70 volt line See: constant-voltage
sample rate conversion The process of converting one sample
rate to another, e.g. 44.1 kHz to 48 kHz. Necessary for the communication
and synchronization of dissimilar digital audio devices, e.g., digital
tape machines to CD mastering machines.
sample-and-hold (S/H) A circuit which captures and holds
an analog signal for a finite period of time. The input S/H proceeds
the A/D converter, allowing time for
conversion. The output S/H follows the D/A
converter, smoothing glitches.
A theorem stating that a bandlimited continuous waveform may
be represented by a series of discrete samples if the sampling frequency
is at least twice the highest frequency contained in the waveform.
sampling frequency or sampling
rate The frequency or rate at which an analog signal is sampled
or converted into digital data. Expressed in Hertz (cycles per second).
For example, compact disc sampling rate is 44,100 samples per second
or 44.1 kHz, however in pro audio other rates exist: common examples
being 32kHz, 48kHz, and 50kHz. [Historical note re 44.1kHz vs.
44.056kHz: Since the first commercial digital audio recorders used
a standard helical scan video recorder for storage, there had to
be a fixed relationship between sampling frequency and horizontal
video frequency, so these frequencies could be derived from the
same master clock by frequency division. For the NTSC 525-line TV
system, a sampling frequency of 44,055.94 Hz was selected, whereas
for the PAL 625-line system, a frequency of 44,100 Hz was chosen.
The 0.1% difference shows up as an imperceptible pitch shift.]
sampling The process of representing the amplitude of a
signal at a particular point in time.
SAR (successive approximation register) A type of
analog-to-digital converter using a digital-to-analog converter
to determine the output word successively, bit by bit.
SCMS (pronounced "scums") (serial copy management
system) The copy protection scheme applied to consumer digital
recording equipment - it does not apply to professional machines.
This standard allows unlimited analog-to-digital copies, but only
one digital-to-digital copy. This is done by two control bits (the
C and L bits) contained within the digital
SCSI port (pronounced "scuzzy") (small computer
system interface) A standard 8-bit parallel interface used
to connect up to seven peripherals, such as connecting a CD-ROM
player or document scanner to a microcomputer.
SD (super density compact disc) See: DVD
SDDS (Sony Dynamic Digital Sound) Sony's
competing format for the digital soundtrack system for motion picture
playback. The signal is optically printed outside the sprocket
holes, along both sides of the print. Sony recently developed a
single camera system that records all three digital formats (Dolby
Digital, DTS & SDDS) on a single
inventory print, thus setting the stage for long term coexistence
of all formats.
SDIF (Sony digital interface format) Sony's
professional digital audio interface utilizing two BNC-type
connectors, one for each audio channel, and a separate BNC-type
connector for word synchronization, common to both channels. All
interconnection is done using unbalanced 75 ohm coaxial cable of
the exact same length (to preserve synchronization), and is not
intended for long distances.
SECAM (Sestem En Couleur Avec Memoire - "Sequential Color with
Memory") The analog video standard used for television broadcast
and composite video connections in France, former French colonies in
the Middle East an Africa, and in former communist countries
throughout most of Eastern Europe. SECAM was introduced in the
early 1960's an first adopted in 1967 in France. SECAM signals encode the video
as 625 horizontal lines of pixels scanned in odd and even sets at 1
Field (1/2 frame) every 50th of a second (to work with the European
power standard of 50cps), resulting in am effective video frame rate
of 25fps. Because of its similarity with PAL (same resolution, same
frame rate and same bandwidth), all of the modern video systems,
such as DVD, VCD and SuperVHS use PAL internally (for storing the
data in the storage media, etc) and just change the color encoding
to SECAM when set to output the signal back to a SECAM TV or
monitor. SECAM is one of three main television standards throughout
the world. See PAL and NTSC
semitone Music. An interval equal to a half tone
in the standard diatonic scale. Also
called half step, half tone.
serial interface A connection
which allows transmission of only one bit at a time. An example
in the PC world is a RS-232 port, primarily
used for modems and mice. A serial interface transmits each bit
in a word in sequence over one communication link. See also: parallel
servo-loop; -locked loop; -mechanism
A self-regulating feedback system or mechanism. Typically a feedback
system consisting of a sensing element, an amplifier, and a (servo)motor,
used in the automatic control of a mechanical device (such as a
loudspeaker). In audio, usually the name applies to a class of electronic
control circuits comprised of an amplifier and a feedback path from
the output signal which is compared with a reference signal. This
topology creates an error signal that is the difference between
the reference and the output signal. The error signal causes the
output to do whatever is necessary to reduce the error to zero.
A loudspeaker system with motional feedback is such a system.
