ jargon for turntables and sometimes CD players.

decoupling capacitor or bypass capacitor - A capacitor connected from (usually) power supply lines to ground, for the purposes of diverting AC ripple voltages and currents to ground in order to keep the DC supple lines clean and quiet.

DED (pronounced "dead") (dark emitting diode) - A variation of LED technology used exclusively by the CIA for clandestine equipment. Also popular as power-off indicators.

de-emphasis - In telecommunication, de-emphasis is the complement of pre-emphasis, in the antinoise system called emphasis. Emphasis is a system process designed to decrease, (within a band of frequencies), the magnitude of some (usually higher) frequencies with respect to the magnitude of other (usually lower) frequencies in order to improve the overall signal-to-noise ratio by minimizing the adverse effects of such phenomena as attenuation differences or saturation of recording media in subsequent parts of the system. [Wikipedia]

de-esser - A special type of audio signal compressor that operates only at high frequencies (>3 kHz), used to reduce the effect of vocal sibilant sounds.

DFD (difference frequency distortion) - A distortion measurement test which specifies two equal-amplitude closely spaced high frequency signals. Common test tones are 19 kHz and 20 kHz for full audio bandwidth units. While all combinations of IM distortion products are possible, this test usually measures only the low-frequency second-order product falling at f2-f1, i.e., at 1 kHz. The principal standard is IEC 60268-3.

De Forest, Lee (b. 1873-1961) Known as "the Father of Radio," he was an American electrical engineer who patented the triode electron tube (1907) that made possible the amplification and detection of radio waves. He originated radio news broadcasts in 1916. [AHD]

degree - (1) In reference to physics, a unit division of a temperature scale. (2) In reference to mathematics, a planar unit of angular measure equal in magnitude to 1/360 of a complete revolution. (3) In reference to cartography, a unit of latitude or longitude, equal to 1/360 of a great circle. [AHD]

delay - (1) Crossovers. A signal processing device or circuit used to delay one or more of the output signals by a controllable amount. This feature is used to correct for loudspeaker drivers that are mounted such that their points of apparent sound origin (not necessarily their voice coils) are not physically aligned. Good delay circuits are frequency independent, meaning the specified delay is equal for all audio frequencies (constant group delay). Delay circuits based on digital sampling techniques are inherently frequency independent and thus preferred. (2) In reference to MI, digital audio delay circuits comprise the heart of most all "effects" boxes sold in the musical instrument world. Reverb, flanging, chorusing, phasers, echoing, looping, etc., all use delay in one form or another. (3) In reference to sound reinforcement, acousticians and sound contractors use signal delay units to "aim" loudspeaker arrays. Introducing small amounts of delay between identical, closely-mounted drivers, fed from the same source, controls the direction of the combined response.

delay skew -The time arrival difference between received signals at the far end. For example, the maximum allowed in CAT 5e wiring is 45 ns.

delta modulation - A single-bit coding technique in which a constant step size digitizes the input waveform. Past knowledge of the information permits encoding only the differences between consecutive values.

delta-sigma (Δ-Σ) ADC or delta-sigma modulation - An analog-to-digital conversion scheme rooted in a design originally proposed in 1946, but not made practical until 1974 by James C. Candy.

delta-sigma modulation (also sigma-delta) Symbol Δ-Σ; An analog-to-digital conversion scheme rooted in a design originally proposed in 1946, but not made practical until 1974 by James C. Candy. Inose and Yasuda coined the name delta-sigma modulation at the University of Tokyo in 1962, but due to a misunderstanding the words were interchanged and taken to be sigma-delta. Both names are still used for describing this modulator. Characterized by oversampling and digital filtering to achieve high performance at low cost, a delta-sigma A/D thus consists of an analog modulator and a digital filter. The fundamental principle behind the modulator is that of a single-bit A/D converter embedded in an analog negative feedback loop with high open loop gain. The modulator loop oversamples and processes the analog input at a rate much higher than the bandwidth of interest. The modulator's output provides 1-bit information at a very high rate and in a format that a digital filter can process to extract higher resolution (such as 20-bits) at a lower rate.

dempo - "In music, taking a song or a part of a song down tempo, or slower." [Pseudodictionary.com]

denominator - The bottom part of a common fraction (numerator/denominator).

dereverberation - Reverberation reduction; alternative term for room correction (or compensation or equalization -- exchangeable terms). All use advanced DSP methods to improve room acoustics.

