Файл: Sound Tech Terms Dictionary.pdf

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:  See Ohm.

OBU:  Outside Broadcast Unit.  A team of technicians responsible for recording or broadcast
away from a studio.

OCN:  See EK neg.

octave:  The logarithmic relation of sound frequencies used in most modern Western music.
The frequency of each higher octave is twice the preceding one, i.e., an octave is a frequency
ratio of 2:1.  An octave band consists of all the frequencies within an octave.  There is one octave
between 100Hz and 200Hz, also between 1kHz and 2kHz.  Octaves are perceived as equal
pitch intervals, even though the true bandwidth in Hertz varies with the frequency level of the
octave.  The name arises from the musical practice of defining the eight notes of the scale
within a doubling of the frequency.  To ears, two frequencies an octave apart sound like the
same note.

OE:  Operator Error.  A failure in any mechanical or electronic system caused by inappropriate
action on the part of the humans setting up or operating the system.

off-axis:  The opposite of on-axis.  (1) Not directly in front of a loudspeaker.  (2) Not within the
optimal acceptance angle of a microphone, and therefore not recorded at full level.  See direc-
tional microphone.

off-axis coloration:  A dull or colored effect on sound sources that are not placed within the
acceptance angle of the microphone.  To avoid off-axis coloration, place mics so that they are
aimed at sound sources that put out high frequencies, such as cymbals, when miking a large
source.  And, use a microphone that has a flat frequency response over the recording field, i.e.,
has similar polar patterns at midrange and high frequencies.  Most large-diaphragm mics have
more off-axis coloration than smaller mics (

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diaphragm or under).

offbeat:  See beat.

offlay:  To separate individual sound effects, pieces of dialog or other sounds originally on one
roll of magnetic film, placing each on a separate roll to allow for individual equalization or
other effects treatment.

off-line:  See on-line.

off-mic:  See off-axis.

offset:  (1) A time-difference correction made between two or more devices to achieve proper
synchronization.  For example, if a VCR and multitrack are 1.5 seconds out of sync, instructing
the synchronizer to calculate an offset for that amount could resync the sound and picture.  (2)
A correction that affects the onset of an event.  For example, a velocity curve offset defines a
threshold below which no velocity data is sent.  When the velocity value exceeds the thresh-
old, velocity response follows the selected curve.

ohm ( ):  A unit of electrical resistance or impedance, that which opposes an electric current in a
conductor.

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Ohm’s Law:  A basic law of electrical circuits, the mathematical relationship between electrical
voltage, current and resistance: the current in an electric conductor is directly proportional to the
voltage across it and inversely proportional to its resistance, i.e., the voltage and current in a
conductor exhibit a linear relationship.  It states that the current, I, in amperes in a circuit is
equal to the voltage, V, in volts divided by the resistance, R, in ohms:  thus, I=V/R.  Ohm’s law
works for DC, and for AC if the resistance is a pure resistance, but if the resistance has any re-
active components, inductance or capacitance, the current depends on the frequency as well as
the voltage.

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I

R

OMFI:  A file format first proposed by Avid to allow for digital audio data interchange among

digital dubbers, editorial workstations, and hard disk editors.

omnidirectional microphone:  A pressure operation microphone with a non-directional accep-
tance angle, i.e., one that is spherical, usually called an omni.  See directional microphone.

Omni Mode:  See MIDI Mode.

OMS:  Open Music System, formerly Opcode MIDI System.  A real-time MIDI operating sys-

tem for Macintosh and PC audio applications.  OMS allows communication between different
MIDI programs and hardware, so that a sequencer could interface with a librarian program to
display synthesizer patch names (rather than just numbers) in the sequencer’s editing win-
dows.

on-axis:  See off-axis.

on-board effects processor:  This can be used in a synthesizer to add reverb, chorusing, or other

effects.  On most synthesizers, it is possible to set the effect send level separately for each of the
multitimbral parts.  As opposed to outboard.

one-legged:  A term to describe a broken electrical connection.  In a balanced line connection, a
symptom is the loss of gain and low frequency content in the signal.  In an unbalanced line
connection, the signal will probably disappear altogether.  See also open circuit.

one-shot sampling:  A sound which is sampled once and then triggered as necessary.

one to one:  See 1:1.

