Audio Terminology And Definitions Dictionary
digital-to-analog converter is an electrical circuit that converts a binary
coded word (a "sentence" of 0s and 1s) into an equivalent analog voltage
In an acoustical sense, we describe a room that doesn't reflect sound very
well as one that's heavily "damped." These rooms usually have curtained
walls, sound-absorbent ceilings, carpeted floors, lots of overstuffed furniture,
or some combination of these "damping" elements. People also provide
damping; an empty theater is more reflective than one that contains a large
audience. Speakers may be damped internally with foam, fiberglass, wool, or
other absorbent materials.
Damping Factor A measure of the control an amplifier exerts over a loudspeaker drive unit. Damping factor is a measure of amplifier output impedance relative to
Named after its designer, Joseph D'Appolito, this is a way of restricting a
loudspeaker's dispersion and limiting the area into which it radiates sound.
Speakers using the D'Appolito configuration place a tweeter between two
midrange drivers. The size of the drivers and their spacing is critical. When
properly executed, a D'Appolito configuration results in comparatively little
radiation above and below the center axis of the speaker, thus minimizing floor
and ceiling reflections.
DAT Digital Audio Tape. This format introduced in the late Eighties makes use of a rotating drum containing
a helical scan head similar to the sort used in video cassette recorders. Unfortunately disagreement between the recording and hi-fi industries led to a refusal by the major record companies to produce pre-recorded DATs or to sanction the release of a non-copyright protected digital tape recorder hardware. By the time a copyright protection system had been agreed,
DAT was dead on its feet as a mainstream consumer format.
Data Reduction Also
called "data compression." Any technique that reduces the amount of digital
data required to represent a given amount of information. Data reduction enables
large amounts of information to be easily and efficiently stored and
transmitted. For example, a technology that reduces data by 75 percent (4:1
compression) can store a 16-bit digital word in just four bits. Data reduction
technologies used for digital audio must have very carefully designed parameters
so as to have a minimal effect on the accuracy of the reproduced sound. (See
DC Abbreviation for direct current
DCC Digital Compact Cassette is Philips' backwards compatible digital cassette format. In addition to
playing and recording Digital Compact Cassettes, DCC recorders also play standard analogue cassettes. Hence the term backwards compatible. DCC tapes work to 16-bit 44.1kHz sampling. It also features Philips' PASC data reduction system. PASC selectively discards signals thought to be below the threshold of audibility. Soft signals audible in isolation may be masked by louder signals.
In such circumstances PASC eliminates the masked signals.
Decibel (or dB) The
dB is the most common—and most commonly misunderstood—measurement in audio.
It doesn't measure anything per se,
but rather it measures, on a logarithmic scale, the ratio between two values,
whether they be voltage, current, or, most commonly, sound pressure levels
(abbreviated dB SPL). An SPL that is 10dB louder than another is considered
twice as loud.
so-called "single-bit" digital signal format where each sample is described
in relative terms only. In other words, a sample in a delta-sigma data stream
can be only stronger or weaker than the preceding (or following) sample
.Delta-sigma signals are inherently less data-intensive than their PCM
equivalents. However, they can't be mathematically manipulated as easily,
which makes them somewhat more difficult to process. (Sometimes called sigma-delta.)
The surface of a driver, which pushes against the air to generate sound waves.
Examples include a cone or dome (dynamic speaker) or a membrane (planar
Dielectric The non conducting space/insulation between two conductors in a cable.
Digital A sampled analogue waveform encoded in the form of on/off pulses. The frequency with which the
analog waveform is sampled is its sampling frequency which, in the case of Compact Disc, is set at 44.1kHz (44,100 samples per second). The accuracy of sampling is determined by the word length of each sample. For Compact Disc it is 16-bit. Modern professional digital recorders are capable of almost
32-bit resolution at 384 kHz (as of June 2013).