Descartes, René (b. 1596-1650) French mathematician and philosopher. Considered the father of analytic geometry, he formulated the Cartesian system of coordinates.

deserializer - A serial-to-parallel data converter; used in buses and networks.

destructive solo - refers to certain console designs where it replaces the main mix with the soloed channel.

device driver - The final software interface between high-level programs and the driven hardware.

DI (digital audio input) - AES3 (& IEC 60958-4) abbreviation to be used for panel marking where space is limited and the function of the XLR AES3 connector might be confused with an analog signal connector.

DI (direct input) box - Also known as a DI box, a phrase first coined by Franklin J. Miller, founder of Sescom, to describe a device that enables a musical instrument (guitar, etc.) to be connected directly to a mic- or line-level mixer input. The box provides the very high input impedance required by the instrument and puts out the correct level for the mixer.

diatonic - Of or using only the eight tones of a standard major or minor scale without chromatic deviations. [AHD] DICE™ (Digital Interface Communications Engine) - Trademark created originally by TC Electronic, now used by TC Applied Technologies Ltd. for their IEEE-1394, AES3, et al., transceiver single chip integrated circuit.

dichotic - Pertaining to different sounds present at both ears.

dichotic listening - Listening to a different message in each ear at the same time.

Dickinson, Jim - (b. 1941-2009) American musician/producer who became a great cult hero to many musicians including Bob Dylan.

Diddley Bow (also seen as Diddlie Bow) - A one-string guitar made by stretching a string between two nails in a door.

dielectric - A nonconductor of electricity, especially a substance with electrical conductivity of less than a millionth (10-6) of a siemens. [AHD]

dielectric constant - A measure of the ability of a material to resist the formation of an electric field within it.

difference frequency distortion (DFD) - ITU-R (old CCIF), Twin-Tone, or Difference-Tone IMD - All these terms refer to the same test and are used interchangeably. The test specifies two equal-amplitude closely spaced high frequency signals. Common test tones are 19 kHz and 20 kHz for full audio bandwidth units. While all combinations of IM distortion products are possible, this test usually measures only the low-frequency second-order product falling at f2-f1, i.e., at 1 kHz. The principal standard is IEC 60268-3.

difference-tone IMD - ITU-R (old CCIF), Twin-Tone, or Difference Frequency Distortion (DFD) - All these terms refer to the same test and are used interchangeably. The test specifies two equal-amplitude closely spaced high frequency signals. Common test tones are 19 kHz and 20 kHz for full audio bandwidth units. While all combinations of IM distortion products are possible, this test usually measures only the low-frequency second-order product falling at f2-f1, i.e., at 1 kHz. The principal standard is IEC 60268-3.

differential amplifier - A three-terminal analog device consisting of two inputs designated positive and negative and one output that responds to the difference in potential between them.

differential crosstalk - In reference to printed circuit boards, the electromagnetic coupling possible between two adjacent differential traces and other near-by traces. The differential traces are theoretically immune to common mode coupling but can induce noise into neighboring traces.

diffraction - The bending of waves around obstacles and the spreading of waves through openings that are approximately the same as the wavelength of the waves. See link.

diffraction grating - A usually glass or polished metal surface having a large number of very fine parallel grooves or slits cut in the surface and used to produce optical spectra by diffraction of reflected or transmitted light. [AHD]

diffuse - Widely spread out or scattered; not concentrated. [AHD]

diffuse sound - A sound field without directionality; random sound.

diffuser (or diffusor, British spelling; in acoustics, the British spelling is seen most often.) - A commercial device that diffuses, or scatters sound.

digital audio - The use of sampling and quantization techniques to store or transmit audio information in binary form. The use of numbers (typically binary) to represent audio signals.

digital audio data compression - Commonly shortened to "audio compression." Any of several algorithms designed to reduce the number of bits (hence, bandwidth and storage requirements) required for accurate digital audio storage and transmission. Characterized by being "lossless" or "lossy." The audio compression is "lossy" if actual data is lost due to the compression scheme, and "lossless" if it is not.

digital audio watermarking - Embedded data code within the digitized audio or video image that can be recovered but which will not affect the quality of the product. Various methods exist, but all consist of very short (2-5 microseconds long) pieces of code containing all the relevant data about the copyright owner and performance royalties. All make use of the science of steganography.

