DA-88 Tascam's model number for their digital multitrack recorder using Sony-developed "Hi8" 8mm videotape as the storage medium. Becoming a generic term describing this family of recorders. See DTRS.
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) Telephony. 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 new 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. The DAC is the last link in the digital chain of signal processing. See data converter bits.
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. Perhaps an example best illustrates this principle: let's say you have a speaker cabinet nominally rated at 8 ohms, and you are driving it with a Rane MA 6S power amp through 50 feet of 12 gauge cable. Checking the MA 6S data sheet (obtained off this website, of course), you don't find its output impedance, but you do find that its damping factor is 300. What this means is that the ratio of a nominal 8 ohm loudspeaker to the MA 6S's output impedance is 300. Doing the math [8 divided by 300] comes up with an amazing .027 ohms. Pretty low. Looking up 12 gauge wire in your handy Belden Cable Catalog (... then get one.) tells you it has .001588 ohms per foot, which sure ain't much, but then again you've got 100 feet of it (that's right: 50 feet out and 50 feet back -- don't be tricked), so that's 0.159 ohms, which is six times as much impedance as your amplifier. (Now there's a lesson in itself -- use big cable.) Adding these together gives a total driving impedance of 0.186 ohms -- still pretty low -- yielding a very good damping factor of 43 (anything over 10 is enough, so you don't have to get extreme about wire size). [Note that the word is damp-ing, not damp-ning as is so often heard -- correct your friends; make enemies.]
Daniels, Drew (1947-2010) American "pro audio icon." [MIX magazine.]
Daniels, Yvonne See: disc jockey.
Dansette Phonograph. World's first portable record player brought out in 1952 by the British company, Margolin.
dan tranh Musical Instrument. A Vietnamese plucked string instrument.
DAR (digital audio radio) EIA term for the next generation of digital radio broadcasting standards.
Darbuka See: goblet drum.
DAS (distributed acoustic sensing) A system that uses fibre-optic cables for distributed strain sensing that is then measured using optoelectronics devices. Hit the link for details.
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) 1. A digital audio recorder utilizing a magnetic tape cassette system with rotary heads similar to that of a video recorder. 2. A little bit of something as in dis & dat.
data cables Analog audio signals require a relatively small bandwidth and are interconnected using standard cables. In contrast to analog audio, digital audio and digital control signals require a very large bandwidth and must be interconnected with specially designed data cables. See Category cables.
data compression See: digital audio data compression
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. When an analog signal is sampled (at the sampling frequency), it is being sliced up into vertical pieces. Each vertical piece is then estimated as to its amplitude (How large is the audio signal at this instant?). This estimation process is the data converters job. It compares the original signal against its best estimate and chooses the closest answer. The more bits, the more choices the data converter has to choose from. The number of choices is the number "2" raised to the number of bits (this explanation is simplified for clarity). For example, 16-bits creates 2 to the 16th power of choices, or 65,536 possible answers for the converter to choose from. And the higher the sampling rate, the more slices for any given time period. Again, the more slices, the more accurate will be the data conversion. All of which, ultimately determines how well the reproduced signal sounds compared to the original. For example, if a signal is recorded using "16-bits at 48 kHz", then for every one second of the audio signal, it is sliced up into 48,000 pieces. Then each piece is compared against a ruler with 2 to the 16th graduations, or 65,536 voltage levels. Each sample instant is compared against this ruler and one value is assigned to represent its amplitude. For each second, 48,000 samples are given specific values to represent the original signal. If the same signal is recorded using "24-bits at 96 kHz" then for the same one second period, there will be 96,000 slices, or samples, and each one will be compared against a voltage ruler now divided into 2 to the 24th divisions, or 16,777,216 choices. Obviously this converter can choice an answer that is far closer to the original than before, and it gets to do this for twice as many samples. All of which, in the end, means this converter recorded samples that more closely approximated the original audio signal. [Where it gets interesting is in trying to answer the question of what is enough? Sure, more bits are more accurate, but can the human ear tell the difference. In most cases, once you go beyond true 16-bits, the answer is no. All benefits above 16-bits/48 kHz are very small refinements, not monumental improvements. What really is going on, is that the advertised "16-bit/48 kHz" recordings of yesterday weren't. They used 16-bit converters but their accuracy was not 16-bits, it was more like 14-bits. Similarly today, the advertised "24-bit" converters are not 24-bit accurate, but they are certainly at least 18-bit accurate, and that makes an audible difference. So, if you can find a true 16-bit system and compare it with a typical 24-bit system of today, they will sound very nearly identical. And the sampling rate getting faster makes even less of an audible difference. For example if you compare a typical 16-bit/96 kHz system against a 24-bit/48 kHz, you will pick the 24-bit system every time. If you have a choice, always choose more bits, over a higher sampling rate.] See the RaneNote Digital Dharma of Audio A/D Converters.
