Файл: Sound Tech Terms Dictionary.pdf

U

U:  A term used to define the unit of height in a rack-mounted assembly.  A one-U device is

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” high (44mm).  A two-U device is twice as tall, etc.

UART:  Universal Asynchronous Receiver Transmitter.  An integrated circuit that carries out

the function of asynchronous, bi-directional communication between a microprocessor and a
serial interface.  In MIDI, it is a part of the interface that forms the link between the processor
and the MIDI sockets.

UHF:  Ultra High Frequency.  The band of television broadcast frequencies reserved by the

FCC for local and community-access stations, local weather services, stock reports, etc.; chan-
nels 14 and higher.  Compare with VHF.

ultrasonic:  Having frequencies above the normal range of human hearing, i.e., higher than

about 20kHz.

Ultra ATA:  See IDE.

Ultra-Stereo:  See stereo optical print.

U-Matic:  A video tape recorder format developed by Sony for professional use.  A   

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” helical

scan video cassette, it has become the world standard for industrial and semi-pro videotape
productions.  This machine is also used in conjunction with a Sony PCM 1610 or PCM 1630 en-
coder to record digital audio instead of video.

una corda:  One string.  Used in piano music to indicate the use of the soft pedal.  See tre corda.

unadvertised specials:  In film, sounds that appear on a track, but whose presence is not noted

on the cue sheet.

unbalanced lines:  Any transmission line in which the two conductors are at different poten-

tials with respect to ground.  In an unbalanced connection, the ground conductor does double-
duty, completing the electrical circuit and serving as a shield.  Compare with balanced line.

undermodulation:  A situation which occurs when the amplitude of a signal falls well below the

optimum level in a recording or broadcasting system, causing it to be masked by noise.  In
digital systems, undermodulation can lead to distortion.  See overmodulation.

underscore:  Music that provides atmospheric or emotional background to the primary dialog

or narration onscreen to emphasize the action.

unidirectional microphone:  Any microphone in which the pick-up pattern exhibits more sen-

sitivity to sounds approaching on-axis, i.e., any variation of the cardioid pattern, such as a su-
percardioid or hypercardioid.  See also directional microphone, omnidirectional microphone, polar pat-
tern.

unison:  Two notes, or musical lines, which have the same pitch.  Also used less precisely to in-

clude a musical line played or sung in octaves.

unit:  A single reel of edited mag film, corresponding to a given picture reel. The unit can be ei-

ther single-stripe or fullcoat, and will usually contain fill leader in order to maintain sync with the
picture reel.

U

unity gain:  A device which neither attenuates nor amplifies a signal.  Most signal processing

devices have unity gain, which means that they neither amplify sound nor cause insertion loss,
and therefore can be added into an audio system at various places without upsetting the over-
all gain of the system.

Universal System Exclusive:  A part of System-Exclusive which is intended for all equipment,

irrespective of manufacturer.  The message uses one of three particular ID numbers after the
SOX status byte:  125 is for non-commercial or academic use; 126 is for non-real-time use and
includes messages for MTC Set-Up, SDS, MIDI File Dump, Bulk Tuning, and GM; 127 is for
real-time use and includes MTC Full Message, User Bits, Show Control, Notation, Device Con-
trol, Machine Control, Single-Note Retuning messages, Master Balance, Master Volume, and
Real-Time MTC Cueing.

Unregistered Parameter Number (NRPN):  See Registered Parameter Number.

upbeat:  See beat.

update mode:  In console automation, the operating mode in which previously written automa-

tion data is read back to its respective input faders for alteration by the engineer.  The position
of each fader at the beginning of an update take is defined by the system as its null-point.  If the
engineer leaves these faders at their initial levels throughout the take, no data will be changed.
Any fader movement above or below a null point is read in dB, and that track’s data changed
to reflect the same dB change from the previously written signal level.  This updated data is
then stored for later use.

USB:  Universal Serial Bus.  The new slow-peripheral (i.e., keyboard, mouse) interface technol-

ogy from Apple Computer.

user bits:  (1) A group of 32 bits within the 80-bit SMPTE timecode message which is available to

users for their own purposes, such as recording tape identity numbers, dates, etc.  (2) Also, a
System-Exclusive message of the real-time type which implements the SMPTE timecode mes-
sage described in user bits.

UV-22:  See dither.