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on-line/off-line:  (1) The opposite of real-time, i.e., processing to an audio or other file which
is not done at the same time as the human actions which initiate the processing.  (2) In the
videotape editing process, off-line is when the final edit list is compiled on a less expensive
machine, i.e.,  where the EDL is created, but not conformed, in preparation for the final edit.
On-line is where the video tape master is created from the EDL, including all effects using
high-quality equipment, usually a 1” video deck.  (3) In a network, any device which is
able/unable to receive or transmit a signal.  (4) In a system of synchronized devices, a slave
device which is waiting for a particular timecode value to be reached before it will play or re-
cord, etc., is said to be on-line.

opamp:  Operational amplifier.  A differential amplifier with extremely high input impedance and
high gain.  Its characteristics can be tailored to various amplification tasks by the application of
proper feedback to produce various effects, but is characterized by a low, ground-referenced
output impedance.

open air acoustic:  In a studio, the simulation of open air acoustic is achieved by the use of

screens to surround the sound source and a microphone.  This ensures that much of the sound
energy which travels away from the microphone is absorbed and is not reflected back to it.
This absence of reflection makes the sound appear to be located outside.

open circuit:  A circuit through which an electrical current cannot flow, perhaps because a
component has failed or a connection has been broken.  See also one-legged, short circuit.

open-circuit voltage rating:  The output voltage of a microphone with no load, i.e., with infi-

nite resistance such as in an open circuit, or when driving a resistive load at least twenty times
the microphone’s internal impedance.  One of the standard specifications of microphones.

open-loop:  An amplifier without feedback is said to be in an open-loop mode, or to be an open-
loop amplifier.  The feedback around the amplifier closes the loop.

open-reel:  A type of tape machine which uses tape wound on spools, rather than tape which

is sealed in a cassette.

open track:  On a multitrack tape, any track that has not yet been used, or that may be erased
and reused for overdubs.

operating level:  The voltage level defined for any audio system at its nominal, 100% modula-
tion level, not including any headroom.  Usually defined as 0dBVU for a steady sine wave.

operator:  (1) A term used in Yamaha’s FM synthesizers to refer to the software equivalent of
an oscillator, envelope generator, or envelope-controlled amplifier.  (2) The general term for a
structural component of FM synthesis, analogous to an oscillator/envelope/amplifier in
synthesizer parlance.

optical disc (OD):  A very dense type of digital data storage medium.  The data are encoded in

a spiraling pattern by a laser that carves tiny pits into the surface of the OD master, every
change from land to a pit indicating a change from a 1 to a 0, or vice versa.  Where no change is
recorded, the last-read digit is indicated for each increment of groove length.  In the reproduc-
tion device, a small laser scans the groove, reading the changes from land to pits, converting
this information back into data.  The data can be text, video, or digital audio, such as CDs and
laserdiscs.  See LIMDOW.

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optical recording:  Sound recording on film.  The photographically printed film soundtrack is
known as the optical track.  See SVA, variable area.

opticals:  (1) Effects on 35mm film that are made in an optical printer, such as dissolves, fades,
super-impositions, freeze-frames, matte shots, etc.  (2) Loosely, any effect used in a film or
video production.

optical sound:  The type of sound reproduction on film that employs a photographic printing
process of the optical track.  As opposed to magnetic film.  See optical recording.

optical track:  A method of recording an audio signal in the emulsion of a film alongside, and
in sync with, the picture frames.  The photographically printed film soundtrack that appears
either between one row of perforations and the picture in an answer or release print (in 35mm),
or along the edge of the print opposite that with the perforations (in 16mm).  The track area on
a 35mm print takes up a total width of 100 mils, which, being one-tenth of the space between
the sprocket holes, displaces the centerline of the image on the film by 50 mils, hence called the
Academy centerline.  See DES.  (2) The master or original photographic soundtrack made di-
rectly from the mono mix or 35mm three-track mix.  This strip of film has no video image, but is
printed along with A- and B-rolls onto the composite answer print or release print.  The track
can be a negative or positive image, depending on the type of camera and print stock.  See also
stereo optical print, 50% level.

opto-electric:  A device which uses a variation in light intensity to cause a change in electrical
current.  Variable photoresistors are sometimes used as gain control elements in compressors
where the side-chain signal modulates the light intensity.

opto-isolator:  An electronic component that can pass a signal via a light path, avoiding a di-
rect electrical connection between two separate circuits.  This will prevent voltage spikes gen-
erated in one piece of equipment from damaging another unit in the network, as well as
breaking ground loops.  The unit consists of a light source (an LED) and a light detector (a pho-
totransistor) enclosed in a sealed box, the whole package looking IC-like.  The part of the MIDI
specification that deals with hardware requires that all MIDI In connections use an opto-isola-
tor.