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.
Day, Doris Stage name of Doris Kappelhoff.
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. First made popular by IBM in their AT personal computer in the mid-80s. (The "D" originally described the shape of the housing. The second letter: A, B, C D or E originally specified the size of the housing somewhat like drawing sizes. [Newton])
DB-25 connector A 25-pin D-shell connector originally standardized for RS-232 serial communications.
dB (decibel) See decibel.
dBA See decibel.
dBC See decibel.
dB calculator Handy online calculator
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 (yes, 177 dB-SPL!).
DC See: direct current.
DC-300 Power amplifiers. 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. And at that time the DC-3 was a popular aircraft so it all fit together nicely.
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. (Now discontinued.)
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 -- e.g., a modem or printer. See: DTE. The main difference between DCE and DTE is the wiring of pins 2 and 3, thus the need for a null modem cable when tying two computers together.
DC offset Electronics. The amount of extra input voltage required to produce exactly zero output voltage with no applied signal. [In a perfect device if there is no input signal then there would be no output signal, but, alas, 'tis not the case -- ever. There is always some small output voltage present even with no input signal unless the offset voltage has been corrected.
DE-9 connector See DB-9 connector.
deadly nevergreen An English word no longer in print (except here) meaning the gallows (late 18th, early 19th centuries).
Dead Musician Directory "A site about dead musicians ... and how they got that way" Hey! Don't laugh, these guys are dead serious. Dead Rockers, jazz, reggae, bluegrass, etc.
Dead Recording Media (This was the original name, now renamed The History of Sound Recording Technology. I guess someone complained.) A great chronicle of obsolete devices compiled by David L. Morton: "... site devoted to the dead, dying, or very ill technologies of sound recording."
decade A tenfold increase or decrease in any quantity.
decay Electronics. A gradual magnitude decrease of signal level, occurring immediately after a signal reaches its peak. Contrast with attack.
Decca tree Microphones. 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"; however this never caught on, probably for brevity reasons if no other.] Hit this link for an online dB calculator. Good tutorials with charts: "Can You Tell The Decibel?" by Hugh Covill [Tip: click on the chart to make it bigger], and "Quick dB Reference Chart" by Pat Brown.
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).]
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. [According to standards people, there's supposed to be a space between "dB" and "FS" -- yeah, right, like that's gonna happen.]
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 -- an unbelievably small value.
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. [Thanks to Bob Pease for pointing out these enlightening facts.] And higher positive pressures are called shock waves, not sound. [Thanks to "Someone" for this distinction.] [Thanks also to Chuck McGregor for the clarifying language.]
dBPa Preferred informal abbreviation of the official dB (Pa); a reference point equal to 1 Pascal.
decibel calculator Handy online calculator
decimal digit Everyday normal, base-10 numbers.
deck Music. Popular DJ jargon for turntables and sometimes CD players.
decoupling capacitor See: bypass capacitor.
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 See pre-emphasis.
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. See the RaneNote, "Dynamics Processors: Technology & Applications."
