Файл: Sound Tech Terms Dictionary.pdf

D

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

delta modulation:  In the UK, often, and more properly called delta-sigma modulation.  A type

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

delta-sigma modulation:  See delta modulation.

delta time:  See SMF.

demodulator:  A device which recovers the audio signal from a modulated carrier waveform.
Also called a detector.  See amplitude modulation and frequency modulation.

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

depth perception:  See depth(1).

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

desk:  See mixer.

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

detune:  (1) (noun) A control that allows one oscillator to sound a slightly different pitch than

another.  (2) (verb) To slightly change the pitch of one oscillator relative to another, produc-
ing a fuller sound.

D

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

dialog normalization (DN):  There is a wide difference in the apparent loudness between

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

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

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

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

••••• •

••

T T S T T T S

•• •

•

•

T S T T S T T

••••• •

••

T S T T S T T

Diatonic Major Scale of C

Diatonic Minor Scale of A

Diatonic Minor Scale of C

Diatonic Major and Minor Scales

D

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

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

difference tone:  A tone produced by combining two tones which are not part of a harmonic

series, having a frequency difference of 20Hz or greater.  Any slower than 20Hz, and the dif-
ference of the two notes will be perceived as a pulse, called beating.  Also called a resultant
tone.  Also called a Tartini tone.

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

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

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

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

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

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

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

D

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

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

digital audio extraction:  See grabbing.

Digital Audio Mastering System:  See digital multitrack.

Digital Audio Recorder (DAR):  Any type of audio recording system which records upon a

digital medium, such as DAT or hard disk.  DAT or DCC recorders, digital dubbers, digital
multitracks, and hard-disk recording systems are all example of digital audio recorders.
These recorders are an alternative to analog recorders, such as traditional cassette or reel-to-
reel formats which do not convert the waveform to a digital representation prior to writing it
to the recording medium.

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

Digital Compact Cassette:  A type of recording format announced by Philips in 1990, de-
signed to compete with the R-DAT format.  The system allows for the recording and play-
back of analog cassettes as well as DCCs on the same machine.  Uses PASC (Precision
Adaptive Subband Coding), derived from the MPEG-1, Layer 1 data reduction system to
provide data compression (lossy) for the recording of digital audio on 

1

8

” wide magnetic

tape at 1

7

8

 ips.  This format has not been widely adopted.  Sometimes called DCAC for

Digital Audio Compact Cassette.  See also MiniDisc, DAT, and CD.

digital delay line (DDL):  See delay line.

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

digitally controlled amplifier:  See DCA.

digitally controlled oscillator:  See DCO.

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

D

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

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

digital time delay:  See delay.

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

Digital TeleVision (DTV):  See DTV.

digital watermark:  The solution for a piracy and duplication protection scheme developed

jointly by Sony and Philips which writes copyright data encrypted within the CD/DVD etc.
disc itself.  This scheme would, for example, encode discs with a country code so that these
discs would only play on players from the same country.  This is presumably better than
older forms of digital copy protection which tried various pilot tones or random number gen-
erators, failing ultimately because the results were either too audible or too easy to circum-
vent.  In a digital watermark, the copyright data are stored as a modulation of the width of
the injection-molded pits.  Duplicating the watermark would require the same equipment as
that which produced the disc stamper, the distribution of which is presumably tightly con-
trolled.  It is also possible to synchronize the modulation of the pit widths so that there is a
visible pattern formed on the disc pit substrate itself, making an “analog” watermark (with-
out the need for water, of course.)  In addition to the watermark and country codes, identifi-
ers for the mastering house and pressing plant, glass master number, ISRC catalog numbers,
etc. can be stored.

The digital watermarking technology has been called Pit Signal Processing (PSP) which
works by modulating the strength of the laser used to record the digital data onto the glass
master.  One by-product of the watermarking process is that the EFM used to encode audio
data onto the CD master allows the pits to vary in length between 3-11 units.  These slight
errors in length, or “jitter” result in slight timing errors which can cause a smearing of the ste-
reo image as well as an increase in HF noise.  The more rigid requirements of pit length
control in watermarking should result in a significant reduction of pressing-induced jitter,
just generally improving the CD production process.

diminuendo:  Synonym for decrescendo.

diminution:  (1) The reduction of a major or perfect interval  by one half-step to make a di-
minished interval.  (2) The appearance of a musical idea in note durations which are shorter
than those used for its first appearance.  The opposite of augmentation.  (3) A method orna-
mentation where notes of long duration are broken into a number of shorter notes, often at
different pitches, e.g., a trill.