A sensor is attached to the speaker cone and provides a feedback
signal that is compared against the driving signal to create more
accurate control of the loudspeaker. Another example is Rane's servo-locked
limiter which is an audio peak limiter circuit where the
output is compared against a reference signal (the threshold
setting) creating an error signal that reduces the gain of the
circuit until the error is zero.
servo-locked limiter Rane Corporation trademark for
their proprietary limiter circuit. See:
Claude E. (1916- ) American mathematician and physicist
who is credited as the father of information theory. In his master's
thesis Shannon showed how an algebra invented by the British mathematician
George Boole in the mid-1800s could represent
the workings of switches and relays in electronic circuits. His
paper has been called "possibly the most important master's
thesis in the century."
shelving response Term used
to describe a flat (or shelf) end-band shape when applied to program
equalization. Also known as bass and treble tone control
sibilant Linguistics. adj.
Of, characterized by, or producing a hissing sound like that
of (s) or (sh): the sibilant consonants; a sibilant bird call.
A sibilant speech sound, such as English (s), (sh), (z), or
SID (slew-induced distortion) See: DIM/TIM
sigma-delta See: delta-sigma
signal-to-noise ratio See: S/N
sine Abbr. sin Mathematics. 1.
The ordinate of the endpoint of an
arc of a unit circle centered at the origin of a Cartesian
coordinate system, the arc being of length x and measured
counterclockwise from the point (1, 0) if x is positive or
clockwise if x is negative. 2. In a right triangle,
the ratio of the length of the side opposite an acute angle to the
length of the hypotenuse.
sine curve Mathematics.
The graph of the equation y = sin x. Also called sinusoid.
sine wave Physics. A waveform
with deviation that can be graphically expressed as the sine curve.
sinusoid Mathematics. See: sine
slew rate 1. The term used to define
the maximum rate of change of an amplifier's output voltage with
respect to its input voltage. In essence, slew rate is a
measure of an amplifier's ability to follow its input signal. It
is measured by applying a large amplitude step function (a
signal starting at 0 volts and "instantaneously" jumping
to some large level [without overshoot or ringing], creating a step-like
look on an oscilloscope) to the amplifier under test and measuring
the slope of the output waveform. For a "perfect" step
input (i.e., one with a rise time at least 100 times faster than
the amplifier under test), the output will not be vertical; it will
exhibit a pronounced slope. The slope is caused by the amplifier
having a finite amount of current available to charge and discharge
its internal compensation capacitor. 2. Mathematics. Slew
rate is defined to be the maximum derivative of the output voltage
with respect to time. That is, it is a measure of the worst case
delta change of voltage over a delta change in time, or the rate-of-change
of the voltage vs. time. For sinusoidal signals (audio),
this equals 2 pi times the maximum frequency,
times the maximum peak output voltage: SR = (2 pi) (Fmax) (Vpeak).
smoke From the phlogiston
theory of electronics, it is smoke that makes ICs and transistors
work. The proof of this is self-evident because everytime you let
the smoke out of an IC or transistor it stops working -- elementary.
This has been verified through exhaustive testing, particularly
regarding power amplifier ICs and transistors. (Incidently wires
carry smoke from one device to another.) [Origin unknown but classic.]
smoothing filter See: anti-imaging
SMPTE (pronounced "simty")
(Society of Motion Picture and Television Engineers) A
professional engineering society that, among other activities, helps
establish standards, including a time code standard used for synchronization.
(Simple Network Management Protocol) The most common
method by which network management applications can query a management
agent using a supoported MIB (Management Information Base). SNMP
operates at the OSI Application layer.
The IP (Internet Protocol)-based SNMP is the basis of most network
management software, to the extent that today the phrase "managed
device" implies SNMP compliance.
S/N or SNR (signal-to-noise ratio)
An audio measurement of the residual noise of a unit, stated as
the ratio of signal level (or power) to noise level (or power),
normally expressed in decibels. The "signal" reference
level must be stated. Typically this is either the expected nominal
operating level, say, +4 dBu for professional audio, or the maximum
output level, usually around +20 dBu. The noise is measured using
a true RMS type voltmeter over a specified
bandwidth, and sometimes using weighting
filters. All these thing must be stated for a S/N spec to have
meaning. Simply saying a unit has a SNR of 90 dB means nothing,
without giving the reference level, measurement bandwidth, and any
weighting filers. A system's maximum S/N is called the dynamic
Software Any program or routine ( such as an application,
system file or device driver) that furnishes instructions or data to
the computer for processing. These are the components of a
computer system that are logical, not physical (hardware).
Software is also sometimes misused to refer to video, photos, audio
and any other type of data that can be handled by the computer.
solo A term used in recording and live-sound
mixing to describe monitoring (via headphones) a single channel
without affecting the main outputs (see: PFL)
-- same as cueing; however, it can
also refer to certain console designs where it replaces the main
mix with the soloed channel (called destructive solo).
sone A subjective unit of loudness, as perceived by a person
with normal hearing, equal to the loudness of a pure tone having
a frequency of 1,000 hertz at 40 decibels sound pressure level.
sonorous 1. Having
or producing sound. 2. Having or producing a full, deep, or rich
sound 1.a. Vibrations transmitted through an elastic material
or a solid, liquid, or gas, with frequencies in the approximate
range of 20 to 20,000 hertz, capable of being detected by human
ears. Sound (in air) at a particular point is a rapid variation
in the air pressure around a steady-state value (atmospheric
pressure) - that is, sound is a disturbance in the surrounding
medium. b. Transmitted vibrations of any frequency. c. The sensation
stimulated in the ears by such vibrations in the air or other medium.
d. Such sensations considered as a group. 2. Auditory material
that is recorded, as for a movie. 3. Meaningless noise.