De Forest, Lee (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]
degauss 1. To neutralize the magnetic field of (a ship, for example). 2. To erase information from (a magnetic disk or other storage device). [AHD]
degree 1. Physics. A unit division of a temperature scale. 2. Mathematics. A planar unit of angular measure equal in magnitude to 1/360 of a complete revolution. 3. Cartography. A unit of latitude or longitude, equal to 1/360 of a great circle. [AHD] See: 360 to find out why "360" and not some other number.
deja-booboo "The inexorable feeling that you've made this mistake before." -- [Pseudodictionary.com]
déjà vu Psychology. The illusion of having already experienced something actually being experienced for the first time. [AHD] [Note that this is the original meaning, which is to think you have experienced something that in fact you have not. It does NOT mean to repeat something that you know you have done before, even though that is the most found usage. As maybe you can tell, misuse of this term is one of my pet peeves.]
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. 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. 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.
Dell, Jr., Edward T. (1923-2013) Legendary audio guru founder and publisher of Audio Amateur magazine.
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 See delta-sigma modulation
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 (see: Sampling (Nyquist) Theorem). 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. See the RaneNote Digital Dharma of Audio A/D Converters.
Deramic Sound System A registered trademark (now expired) of the Deram Records division of Decca records.
dereverberation Acoustics. Reverberation reduction; alternative term for room correction (or compensation or equalization -- exchangeable terms). All use advanced DSP methods to improve room acoustics.
Descartes, René (1596-1650) French mathematician and philosopher. Considered the father of analytic geometry, he formulated the Cartesian system of coordinates. [Then there's the story about how Descartes met his ultimate demise: It seems he was in a bar in Paris sipping a glass of Kir when the bartender asked if he would like another. M. Descartes responded "I think not," whereupon he disappeared without a trace.] (Thanks to Glenn D. White for this.)
deserializer A serial-to-parallel data converter; used in buses and networks.
destructive solo See: solo.
Detroit Jit Dance. A '70s street dance featuring very fast foot movements, danced to non-vocal techno-rock..
device driver See: driver.
DFD (difference frequency distortion) See IM.
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 See direct box.
Diagram Prize The name of the award given by The Bookseller, a British magazine, for the oddest book title of the year. A couple of pro audio reference books come to mind as possible entries: Bebop to the Boolean Boogie and Spaces Speak, Are You Listening?.
diapason 1. A full, rich outpouring of harmonious sound. 2. The entire range of an instrument or voice. 3. Either of the two principal stops on a pipe organ that form the tonal basis for the entire scale of the instrument. 4. The interval and the consonance of an octave. 5. A standard indication of pitch. 6. A tuning fork. [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 Hearing. Pertaining to different sounds present at both ears. Contrast with diotoc.
dichotic listening Hearing. Listening to a different message in each ear at the same time.
Dickinson, Jim (1941-2009) American musician/producer who became a great cult hero to many musicians including Bob Dylan.
dictionary "A malevolent literary device for cramping the growth of a language and making it hard and inelastic. This dictionary, however, is a most useful work." -- Ambrose Bierce.
Diddley, Bo See Bo Diddley.
Diddley Bow (also seen as Diddlie Bow) Musical Instrument. A one-string guitar made by stretching a string between two nails in a door. Native to the Mississippi Delta region. [Thanks PT!]
dielectric constant See permittivity.
difference frequency distortion (DFD) See IM.
difference-tone IMD See IM.
differential amplifier Electronics. 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. Invented by Otto Herbert Schmitt in 1934 while still a graduate student. [Otto H. Schmitt, "A Simple Differential Amplifier," Review of Scientific Instruments8 (April 1937): 126-127.] Although Schmitt arrived at his version of the differential amplifier independently, L. A. Geddes has recently pointed out that a few others developed a similar device at around the same time. [L.A. Geddes, "Who Invented the Differential Amplifier?" IEEE Engineering in Medicine and Biology Magazine 15 (May/June 1996): 116-117.]