Digital Coaxial Output An
electrical output connection for a raw digital data stream that uses a single
cable with RCA connectors at each end. (See also: digital
Digital Filter Any
filter used in the digital domain. CD players use oversampling to raise unwanted
frequencies away from the audio range. Digital filtering does not produce the
phase distortion common to analog filtering.
Digital Optical Output
An optical output connection for the digital
data stream. The most common connector today is TOSLink, although the older
AT&T "glass" connector is still preferred by some. (See also: digital coaxial output.)
Digital TV An
FCC-approved television transmission system wherein the video and audio portions
are transmitted digitally and not as analog data. With digital television, the
signal is basically "on" or "off." In other words, the
intent of DTV technology is that the viewer sees either a good image or nothing
at all. There is no gradual signal loss as distance from the transmitter
increases. DTV broadcasts can be standard definition, intermediate definition,
or high definition. Thus, all HDTV broadcasts are considered DTV, but not
all DTV is HDTV.
Diode The thermionic diode invented in 1904, marks the start of the electronics era. It is the first device for
controlling the flow of current in relation to applied voltage, and comprises two electrodes, the heated cathode (electron source) and anode (electron receptor).
loudspeaker that radiates equal amounts of energy in two opposite directions
with opposite polarity. The compressions and rarefactions that constitute sound
waves move outward from each side of the enclosure in inverse symmetry (i.e.,
while one side of the enclosure produces a positive pulse, the opposite side
produces a negative pulse). (See also: bipolar.)
Direct Circuit Paths To
employ remote switching wherever possible. In this fashion, we bring the switch
to the circuit, rather than lengthening the signal path. Contact points are also
kept to a minimum. This helps prevent radio frequency pickup and achieve a lower
subjective noise floor.
Direct Current Current that does not have a positive or negative value. Usually referred to as
Directionality The tendency in some loudspeakers to beam sound like a laser rather than radiate it equally in
all directions. Horn, ribbon and electrostatic speakers tend to be more directional at high frequencies than well designed dome moving coil tweeters, a factor that in extreme situations can impose restrictions on
listening and speaker position.
Direct Radiator A
loudspeaker that radiates its energy in one primary direction. Also called
a monopole speaker.
The characteristic angle over which a speaker projects sound. Dispersion is
usually measured by attenuation in dB as a measurement microphone is moved from
in front of the speaker to off to the side of the speaker. It is usually
expressed in dB and degrees relative to the speaker's on-axis response. For
example, a typical speaker might have a frequency response that is down 3dB at
5000 Hertz 60 degrees off-axis relative to its on-axis response. Because of the
laws of physics and acoustics, speakers tend to have narrowing dispersion with
unintended or accidental alteration of an original signal. Distortion can take
many forms, the most common being harmonic
and intermodulation distortion.
Our aural perceptual system tolerates relatively high distortion if the
distortion is mathematically related to the original signal, but our ears are
intolerant of random distortions that are unrelated to the original signal.
Dither A low level random noise added to a digital signal to mask highly audible forms of digital distortion.
Another video compression format, DivX is used primarily for sending video files
over the Internet, DivX is based on MPEG4. It produces very small files by
compressing a great deal of video content while maintaining reasonably good
image quality. Note:
This is the second time the name DivX has been used. The first
so-named system was an attempt to market time-sensitive DVDs that would be
unplayable after a set period of time.
An acronym for Digital Light Processing, a display technology developed by Texas
Instruments. DLP uses a chip called a DMD, or Digital Micromirror Device. Today,
DLP displays are used primarily for video projectors.
DMM Direct Metal Mastering. An LP disc mastering process in which silvering and electroplating stages
Dolby Digital Also
known as AC-3, this is Dolby's original technology that utilizes digital
processing to deliver 5.1 discrete channels of audio. In its full
implementation, Dolby Digital uses five "full-bandwidth" channels (left,
right, center, left surround, and right surround) as well as a bass-only
low-frequency effects channel for information below 100 Hz. This bass-only
channel is the ".1" of the full 5.1 array because it covers approximately
one-tenth of the frequency range of a full-bandwidth channel.