digital clipping - Digital overload of the data converter.

digital filter - Any filter accomplished in the digital domain.

digital hybrid - In reference to telecommunications - A term used to describe an interface box that converts a conversation (or data signal) coming in on two pairs (one pair for each direction of the conversation or signal) onto one pair and vice versa (i.e., a 2-wire to 4-wire converter). This is necessary because all long distance circuits are two pairs, while most local circuits are one pair. The name comes from the original use of a "hybrid coil" in the telephone whose function was to keep the send and receive signals separated. Both analog and digital hybrid designs are found. A fundamental (and unavoidable) problem in any 2-wire to 4-wire design is leakage (crosstalk) between the transmit and receive signals. In analog designs leakage is reduced by modeling the impedance seen by the transmit amplifier as it drives the hybrid coil. Because telephone-line impedance is complex and not well modeled by a simple passive RLC circuit, only 10 dB to 15 dB of leakage reduction is usually possible. Digital hybrids use DSP technology to model and dynamically adapt to provide much greater reduction than analog designs, typically resulting in reductions of 30 dB to 40 dB. However, the best digital hybrids incorporate acoustic echo cancelling (AEC) circuitry to gain even greater improvements. The AEC works to cancel out any remaining signal coming from the loudspeaker (far-end received signal) from the microphone signal before they can be retransmitted to the far end as acoustic echo. Digital hybrids with AEC achieve total leakage reduction of 50 dB to 65 dB.

digital overs - A term associated with A/D converters used to describe input signals exceeding the full scale range (0 dBFS). Overs indicators vary from simple single LEDs to elaborate calibrated digital meters. To be of genuine value the overs indicator, however displayed, must be based on reading the true digital code associated with the input level. It is important to distinguish between 0 dBFS and overs; they are not the same. 0 dBFS is the absolute highest voltage level that any particular A/D can convert. It produces the equivalent of a digital code consisting of all 1s. No digital level can exceed 0 dBFS. A 0 dBFS voltage level and all levels greater than this produce the same output code of all 1s. A true overs indicator actually counts the number of times that the 0 dBFS level was exceeded and displays this number. As yet there is no standard as to how many samples exceeding 0 dBFS constitutes an over.

digital signal - Any signal which is quantized (i.e., limited to a distinct set of values) into digital words at discrete points in time. The accuracy of a digital value is dependent on the number of bits used to represent it.

digitization - Any conversion of analog information into a digital form.

diminished fifth - A fifth is an interval of 3:2 (interval is the ratio of frequencies between a base note and another note). A diminished fifth is a half step lower.

din - A jumble of loud, usually discordant sounds. [AHD]

DIN - Acronym for Deutsche Industrie Norm (Deutsches Institut fuer Normung), the German standardization body.

diode - A two-terminal device consisting of a cathode and anode that conducts only in one direction of polarity.

diotic - Pertaining to the identical sound present at both ears. Contrast with dichotic.

dipless crossfader - A crossfader design that does not attenuate the first audio signal until the fader is moved past the 50% travel point, while simultaneously increasing the second audio signal to 100% at the center point. With this design there is no attenuation (dip) in the center position for either audio signal, hence "dipless."

dipole bass or dipole subwoofer system - Literally "two poles," the name derives from the physics definition: "A pair of electric charges or magnetic poles, of equal magnitude but of opposite sign or polarity, separated by a small distance." [AHD]

direct box - Also known as a DI box, a phrase first coined by Franklin J. Miller, founder of Sescom, to describe a device that enables a musical instrument (guitar, etc.) to be connected directly to a mic- or line-level mixer input. The box provides the very high input impedance required by the instrument and puts out the correct level for the mixer. direct current Abbr. DC or dc - An electric current that flows in one direction.

directional microphone One whose response is more sensitive to sound arriving from one direction than another. See unidirectional microphone.

directivity - In reference to loudspeakers, the ratio, expressed in dB, of the on-axis sound power to the overall power output of the loudspeaker at a particular frequency.

direct out Term for auxiliary outputs found on some mic preamps, mixing consoles, and teleconferencing equipment. Direct outputs are taken before any signal processing (other than normal mic preamp functions like gain, buffering, phantom power, bandlimiting filters, etc.), or mixing with other channels is done, hence, normally at line-level.