differential crosstalk 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. A nice visualization diagram is presented by Howard Johnson in his EDN article Visualizing differential crosstalk
differential Manchester encoding A signaling method used to encode clock and data bit information into bit symbols. Each bit symbol is split into two halves, or signal elements, where the second half is the inverse of the first half. A 0 bit is represented by a polarity change at the start of the bit time. A 1 bit is represented by no polarity change at the start of the bit time. Differential Manchester encoding is polarity-independent. [IEEE] Used in AES3
diffraction Acoustics. 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. First invented by Manfred R. Schroeder ["Diffuse Sound Reflection by Maximum-Length Sequences," J. Acoust. Soc. Am., Vol. 57, No. 1, pp 149-150, Jan 1975], and made commercially successful by Dr. Peter D'Antonio and his company RPG Diffusor Systems. See D'Antonio's book, Acoustic Absorbers and Diffusers: Theory, Design, and Application for more info. Diffusors are the acoustical analog of diffraction grating -- see above.
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. Well-designed algorithms ensure "lost" information is inaudible -- that's how you win the game.
digital audio watermarking See watermarking.
digital clipping See 0 dBFS.
digital device An unintentional radiator (device or system) that uses digital techniques and generates and uses timing signals or pulses at a rate in excess of 9000 pulses (cycles) per second; inclusive of telephone equipment that uses digital techniques or any device or system that generates and uses RF energy for the purpose of performing data processing functions, such as electronic computations, operations, transformations, recording, filing, sorting, storage, retrieval, or transfer. [FCC 47CFR Part 15]
digital hybrid See hybrid.
digital overs See overs.
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.
digital techniques Defined by Kevin Frank, Dir. R&D, Rane Corporation, as the utilization of boolean logic at TTL, CMOS or equivalent logic levels.
digitization Any conversion of analog information into a digital form.
dimdi Musical Instrument. Native to India, a hand drum with one skinhead.
diminished fifth 1. 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. 2. What's left after you've had a few shots. [Thanks GD]
din A jumble of loud, usually discordant sounds. [AHD]
DIN Acronym for Deutsche Industrie Norm (Deutsches Institut fuer Normung), the German standardization body.
diotic Hearing. 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 Loudspeakers. 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] In dipole woofer designs the rear wave is left untreated, and the overall system response is tuned by varying the baffle size and the system "Q." It acts like a figure-of-eight source and thus excites room modes less than monopole woofer systems. For detailed theory and DIY examples buy the Linkwitz Labs Archive CD-ROM, the best source available.
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 (See usage note) An electric current that flows in one direction. Contrast: alternating current. [IEEE] [Usage Note: Officially the IEEE dictionary is very clear that the abbreviation for direct current is "dc" not "DC." However most everyone agrees (mags, technical journalists, me, etc.) that when abbreviating direct current in a standalone sense, that it looks better and reads clearer if you use uppercase, e.g., "The device runs off DC voltage," instead of "The device runs off dc voltage," particularly if the abbreviation begins or ends a sentence. Imagine a sentence like this: "Dc is a type of generator voltage." Or, "Do you want ac or dc?" Both work better with uppercase. As for Vdc vs. VDC, both are seen and accepted even though Vdc is the IEEE standard.]
directional microphone One whose response is more sensitive to sound arriving from one direction than another. See unidirectional microphone.
directivity Loudspeakers. The ratio, expressed in dB, of the on-axis sound power to the overall power output of the loudspeaker at a particular frequency. Microphones. See: microphone polar response.
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. See also early reflections.
disambiguate To establish a single grammatical or semantic interpretation for. [AHD
disc The term used for any optical storage media. Originally popularized to refer to phonograph records. From Latin discus, the term refers primarily to audio and video storage systems, such as compact discs, laserdiscs, etc., but the advent of CD-ROMs and computer optical storage units blurs this distinction. Compare with disk.
disc jockey Abbr. DJ From Wikipedia: "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.
disc lathe See: stereo disc lathe.
disco ball or mirror ball A round ball covered with small mirror pieces that reflect light as it turns producing a dazzling display throughout the dance floor. [Been around since 1897 as amazing as that seems.]
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 Music. Disagreeable in sound; harsh or dissonant. [AHD]
discrete Constituting a separate thing; distinct, or a set of distinct things. [AHD]
discrete component An electrical element that is mounted on a printed circuit board or other substrate and connected to the interconnect wiring system, but is not integrated to any significant extent with other elements and does not contain boundary module test circuitry adjacent to its pins. [IEEE]
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 paced. See Fourier theorem.