V

VA:  An expression of the work which can be performed by an electrical device, but which ig-

nores the inductance of the load.  It is related to the watt in that it is also the product of poten-
tial difference in voltage, (V) and current  in amperes (A), but it ignores the power factor inherent
in that unit.

valve:  (1) See tube.  (2) On musical instruments, a device for lengthening or shortening the air

path through the instrument, resulting in lower or higher pitched tones, respectively.  Valves
are typically depressed with the fingers, such as on a trumpet or French horn.

vamp:  In a performance of a song, the ending.  Either a continuing repetition of the last chorus

intended to be faded out during the mix, or a coda section with solo lines, leading to a hard
ending.  See outro.

variable area:  The most common type of optical soundtrack used in motion pictures.  The vari-

able area track is a transparent line in a black background.  The relative width of the transpar-
ent part is varied in accordance with the sound waveform.  Most movie soundtracks today
consist of two parallel variable area tracks, making possible the recording of stereophonic
sound.  See SVA.

variable-rate converter:  A new type of digital recording, marketed by Kinetix, which at-

tempts to provide very high resolution sound without resorting to a static increase in bit depth
and sampling rate.  Typical linear systems divide audio signals into equal quantums of ampli-
tude and equal quantums of time, producing serially correlated sampling errors, or, errors
which are necessarily related to one another and are, therefore, not only not random, and
therefore not mutually canceling, but potentially mutually reinforcing at specific bands within
the audio frequency, making them more noticeable.  Briefly, a variable-rate converter wobbles
at random between 44.1kHz and 48kHz to distribute the sampling errors over a wide fre-
quency range, with the general result that they are inaudible.  The Kinetix converter also ran-
domizes the quantization steps so that each successive sample is quantized differently.  This
renders quantization distortion is redistributed as (Gaussian) noise where it is shifted into the
15-18kHz range on output where it is unlikely to be audible.  Variable-rate converters provide
low bit-rates, do not require dither or compression, produce less background noise and distor-
tion, with increased the audibility of low-level signals and enhanced stereo imaging.  The
downside is that the variable clock frequency causes problems for interfacing to other digital
systems which is why the current Kinetix product includes its own recorder.

variation:  A musical form in which a theme is presented and then repeated in a succession of

different guises.  These may include retaining the harmonic structure, while elaborating or oth-
erwise varying the melody, changing the time signature and/or rhythmic framework, or using
new harmonies, such as substituting the minor for the major of the harmonic sequence.

varispeed:  A means of changing the speed at which a tape recorder runs in order to change

the pitch or duration of a tape recording.  Recently, this involves the use of a servo-controlled
capstan, and the speed may be varied by changing the reference frequency of the servo.

varispeed oscillator:  In tape recorders, an oscillator used to vary the frequency of the AC

driving an AC capstan motor and, hence, the tape speed.  Recorders whose capstans are driven
by DC motors often have DC voltage controls for varispeed operation.  These are often mis-
takenly called varispeed oscillators.

V

VCA:  Voltage-Controlled Amplifier.  A device that responds to a change in voltage at its con-

trol input by altering the gain of a signal being passed through it.  Also, the digital equivalent
of a VCA which is more properly called a DCA.

VCF:  Voltage-Controlled Filter.  A filter whose rolloff frequency can be changed by altering the

amount of voltage being sent to its control input.  Also, the digital equivalent of a VCF.

VCO:  Voltage-Controlled Oscillator.  An electronic oscillator whose output frequency is con-

trolled by the application of an external direct voltage.  VCOs are used extensively to generate
musical signals in synthesizers.  The ease by which their frequency can be controlled makes
them very suitable for frequency modulation and complex sound synthesis.  See DCO.

VCR:  Video Cassette Recorder.  A device for recording and replaying video signals on cas-

sette tape.  Cassette formats in current use are   

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”, 8mm,   

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”, Beta or VHS (consumer formats),

and   

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” U-Matic.  See also VTR.