direct sound - Sound first arriving. Sound reaching the listening location without reflections, i.e., sound that travels directly to the listener.

disc - The term used for any optical storage media.

disc jockey Abbr. DJ - "In 1935, American commentator Walter Winchell coined the term "disc jockey" (the combination of "disc" (referring to the disc records) and "jockey" (which is an operator of a machine) as a description of radio announcer Martin Block, the first announcer to become a star. The world's first woman disc jockey is said to be Yvonne Daniels (daughter of jazz singer Billy Daniels) who spun jazz records in Chicago beginning in 1964.” [Wikipedia]

disco - From French, discothèque meaning a record library.

discothèque - The first disco dance club is said to be the Scotch Club in Aachen, Germany with the first disco DJ being Heinrich (real name: Klaus Quirini) who started it all in October 1959.

discoidal capacitor - Also known as feed-thru capacitors, they are used mainly by connector designers to create in-line EMI/RFI filters for each pin. Constructed of ceramic dielectric, and toroidal shaped, these capacitors help suppress electromagnetic interference by shunting the interference to ground, and if combined with a series inductor become even more effective. The feed-thru design results in greatly reduced self-inductance compared to standard leaded capacitors. The combination of low inductance and high input/output isolation provides excellent shunting of EMI for frequencies up to and beyond 1 GHz.

discordant - Disagreeable in sound; harsh or dissonant. [AHD]

discrete - Constituting a separate thing; distinct, or a set of distinct things. [AHD]

discrete Fourier transform (DFT) - (1) A numerical method of calculating the coefficients of the Fourier series from a sampled periodic signal. (2) A DSP algorithm used to determine the Fourier coefficient corresponding to a set of frequencies, normally linearly spaced.

disk - The term used for any magnetic storage media such as computer diskettes or hard disks. From Greek diskos, the term refers primarily to non-audio digital data storage, but the advent of hard disk digital audio recording systems fogs this up somewhat.

Disklavier - Yamaha's family of reproducing ("player") pianos.

distance learning - A specialized form of videoconferencing optimized for educational uses. Distance learning allows students to attend classes in a location distant from where the course is being presented. Two-way audio and video allows student and instructor interaction.

distortion - By its name you know it is a measure of unwanted signals. Distortion is the name given to anything that alters a pure input signal in any way other than changing its size. The most common forms of distortion are unwanted components or artifacts added to the original signal, including random and hum-related noise. Distortion measures a system's linearity -- or nonlinearity, whichever way you want to look at it. Anything unwanted added to the input signal changes its shape (skews, flattens, spikes, alters symmetry or asymmetry, even if these changes are microscopic, they are there). A spectral analysis of the output shows these unwanted components.

Distributed Mode Loudspeakers (DML) - Flat panel loudspeaker innovations based on the bending wave principal. Its simplest form consists of a small driver and a large thin panel. The driver coil excites the panel but due to the large flat surface, it does not move in and out but rather "bends"- that is, deforms in a bending wave. This wave travels throughout the panel provoking 360-degree radiation of sound in the process. Careful and complex design of the rigidity of the thin flexible panel allows it to increase from the middle to the edges at an equal ratio. This allows one panel to control most of the audio range, thus eliminating multiple drivers and crossover networks.

distribution amplifier - A splitter with added features. Distribution amplifiers (usually) feature balanced inputs and outputs with high-current line drivers (often cross-coupled) capable of driving very long lines.

dither - The noise (analog or digital) added to a signal prior to quantization (or word length reduction) which reduces the distortion and noise modulation resulting from the quantization process. Although there is a slight increase in the noise level, spectrally shaped dither can minimize the apparent increase. The noise is less objectionable than the distortion, and allows low-level signals to be heard more clearly. The most popular type of dither is called TPDF.

diversity antenna - Name for popular FM receiving system for automobiles (primarily) using two antennas located in different locations (typically one in the front and rear windshields) operating in parallel, configured such that the one receiving the strongest signal at any moment dominates, greatly reducing the effects of multipath.

DIY - Acronym for do-it-yourself, usually referring to various hobbies, especially audio-related.