Dolby Digital EX
Based on Dolby Digital, the "EX" extension adds a sixth full-range channel,
with its speaker located directly behind the listener/viewer.
Dolby Digital +
Dolby Digital Plus, or Enhanced AC-3 (E-AC-3), is a surround sound audio codec
designed for evolving applications such as streaming media, computer audio,
mobile phones, and other internet-based uses. It supports up to eight channels
Dolby HX Pro A form of signal processing during recording which prevents self biasing of the signal. HX Pro
thus protects loss of high frequency signals through unwanted compression, a useful feature in cassette
Dolby Noise Reduction
Any of a number of double-ended (record
encode/playback decode) systems designed to reduce the noise inherent in analog
tape recording and mixing. The first example, Dolby A, was designed for
professional applications. Dolby B was specifically developed as a consumer
format. Dolby C and S formats, both consumer technologies, expand Dolby B's
capabilities. Dolby SR is an advanced professional technology.
A significant step in the transition from
stereo to multi-channel sound, this matrix (non-discrete) audio delivery system
provides a center channel and enhanced separation, thanks to special "steering" circuitry, for more accurate spatial presentations.
Dolby ProLogic II
A surround sound decoding technology that was developed jointly by Jim Fosgate
and Dolby Labs. Dolby ProLogic II can create a "simulated" 5.1 channel
surround environment from any two-channel source (such as stereo CDs) as well as
from a four-channel Dolby Surround signal. It is not a discrete format, but
it makes effective use of matrixing to deliver an adequate 5.1 representation of
a stereo film or music soundtrack. (Also called PL II.)
Dolby ProLogic IIx
This adds two rear channels to Dolby Pro Logic II's 5.1 channels, thus making it
a 7.1 channel surround decoding system. (Also called PL IIx.)
Dolby ProLogic IIz
An enhancement to earlier ProLogic approaches, Pro Logic IIz offers the option
of adding two front height speakers positioned directly above the main left and
right speakers. This adds a vertical component to the surround sound field.
(Also called PL IIz.)
Dolby 70mm Six-Track A
commercial film sound process that records six individual soundtrack channels
(left, center, right, left surround, right surround, subwoofer) on magnetic
stripes that have been "painted" onto the 70mm film print. The soundtracks
are then read by magnetic tape heads on the projector and reproduced in the
theater. Dolby 70mm Six-Track is a discrete analog format using no matrix
encoding or decoding. Films made with it can be shown only in specially equipped
theaters. Although it offers improved audio performance compared to Dolby
Stereo, it is rarely used today because of the expense involved in making
Dolby Stereo Now
largely replaced by Dolby Digital, Dolby Stereo is an analog delivery system
that allows four individual soundtrack channels (left, center, right, surround)
to be recorded onto a 35mm film print using only two optical soundtracks. The
four tracks are then recovered when the film is projected. Dolby Stereo uses an
analog active matrix encode/decode process and either Dolby A or Dolby SR noise
reduction to achieve high-fidelity surround sound in motion picture theaters.
Dolby Stereo Digital
Also called Dolby SR-D or simply Dolby Digital,
this is the commercial iteration that allows six individual soundtrack channels
(left, center, right, left surround, right surround, and LFE or subwoofer) to be
optically printed onto a 35mm film and reproduced in commercial movie theaters.
The information is digitally encoded and printed on the film strip in the area
between the sprocket holes on the left-hand side of the film. The data is read
optically when a film is projected, and is then decoded and reproduced in the
Dolby Surround Can be used to refer to either:
1.) Dolby Stereo soundtracks that have been transferred to
home video formats (e.g., broadcast, VHS tape, laserdisc). With the exception of
Dolby A or Dolby SR noise reduction, a Dolby Surround consumer soundtrack is
identical to the Dolby Stereo theatrical soundtrack, with the four original
tracks remaining encoded onto two stereo tracks. This enables software with
Dolby Surround–encoded soundtracks to be played back on home video systems
that have mono, stereo, Dolby Surround, or Dolby ProLogic capability. Obviously,
this process is not currently promoted, as Dolby Digital has largely taken its
2.) Name given to the passive decoding technology used in
early consumer products that can extract only three (LRS) channels of a Dolby
Surround soundtrack's four channels of information. Largely replaced in
consumer equipment by Dolby Pro Logic decoding, which was, in turn, replaced by
PL II, PL IIx, and, most recently, PL IIz.