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. Compare with disc.
Disklavier Musical Instruments. Yamaha's family of reproducing ("player") pianos.
dissonance A harsh, disagreeable combination of sounds; discord. Music. A combination of tones contextually considered to suggest unrelieved tension and require resolution. [AHD] Psychoacoustics. The sense of roughness or lack of blending that is heard when certain combinations of musical tones are played together outside a musical context. [Bregman]
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 Audio 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. If a piece of gear is perfect, it does not add distortion of any sort. The spectrum of the output shows only the original signal -- nothing else -- no added components, no added noise -- nothing but the original signal. See the RaneNote Audio Specifications.
distortion box See: effects boxes.
distributed acoustic sensing See: DAS.
distributed mode loudspeakers (DML) See bending wave.
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. See the RaneNote Digital Dharma of Audio A/D Converters. For the theory behind dither see stochastic resonance.
diversity antenna Radio Broadcast. 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.
djembes (pronounced "jem-bay") Musical Instruments. A goblet shaped hand drum that is the most popular African drum.
DJ mixer For a history of, see David Cross's master thesis: The History of the DJ Mixer.
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. See TI's DLP website.
DMD (digital micromirror device) See DLP above.
DML (Distributed Mode Loudspeakers) See bending wave.
DMM (digital multimeter) See VTVM.
DMX (Digital Music Exchange) A licensing music service provider.
DMX512-A (Digital Multiplex with 512 pieces of information channels) The standard is "Entertainment Technology—USITT DMX512-A—Asynchronous Serial Digital Data Transmission Standard for Controlling Lighting Equipment and Accessories", was approved by the American National Standards Institute (ANSI) in November 2004. This is a daisy-chain network standard originally designed for lighting control but is now expanded into many other network-able accessory items.
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 Atmos® See: Atmos®
Dolby Digital® Dolby's name for its format for the digital soundtrack system for motion picture playback. Utilizes their AC-3 system of digital compression. The signal is optically printed between the sprocket holes. Now being introduced to home theater on laserdisc and DVD. Dolby Digital may use any number of primary audio delivery and reproduction channels, from 1 to 5, and may include a separate bass-only effects channel. The designation "5.1" describes the complete channel format. Surround decoder systems with Dolby Digital automatically contain Dolby Pro Logic processing to ensure full compatibility with the many existing program soundtracks made with Dolby Surround encoding. No abbreviations are to be used.
Dolby, Ray (1933-2013) American engineer, inventor, sound pioneer and founder of Dolby Labs. Dolby first major success was developing a noise reduction circuit that gave a 10 dB improvement in the signal-to-noise ratio for cassette players. He parlayed that 10 dB improvement into a billion dollar enterprise.
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.
doo wop Music. A vocal harmony genre of music begun in the 1940s.
Doppler effect [After Christian Johann Doppler, 1803-1853, Austrian physicist and mathematician who first enunciated this principle in 1842.] 1. 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. 2. Gave rise to the variation known as the dope-ler effect, defined as the phenomenon of stupid ideas that seem smarter when they come at you in rapid succession. [Thanks JF.]
DOS (pronounced "doss") (disk operating system) A software program controlling data in memory, disk storage, running programs and I/O management.
double 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). See: double bass below.
double balanced See cables.
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. Also referred to as a baroque doghouse for its deep tones. See Slatford for historical details.
double-blind comparator See ABX testing.
Double MS See MSM.
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 See birefringence.
doubling Recording. 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. The most famous use of doubling is that done by Roger Nichols on Donald Fagen's vocals and Walter Becker's instruments in all Steely Dan recordings.
Doumbek See: goblet drum.
downstage Theater. The front of the stage closest to the audience, as opposed to upstage.
downward expander See expander.
Drag and Drop 1. 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] For an example, see the Drag Net GUI. 2. Not to be confused with dragon drop -- a mess created by a fire-breathing creature. (Thanks CD.)