DJ (disc jockey) - "In 1935, American commentator Walter Winchell coined the term "disc jockey" (the combination of "disc" (referring to the disc records) and "jockey" (which is an operator of a machine) as a description of radio announcer Martin Block, the first announcer to become a star. The world's first woman disc jockey is said to be Yvonne Daniels (daughter of jazz singer Billy Daniels) who spun jazz records in Chicago beginning in 1964. [Wikipedia]

djembes (pronounced "jem-bay") - A goblet shaped hand drum that is the most popular African drum.

DLP (digital light processing) - Texas Instrument's proprietary projection display technology. The basis of the technology is the Digital Micromirror Device (DMD) semiconductor chip, which uses an array of up to 1.3 million hinged, microscopic mirrors (made using nano-technology) that operate as optical switches to create a high resolution color image.

DMD (digital micromirror device) - The basis of the DLP technology is the Digital Micromirror Device (DMD) semiconductor chip, which uses an array of up to 1.3 million hinged, microscopic mirrors (made using nano-technology) that operate as optical switches to create a high resolution color image.

DML (Distributed Mode Loudspeakers) - Flat panel loudspeaker innovations based on the bending wave principal. Its simplest form consists of a small driver and a large thin panel. The driver coil excites the panel but due to the large flat surface, it does not move in and out but rather "bends"- that is, deforms in a bending wave. This wave travels throughout the panel provoking 360-degree radiation of sound in the process -- very different from the way a conventional loudspeaker cone produces sound by "pushing" air. Careful and complex design of the rigidity of the thin flexible panel allows it to increase from the middle to the edges at an equal ratio. This allows one panel to control most of the audio range, thus eliminating multiple drivers and crossover networks.

DMM - Digital Multimeter.

do - The first tone of the diatonic scale in solfeggio. [AHD]

DO (digital audio output) - AES3 (and IEC 60958-4) abbreviation to be used for panel marking where space is limited and the function of the XLR digital AES3 connector might be confused with an analog signal connector.

Dobro® (Dopyera brothers) - A registered trademark of the Gibson Guitar Corporation, the name originated from the contraction of "Dopyera brothers" who founded their company, the Dobro Manufacturing Company, in 1928. Usually refers to a resonator guitar but does appear on other musical instruments.

Dolby Digital® - Dolby's name for its format for the digital soundtrack system for motion picture playback.

dongle - Security device for protected software: a small hardware device that, when plugged into a computer, enables a specific copy-protected program to run, the program being disabled on that computer if the device is not present. The device is effective against software piracy.

Doolittle, Thomas - Connecticut brass mill worker who, in 1877, developed the process for hard drawn copper wire in the Naugatuck Valley. He had soft, annealed copper wire drawn through a series of dies in order to increase its tensile strength. The hard drawn copper wire was strong enough for overhead wires and copper replaced iron for the telephone market.

Doppler effect - [After Christian Johann Doppler, b. 1803-1853, Austrian physicist and mathematician who first enunciated this principle in 1842.] For an observer, the apparent change in pitch (frequency) of a sound (or any wave) when there is relative motion between the source and the listener (or observer). The classic example is the train phenomenon where the pitch of the whistle sounds higher approaching and lower leaving.

DOS (pronounced "doss") (disk operating system) - A software program controlling data in memory, disk storage, running programs and I/O management.

double - In reference to music, tuned an octave lower than (from the fact that a string or pipe that is twice the length of another gives a pitch an octave lower).

double balanced - Quad mic cable or Star-quad mic cable [a term coined by Canare for the first quad mic cable, but was not trademarked and is now a generic term]. A four-conductor cable exhibiting very low noise and hum pickup (hum reduction can be 30 dB better than standard mic cable). The four conductors are wound together in a spiral, and then opposite conductors are joined together at the connectors forming a two-conductor balanced line with superior performance.

double-barreled shotgun - Harmonica that can be played from both sides. [Decharne]

double bass - A large viola that plays one octave lower than the cello, thereby doubling the bass.

double-blind comparator - A system controller for audio component comparison testing where the listener hears sound-A, sound-B, and sound-X. The listener must make a determination as to whether X is A or B. The subject may go back to A and B as often and for as long as necessary to make a determination. The listener knows that A and B are different and that X is either A or B, so there is always a correct answer. The "double-blind" part comes from neither the tester nor the listener (can be the same) knows what source is A, B or X, only the controller knows, which is downloaded after the test is complete to determine the results. First invented in 1977 by Arnold Krueger and Bern Muller (of the famous Southeastern Michigan Woofer and Tweeter Marching Society or SMWTMS), later refined and marketed by David Clark and his ABX Company. [For complete details see David L. Clark, "High-Resolution Subjective Testing Using a Double-Blind Comparator", J. Audio Eng. Soc., Vol. 30 No. 5, May 1982, pp. 330-338.]