ORC:  Optical Radiation Corporation.  See Cinema Digital Sound.

order:  In discussing filters, the number of poles a certain filter possesses is called the order of

the filter.  Thus a T-section is a third-order filter and an L-section is a second-order filter, etc.
The slope, in dB/octave, of the filter response in its stopband is equal to six times the order.

ORTF:  Office de Radiodiffusion-Television Française.  A stereo microphone configuration de-
signed by the French national broadcasting system.  This method calls for two cardioid micro-
phones to be spaced 17cm (6.7”)  apart, at an angle of 110˚.  The 17cm represents normal ear
spacing, and the 110˚ is to simulate the directional pattern of the ears.  Recordings made using
the ORTF method sound more open and spacious than those produced by the X-Y miking
method.  ORTF works well with headphone applications, but tends to sound somewhat dry
and lacking in warmth due to the directional patterns of the cardioids, which pick up little am-
bient room sound.  However, because of the close spacing of the microphones and the resultant
similarity in phase, ORTF does provide mono compatibility, desirable in broadcasting.  The
Swedish equivalent is NOS, which is the same, except that the angle is 90˚ with a spacing of
30cm (11.8”).

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oscillator:  (1) An electronic device which generates a periodic signal of a particular frequency,
usually a sine wave, but sometimes a square wave or other waveform.  In an analog synthesizer,
oscillators typically produce regularly repeating fluctuations in voltage--that is, they oscillate.
(2) In a digital synthesis, an oscillator more typically plays back a complex waveform by
reading the numbers in a wavetable.  An oscillator allows a choice of pitch and waveform, the
first affects the perceived musical pitch and the second affects the timbre.  Additional parame-
ters that are almost always found in the oscillator section of a synthesizer are those that deal
with vibrato and pitch-bend.

oscillator sync:  A sound synthesis technique whereby one oscillator’s cycle is synchronized to

that of a second.  This forces the waveform of the slave oscillator to restart its cycle each time the
master crosses the zero-point.  As a result, the fundamental of the slave is the same as the master,
but the waveform is radically changed.  The pitch of the controlling oscillator is not normally
added into the audio mix, but can be shifted by pitch-bend, envelope, aftertouch or an LFO, pro-
ducing substantial changes to the harmonic content of the slave oscillator, but without changing
the fundamental pitch as does ring modulation.  Instead, the higher harmonics around the pitch
of the slaved oscillator are emphasized, producing a very hard edge to the tone.

ossia:  Italian for “or.”  Usually used to indicate an alternative version of a musical passage.

ostinato:  Italian for “obstinate.”  A short melodic and/or rhythmic idea which is continually
repeated, often in the bass.  Known as a riff in popular music.

outboard:  In a recording studio, special equipment such as effects devices and power amplifi-

ers that are not included within the recording console are called outboard devices.  Compare
with on-board.

out-of-phase:  A condition where two signals have a phase difference of 180˚, or one-half cycle.
It should be called out of polarity, phase being a continuous variable rather than discrete.  The
same as antiphase.  See phase reversal.

output:  The point of exit of a signal from a system, e.g., a section in a mixer or other device
where the signal is transmitted to a device external to the mixer, such as an effects processor,
headphones, or monitors.

output impedance:  The output impedance of a device is the actual impedance at the source
output terminals.  See impedance-matching.

output level:  See nominal level.

output point:  See channel insert.

output power:  The lower level that a system outputs under a specified load.  Expressed in VA
or RMS (watts).  See also power bandwidth, rated load.

outro:  A term derived from intro and which refers to a section at the end of a piece of music;

used in popular music in preference to the classical term coda.  It leads to or replaces, in the
case of a fade-out, a definite ending.  See vamp.

out-take:  Any take produced in a recording session which is not used in the final master.