Dolby Surround Digital
Can refer to: 1.) Dolby Stereo Digital
soundtracks that have been transferred to home video formats. The soundtrack is
identical to the Dolby Stereo Digital theatrical soundtrack, with the six
original tracks encoded onto a digital track on the software.
2.) The digital decoding technology that can extract all six
channels of a Dolby Surround Digital soundtrack from a laserdisc or
satellite/cable transmission and reproduce them in home video applications.
Dolby TrueHD A
digitally based surround sound format. It supports up to eight channels and is
bit-for-bit identical to a studio master recording. It is one of the several
audio formats used by Blu-ray discs.
In a loudspeaker, any element (dynamic woofers and tweeters, electrostatic
panels, ribbons, etc.) that moves in direct response to a signal from an
amplifier.( See also: midrange driver,
tweeter, and woofer.)
that allows for hardware to communicate with another hardware devices.
(Direct Stream Digital) A single-bit digital data structure used for
high-density recording and SA-CD discs. DSD signals are composed of a very
high-speed series of individual bits that define amplitude differences
rather than absolute values.
abbreviation for Digital Theater Systems, DTS refers to a number of surround
sound formats that promise enhanced sound quality. The basic technology is known
simply as DTS and is a 5.1-channel encoding and decoding system similar to Dolby
Digital 5.1. DTS, however, uses less compression in the encoding process. As a
result, some feel that DTS provides a better listening experience.
DTS 96/24 While
not truly a separate surround sound format, 96/24 is an "upscaled"
version of DTS 5.1. Instead of using the standard DTS 48 kHz sampling rate,
96/24 employs a higher 96 kHz sampling rate. Also, 96/24 extends DTS 5.1's
16-bit depth to 24 bits.
A matrix technology, DTS Neo:6 is a surround
sound format that mimics Dolby Pro Logic II and IIx. It can extract a
6.1-channel surround field from existing analog two-channel material, such as a
stereo CD, movie soundtrack, TV broadcast, etc.
Introduced in 2011, this is an 11.1-channel surround sound format. DTS Neo:X
takes cues already present in either 5.1 or 7.1 channel soundtracks and creates
height and width channels that route to additional height and width speakers for
(Matrix and Discrete) DTS-ES actually refers to two 6.1-channel
surround encoding/decoding systems: DTS-ES Matrix and DTS-ES 6.1 Discrete.
DTS-ES Matrix can create a center rear channel from existing DTS 5.1 encoded
material, while DTS-ES 6.1 Discrete requires a specially encoded DTS-ES 6.1
DTS-HD Master Audio
This format uses lossless compression to create a "core" and "extension"
delivery system for systems equipped to decode it. It reverts to lossy
compression if the playback system does not include a Master Audio decoder.
Dual Mono Power Amplifier
A dual mono power amplifier is essentially two
separate amplifiers in a single chassis. This design achieves better separation
between channels, resulting in superior stereo imaging and greater dynamic
control. The most expensive examples incorporate separate transformers for each
channel. However, many models employ a high-efficiency toroidal transformer with
dual windings (one for each channel) and completely isolate the rest of the
circuitry for each channel.
Dubbing Stage A
specially designed room resembling a combined small movie theater and recording
studio control room. Dubbing stages are used by film directors and sound
engineers to create film soundtracks. A dubbing stage's audio characteristics
are defined by SMPTE standard # 202 and match those of SMPTE-standardized movie
theaters so that filmmakers will be able to accurately hear how their films will
sound when shown to the public.