Double MS or MSM (mid-side-mid) - An extension of the M-S microphone technique using two coincident M-S pairs sharing the same side-facing figure-of-eight microphone, one pairing for the Front L and R and the other pairing for the surrounds Ls and Rs (from Mike Skeet's article "MSM Mic Surround Technique," Audio Media, May 2003, pp. 58-59.

double precision - The use of two computer words to represent each number. This preserves or improves the precision, or correctness, of the calculated answer. For example, if the number 999 is single precision, then 999999 is the double precision equivalent.

double refraction or birefringence - The resolution or splitting of a light wave into two unequally reflected or transmitted waves by an optically anisotropic medium such as calcite or quartz.

doubling - An effect where the original signal is added to a slightly delayed version of itself. The result is a fuller sound, giving the aural impression of more players or singers then originally recorded.

Doumbek or goblet drum (aka Chalice drum or Darbuka) - A wine glass shaped hand drum indigenous to the Middle East.

downbeat - (1) The downward stroke made by a conductor to indicate the first beat of a measure. (2) The first beat of a measure. [AHD] Contrast with upbeat.

Downcut - Chopping off the end of a story or sound bite. [KU Input-Output Glossary]

downstage - The front of the stage closest to the audience, as opposed to upstage.

downward expander - Modern expander usually operating only below a set threshold point (as opposed to the center hinge point), i.e., they operate only on low-level audio.

Drag and Drop - A protocol where objects from one desktop application can be 'dragged' out of that application, through clicking on the object with a mouse, across the desktop and 'dropped' on another application. Most graphics operating systems use some form of Drag and Drop. [Newton]

DRACULA (Dynamic Range Audio Controller with Unobtrusive Level Adjustment) - BBC System for reducing the dynamic range of musical sources for AM and FM broadcasts.

drain wire - A non-insulated wire in contact with parts of a cable, usually the shield(s), used for chassis or earth grounding; in general, a ground or shield wire.

driver - In reference to computer engineering, the final software interface between high-level programs and the driven hardware.

DRM (Digital Rights Management) - Controlling mechanisms for exchanging intellectual property in digital form over the Internet or other electronic media. Basically, DRM is an encryption distribution scheme with built-in payment methods. Content is encoded, and to decode it a user must do something like supply a credit card, or provide an e-mail address, or whatever. Content owners set the conditions.

dropout - An error condition in which bits are incorrect or lost from a digital medium. Also occurs with analog tape (audio or video).

dry - In reference to recording, (1) The original recorded signal before any effects processing. (2) Any signal without reverberation; dead. Contrast with wet.

dry circuit - In reference to telephony, a circuit where voice signals are transmitted but does not carry direct current.

dry transformer - An analog audio transformer designed for AC operation only; no direct current (DC) is allowed to flow in the primary or secondary coils. Derived from the term, dry circuit, referring to a circuit where voice signals are transmitted but does not carry direct current.

DSD® (Direct Stream Digital®) - Joint trademark of Sony and Philips for their proposal for the next generation CD-standard. Sony and Philips have split from the DVD ranks to jointly propose their own solution comprised of a 1-bit, 64-times oversampled direct-stream digital SACD format. The original SACD proposal was for a hybrid disc comprising two layers: a high density (HD) DSD layer in the middle, and a standard density CD layer at the bottom. The two layers are read from the same side of the disc; the CD laser reads the bottom reflective layer through the semi-transmissive HD layer, while the middle layer is read by the HD laser delivering high-quality, multichannel sound without sacrificing backward compatibility. The HD layer has three tracks: the innermost is for two-channel stereo; the middle is a six-channel mix; and the outer is for such additional information as liner notes, still images and video clips. Maximum playing time is 74 minutes. This proposal turned out to be too expensive, so the SACD first release is a single-layer SACD-only disc.

DSP (digital signal processing) - A technology for signal processing that combines algorithms and fast number-crunching digital hardware, and is capable of high-performance and flexibility.