DRACULA (Dynamic Range Audio Controller with Unobtrusive Level Adjustment) Acoustics. BBC System for reducing the dynamic range of musical sources for AM and FM broadcasts.
drain Semiconductors. A device electrode whose current flow is controlled by the conductivity of the semiconducting channel. Typically, the drain electrode is identical physically to the source electrode. The sign of the voltage at which the drain electrode is biased relative to the source electrode depends on the nature of the majority carriers: The bias is more positive for electrons and more negative for holes. [IEEE]
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.
drawing symbols See: architectural drawing symbols
dreamt The only English word ending in the letters "mt."
driver 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.
dropout voltage (or current) The voltage (or current) at which a magnetically operated device will release to its de-energized position. It is a level of voltage (or current) that is insufficient to maintain the device in an energized state. [IEEE]
dry circuit See below.
dry transformer Telephony. 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. Contrast with wet transformer.
DSD® (Direct Stream Digital®) See SACD.
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.
DSS See: Deramic Sound System Debuting September 7-8, 1967 at the British Decca Records sales conference, it was tagged as "The Sound of the 70s." Claimed was a "new fore and aft dimension, a near and far perspective as well as the usual sideways spread of stereo" as well as being referred to as "sound in the round." "The technical data behind the system was not revealed at the conference beyond attribution it to a couple of unrelated electronic breakthroughs." [Quotes from Billboard magazine, September 23, 1967, page 64, International News Reports.]
DSX (dynamic surround expansion) Surround sound. 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) Loudspeakers. A type of direct digital loudspeaker. Compare: MVCDL.
D-taper See potentiometer.
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. See: DCE. The main difference between DTE and DCE is the wiring of pins 2 and 3, thus the need for a null modem cable when tying two computers together. 2. CobraNet refers to DTEs as the source and sink devices on the network, i.e., they source and sink audio. Rane's NM 48 & NM 84 Network Mic/Line Preamps are DTE devices.
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. [See Usage Note under AES3 for transmission gotcha caveats.]
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.
duality 1. The quality or character of being twofold; dichotomy. [AHD] 2. Physics. The wave-particle theory of light is a duality. 2. 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. Here are some important electronic-pairs:
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]
duda Musical Instrument. Hungarian bagpipe constructed from goat skin.
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 DJ. 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.
dubstep An electronic dance music genre.
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. Another use is for talkover.
duduk Musical Instrument. An Armenian woodwind instrument.
duplex Pertaining to a simultaneous two-way independent transmission in both directions. Often referred to as "full duplex" which is redundant. See also half-duplex.
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:
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.
dwell time The duration, starting at the point in time when the measurement voltage is applied to the time when the measurement is recorded. It is used to minimize measurement errors due to transient noise. Alternatively, the sweep speed can be adjusted.
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. See the RaneNote"Dynamics Processors: Technology & Applications."
dynamic EQ See the RaneNote, "Dynamics Processors: Technology & Applications, Chapter 4."
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. Works in almost the exact opposite of a dynamic loudspeaker where an electrical voltage is applied to the voice coil attached to a large cone (diaphragm) causing it to move in a magnetic field, thus creating a change in the immediate sound pressure. In fact, under the right circumstances, both elements will operate as the other, i.e., a dynamic loudspeaker will act as a microphone and a dynamic microphone will act as a loudspeaker -- although not too loud. See electromagnetic induction.
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. With reference to signal processing equipment, the maximum output signal is restricted by the size of the power supplies, i.e., it cannot swing more voltage than is available. While the noise floor of the unit determines the minimum output signal, i.e., it cannot put out a discernible signal smaller than the noise. Professional-grade analog signal processing equipment can output maximum levels of +26 dBu, with the best noise floors being down around -94 dBu. This gives a maximum dynamic range of 120 dB -- pretty impressive numbers, which coincide nicely with the 120 dB dynamic range of normal human hearing (from just audible to uncomfortably loud). See the RaneNote Audio Specifications.
dynamo A generator, especially one for producing direct current. [AHD]