4. Music. A distinctive style, as of an orchestra or
sound off To express one's views vigorously: He was always
sounding off about his boss.
sound pressure The value of
the rapid variation in air pressure due to a sound wave, measured
in pascals, microbars,
or dynes - all used interchangeable, but
pascals is now the preferred term. Instantaneous sound
pressure is the peak value of the air pressure, often used in noise
control measurements. Effective sound pressure is the RMS
value of the instantaneous sound pressure taken at a point over
a period of time.
sound pressure level or SPL The
RMS sound pressure expressed in dB re 20
microPa (the lowest threshold of hearing for 1 kHz. [As points of
reference, 0 dB-SPL equals the threshold of hearing, while
140 dB-SPL equals irreparable hearing damage.] See: inverse
(Society of Professional Audio Recording Services) Founded
in 1979, a professional trade organization that unites the manufacturers
of audio recording equipment and providers of services, with the
users. Their goal is worldwide promotion of communication, education
and service among all those who make and use recording equipment.
Often confused with NARAS.
single-ended spatial enhancement technique developed by Desper Products,
Inc., a subsiderary of Spatializer Audio Labs, Inc. Widely licensed
in both the consumer audio and multimedia computing markets, the
Desper, or Spatializer process is normally used as a postprocessor.
The Spatializer technology manipulates the original signal
in a way which causes the listener to perceive a stereo image beyond
the boundaries of the two loudspeakers. It claims to place sounds
in front of the listener in an arc of 180 degrees, with excellent
imaging and fidelity.
digital interface format, also seen w/o slash as SPDIF)
A consumer version of the AES/EBU
digital audio interconnection standard based on coaxial cable and
SPL controller See: leveler
SPL See: sound pressure level
splitter An audio device used to
divide one input signal into two or more outputs. Typically this
type of unit has one input with 6-16 (or more) outputs, each with
a level control and often is unbalanced.
See: distribution amplifier
spooler Comes from the acronym SPOOL derived from Simultaneous
Peripheral Operation On-Line. A program or piece of hardware that
controls a buffer of data going to some output device, including
a printer or a screen. Spooling temporaily stores programs or program
outputs on magnetic tape, RAM or disks for output or processing.
And you thought you were done learning for the day -- HA!
SRS (Sound Retrieval
System) A stereo image enhancement scheme invented by Arnold
Klayman in the early '80s while working for Hughes Aircraft, and
since 1993, marketed by SRS Labs, Inc. A standalone spatial enhancement
scheme, SRS benefits from not requiring encoding of the signal,
but thus prevents the audio producer from determining the location
of individual sound effects. The results vary, being heavily dependent
upon the original stereo mix. The goal is to extend the sound field
well beyond the limitations of the loudspeakers, and make the overall
sound seem more expansive. The elimination of the sweet
spot is claimed.
Standards Uniform specifications to permit
interoperability between devices from different manufactures or
countries. Standards consist of guideline documentation that
reflects agreements on products, practices, or operations by
nationally or internationally recognized industrial, professional,
trade associations or governmental bodies. Note: This
concept applies to formal, approved standards, as contrasted to de
facto standards and proprietary standards, which are exceptions to
the rule.( i.e. anything Microsoft )
stereo 3-way, etc. See: active
Streaming Technology that is capable of playing
audio and/or video before the complete data file has had time to
subcode Non-audio digital data encoded on a CD
that contains definable information such as track number, times,
copy inhibit, copyright, etc.
subgroups See: groups
submix See: groups
subsonic Having a speed less
than that of sound in a designated medium. [Use infrasonic
if referring to frequencies below human hearing range.]
subtend 1. Mathematics. To
be opposite to and delimit: The side of a triangle subtends the
opposite angle. 2. To underlie so as to enclose or surround:
flowers subtended by leafy bracts.
Super Audio CD See: DSD
supersonic Having, caused by, or
relating to a speed greater than the speed of sound in a
given medium, especially air. [Use ultrasonic
if referring to frequencies above human hearing range.]
SVGA (Super Video Green ArraySuper
Video Graphics Array) A video graphics ddisplay mode
standard. referring to a video adapter capable of a resolution
of up to 800 by 600 pixels.
sweet spot Any location in a two
loudspeaker stereo playback system where the listerner is positioned
equidistant from each loudspeaker. The apex of all possible isosceles
(two equal sides) triangles formed by the loudspeakers and the listener.
In this sense, the sweet spot lies anywhere on the sweet
plane extending forward from the midpoint between the speakers.
symmetrical (reciprocal) response
Term used to describe the comparative shapes of the boost/cut
curves for variable equalizers. The cut curve exactly mirrors the
synchronous A transmission process where the bit rate of
the signal is fixed and synchronized to a master clock.
Audio Concepts) A private organization conducting audio
seminars and workshops, sponsored by several pro audio companies.