DSX (dynamic surround expansion) - Trademark of Audyssey Labs for their DSP algorithm that derives a left- and right-wide, height and back-surround channels to create a 10.1 surround system.

DTA (digital transducer array) - A type of direct digital loudspeaker.

D-taper or log taper - Often used as an audio taper since its 50% rotation point has 10% resistance.

DTE (Data Terminal Equipment) (1) Within the RS-232 standard, the equipment comprising the data source, the receiver, or both -- e.g., personal computers or terminals. (2) CobraNet refers to DTEs as the source and sink devices on the network, i.e., they source and sink audio.

DTMF (dual tone multi-frequency) - Normal everyday pushbutton touch-tone dialing system, where a combination of two tones is used for each button pushed.

DTRSTM (digital tape recording system) - Tascam's suggested term for describing their DA-88 type digital multitrack recorders.

DTS Coherent AcousticsT (now DTS Cinema) - A competing digital soundtrack system for motion picture playback developed by Digital Theater Systems Inc. (backed by Stephen Spielberg and Universal Studios). Its novelties are: (1) not requiring a special projector to read digital code off the filmstrip like its competitors; (2) using only very moderate compression (3:1 verses Dolby's 11:1); and (3) offering 20-bit audio. The discrete digital full bandwidth six (6) channel sound is contained on a CD that is played synchronously with the film. The synching time code is printed between the standard optical soundtrack and the picture.

DTS-ES (DTS Extended Surround) Digital Theater System's version of THX Surround EX - DTS-ES adds a third surround channel to the left and right surround channels in a DTS-encoded signal. Two versions exist: straight "DTS-ES" matrix-encodes the third surround channel into the existing left and right surround signals in a 5.1 channel source, while "DTS-ES Discrete" is a new format that adds a separate third surround channel.

DTS Zeta DigitalT (now DTS Consumer) - Digital Theater Systems' audio compression scheme applied to laserdisc, DVD and CD technology for home theater use. Competing format with Dolby's AC-3 algorithm.

duality - (1) The quality or character of being twofold; dichotomy. [AHD] (2) In reference to physics, the wave-particle theory of light is a duality. (2) In reference to electronics, the theory of duality as applied to electronic-pairs says that if every electrical term in a true statement is replaced by its dual, then the result is another true statement.

dubbing - (1) (a) To transfer (recorded material) onto a new recording medium. (b) To copy (a record or tape). (2) To insert a new soundtrack, often a synchronized translation of the original dialogue, into (a film). (3) To add (sound) into a film or tape: dub in strings behind the vocal. [AHD]

Duple – (1) Consisting of two; double. (2) Music Consisting of two or a multiple of two beats to the measure. [AHD]

dubplate or dub plate - An acetate one-off version of a vinyl record. The name comes from the Jamaican dancehall reggae scene in the early '70s where "dub" or instrumental versions of songs were produced so the vocalist could "toast" over the "riddims" in club settings.

ducker - A dynamic processor that lowers (or "ducks") the level of one audio signal based upon the level of a second audio signal. A typical application is paging: A ducker senses the presence of audio from a paging microphone and triggers a reduction in the output level of the main audio signal for the duration of the page signal. It restores the original level once the page message is over.

Dudley, Homer - Inventor of the vocoder. [Dudley, H. (1939) "The Vocoder," Bell Labs Record, 17, pp. 122-126]

duduk - An Armenian woodwind instrument.

dummy load - Any substitute device having impedance characteristics simulating those of the substituted device.

dundun - West African talking drum.

dununWest African bass drum not to be confused with the dundun.

duplex - Pertaining to a simultaneous two-way independent transmission in both directions. Often referred to as "full duplex" which is redundant.

DVD (Officially "DVD" does not stand for anything. It used to mean "digital versatile disc" -- and before that it meant "digital video disc" also once known as hdCD in Europe. See DVD Demystified for all the nitty-gritty.) A 12-centimeter (4.72") compact disc (same size as audio CDs and CD-ROMs) that holds 10 times the information. Capable of holding full-length movies and a video game based on the movie, or a movie and its soundtrack, or two versions of the same movie -- all in sophisticated discrete digital audio surround sound. The DVD standard specifies a laminated single-sided, single-layer disc holding 4.7 gigabytes, and 133 minutes of MPEG-2 compressed video and audio. It is backwards compatible, and expandable to two-layers holding 8.5 gigabytes. Ultimately two discs could be bounded together yielding two-sides, each with two-layers, for a total of 17 gigabytes. There are four main versions [Thank you Rane Corporation]:

DVD-Video - (movies) As outlined above.