VDP:  Video Disc Player.

velocity:  (1) A type of MIDI data (range 1 to 127) usually used to indicate how quickly a key

was pushed down (attack velocity) or allowed to rise (release velocity).  A Note-On message with
a velocity value of 0 is equivalent to a Note-Off message.  (2) The velocity of sound:  The speed
at which sound waves propagate.  The precise speed will depend on the density of the me-
dium through which the sound waves travel: in air, at sea level and at 0˚C with 30% relative
humidity, this is approximately 1088 ft/sec. (331.7 m/sec.)  At average room temperatures it is
slightly faster.

velocity compression:  Each MIDI Note-On message has a velocity value between 1-127.  The

velocity corresponds to how hard the key was struck.  In velocity scaling, (more accurately
called a velocity offset), a group of notes is selected for editing and then their velocities are all cut
or boosted in a linear manner:  e.g., with a scaling value of -20, three notes originally recorded
with velocities of 65, 91, and 37 would be set to play back with velocities of 45, 71, and 17, re-
spectively.  In velocity compression (sometimes called velocity scaling), the velocities are multi-
plied or divided by some factor so that the differences between them get larger or smaller.
With a compression value of 75%, for example, the same three notes would be played back
with velocities of 49, 68, and 28.  This means that the note with the largest starting velocity is
reduced the most, while soft notes play back closer to their original velocity, helping to keep
them audible.  Thus, compression is a better way to smooth out the transients in a passage that
were played too loudly, without changing the musical dynamics of the piece.

velocity crossfade:  The blending of multiple samples in varying proportions depending on key

velocity.  Sounds on samplers that are often programmed to use velocity crossfades include pi-
anos and other tuned percussion instruments whose timbre changes character markedly de-
pending on how hard a note is played.

velocity curve:  A map that translates incoming velocity values into other velocities in order to

alter the feel or response of a keyboard or tone module.  Some devices have a preset range of
velocity curves, and some allow users to program their own.

velocity offset:  See velocity compression.

velocity of sound:  See velocity(2).

V

velocity scaling:  See velocity compression.

velocity sensitivity:  A type of touch sensitivity in which the keyboard measures how fast each

key is descending.  Compare with pressure sensitivity.

velocity switching:  See cross-switching.

vestigial sideband:  In AM, whereby a portion of one sideband is suppressed.

VFO:  Variable Frequency Oscillator.  An oscillator used in the generation of electronic music

and for audio equipment test signals.  Often the VFO is a simple knob or wheel.  VCOs are a
subtype of VFO which are voltage-controllable.

VHF:  Very High Frequency.  Electromagnetic waves with frequencies between 30MHz-

300MHz.  The subrange of 88.1-108MHz is used for FM radio broadcasting in most countries.
In the U.S., channels 2-13 on most television sets.  Compare with UHF.

VHS:  Video Home System.  A domestic standard   

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” cassette format for making analog video

recordings.  The commercially more successful of two such systems which first appeared in the
early 1980’s, the other being Sony’s Betamax.  Both formats have been used as a medium for
recording digital audio data: Betamax in Sony’s PCM-F1 system, while the successor to VHS, S-
VHS is used in the ADAT digital multitrack system.

vibrato:  A slow pitch oscillation; a periodic change in frequency, often controlled by an LFO,

with a periodicity of less than 20Hz, most commonly about 5Hz-8Hz.  Vibrato is created in the
wave oscillator when a modulation signal is sent from an LFO into the frequency modulation in-
put of the oscillator.  In synthesizers, vibrato depth is the intensity of the effect, and vibrato delay
is the amount of time a note is set to sustain before the vibrato effect enters.  Compare with
tremolo.

Video-8:  A consumer video recording format which uses 8mm tape in a small cassette.  It was

developed for use in hand-held cameras and other portable equipment, but has also been
adopted for use in some digital audio systems, such as ADAM.

video black:  A video signal composed of all black, containing horizontal sync, vertical sync,

and color burst information.  Video black is used to pre-stripe video tape as the master clock
(35.8MHz for NTSC) for sound synchronization.  SMPTE timecode may be derived from the
color burst data.  Also called black-burst color signal, but video black is actually black in color.

video sync:  A subset of video black which does not necessarily contain color burst signal.  It

uses horizontal sync or vertical sync to provide a very stable video reference source.  The signal
is used to control the speed of the video machines, digital audio machines, and is used as a
timing reference to ensure accurate synchronization.  See master clock, word clock.

virtual track:  A synthesizer part, as opposed to a recording of an acoustical instrument.

vision mixer:  A device for mixing video signals from a number of sources.  The relative

amounts of the signals are controlled by faders, primarily for mixing the output of television
cameras.