(Digital Video) A format is used by many digital camcorders, DV is
usually recorded onto Mini DV cassettes. The DV format is memory-intensive even
though it employs a form of real-time lossy video compression. A DV clip
requires roughly 1 GB of storage for every five minutes of video. (Clips usually
are stored on the computer as QuickTime or .avi files.) DV uses "intraframe"
compression to encode video at 30 frames/second, thus making it edit-friendly.
This is in contrast to the more problematic "interframe" compression,
which is based on MPEG1 or MPEG2 codecs and makes editing more difficult because
it reduces the number of full frames/second. DV can provide a clean image with
up to 520 lines of resolution.
(Digital Versatile Disc) DVDs can store video, audio, still
image, or computer data.
A largely historic high-resolution audio format based on the very large storage
capacity of the DVD disc. It offers 5.1 and 7.1 channels (the .1 is for subwoofer) and digital
audio specifications of signals including 16/20/24-bit with 44.1/48/96/192kHz sampling rate. This format also
includes Dolby AC-3, linear PCM, and MPEG-2.
DVD Forum An
industry group of over forty manufacturers and technology providers that
oversees development and implementation of the technical standards for DVD
hardware and software.
The most common, virtually universal recordable DVD format. It is a write-once
format, much like the CD-R, that cannot be erased or changed once it is
recorded. DVD-R discs have to be finalized at the end of a recording session
before they are playable in another DVD player.
A record-once DVD format introduced and backed by Philips and adopted by the
other DVD+RW proponents. It promised easier use than DVD-R and was still
playable in most current DVD players. DVD+R discs need to be finalized before
they can play in another DVD player.
double-layer version of a DVD-R. Rarely used today.
DVD+R DL Essentially
the same as DVD+R except for extended recording capability thanks to its
double-layer (DL) structure. The physical differences between DVD+R and DVD+R DL
discs may cause some compatibility issues.
The DVD equivalent of the rewriteable CD-RW.
is a rewritable DVD format backed by Philips, Yamaha, HP, Ricoh, Thomson (RCA),
Mitsubishi, APEX, and Sony, among others. DVD+RW claims greater compatibility
than DVD-RW with most DVD players. The DVD+RW format is also easier to use in
that DVD+RW discs are finalized during recording rather than requiring a
separate step at the end of the recording session.
accurately known as DVD—Random Access Memory, DVD-RAM is a rewritable format
originally promoted by Panasonic, Toshiba, and other companies. It is not
playback-compatible with most standard DVD players or computer-based DVD-ROM
drives. It does, however, allow on-disc editing.
DVD Regional Codes
A DVD coding system enforced by the movie industry that is intended to preserve
movie distribution rights and agreements. See the chapter on DVD for more
for Digital Visual Interface, an increasingly rare video-only format for
connecting a source component to a video display. Now largely supplanted by HDMI
Short for Digital Video Recorder, a device for recording video programs directly
to a hard drive for later playback. DVRs are usually contained in cable and
satellite set-top boxes.
Usually specified in decibels, dynamic headroom is a measure of an amplifier's
ability to generate a significantly higher power level for short periods of time
in order to accommodate musical peaks or extreme sound effects. A 3 dB dynamic
headroom measurement indicates that the amplifier is able to generate twice the
rated power for that brief interval.
The difference, expressed in dB, between the softest and loudest sounds a particular
component, system, or medium can process without adding excessive distortion or
having the signal "buried" in a residual noise floor. Related to signal-to-noise
Dynamic Range Compression
Refers to a number of different technologies aimed at changing the relationship
between the loudest and quietest parts of a soundtrack so that explosions, for
example, are not as loud as they might otherwise be if uncompressed, and soft
dialog is more easily heard because it is louder than it would be if the signal
were not compressed. Usually reserved for so-called "late-night watching."
Any loudspeaker that uses dynamic drivers. (See also: moving