DVD-Audio - (music-only) The standard is flexible, allowing for many possibilities, leaving the DVD-player to detect which system is used and adapt. Choices include 74 minutes for 2-chs at 24-bits, 192 kHz sampling, or 6-chs at 24-bits, 96 kHz, all utilizing lossless compression (type MLP for Meridian Lossless Packing). Quantization can be 16-, 20-, & 24-bits, with sampling frequencies of 44.1, 88.2, and 176.4 kHz, as well as 48, 96, and 192 kHz all supported. [See "DVD-Audio Specifications" by Norihiko Fuchigami, Toshio Kuroiwa, and Bike H. Suzuki, in the J. Audio Eng. Soc., Vol. 48, No. 12, December 2000, pp. 1228-1240 for complete details.]

DVD-ROM - (read-only, i.e., games and computer use)

DVD-RAM - (rewritable, i.e., recording systems). Matsushita (Panasonic brand) is currently the leader in density with 4.7 Gb and 9.4 Gb claimed for single-sided and double-sided discs respectively, compared with 2.6 Gb and 5.2 Gb offered by standard DVD-RAM technology. There are several competing formats:

DVD-R - (Hitachi, Pioneer & Matsushita) Primary 4.7 Gb application is peripheral drive for PCs, but is also of interest for video servers, video-disk cameras and other consumer applications.

DVD-RW - (Pioneer) Also 4.7 Gb aimed at VCR replacement.

DVD+RW or just RW (because it is not sanctioned by the DVD Forum) (Sony, Philips & Hewlett-Packard) Originally a 3-Gbyte system, positioned as a PC peripheral, but now expanded to a 4.7 Gbyte consumer version.

MMVF-DVD (NEC's 5.2 Gbyte Multimedia Video File Disk system) Now officially shifted from a laboratory project to a business project.

DVS (digital vinyl system or digital vinyl simulation) - Generic name for any of the vinyl emulation DJ systems ( Serato Scratch LIve, N.I. Traktor, etc.)

dynamics controllers (or dynamics processors) - A class of signal processing devices used to alter an audio signal based solely upon its frequency content and amplitude level, thus the term "dynamics" since the processing is completely program dependent. The two most common dynamics effects are compressors and expanders, with limiters, noise gates (or just "gates"), duckers and levelers being subsets of these. Another dynamics controller category includes exciters, or enhancers. And noise reduction units fall into a final dynamics processor category.

dynamic EQ - A technology that solves the problem of deteriorating sound quality as the playback volume is decreased. Dynamic EQ combines information from incoming source levels and actual output sound levels in the room or car to make moment-by-moment adjustments that compensate for the changes in human hearing at different listening levels. [Wikipedia]

dynamic microphone - A microphone design where a wire coil (the voice coil) is attached to a small diaphragm such that sound pressure causes the coil to move in a magnetic field, thus creating an electrical voltage proportional to the sound pressure.

dynamic range - The ratio of the loudest (undistorted) signal to that of the quietest (discernible) signal in a unit or system as expressed in decibels (dB). Dynamic range is another way of stating the maximum S/N ratio.

dynamo - A generator, especially one for producing direct current. [AHD]

dyne - A unit of force, equal to the force required to impart an acceleration of one centimeter per second per second to a mass of one gram. [AHD] Old units for sound pressure.





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HistoryOfRecording.com acknowledges the Elsevier, Inc. publication, Audio Engineering know it all, the University of Washington Press publication, The Audio Dictionary, second edition, the Howard W. Sames & Co., Inc. publication, Audio cyclopedia, the Cambridge University Press publication, The Art of Electronics, Rane Corporation (Dennis A. Bohn, CTO), Houghton Mifflin Company publication, The American Heritage Dictionary of the English Language, Fourth Edition, the IEEE publication, IEEE 100: The Authoritative Dictionary of IEEE Standards Terms, Seventh Edition and Wikipedia in the preparation of this Dictionary of Audio Terminology.

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