Файл: Sound Tech Terms Dictionary.pdf

T

termination:  A transmission line is said to be terminated if it is connected to an impedance

equal to its characteristic impedance, i.e., the end of the line is connected to a load that
matches the impedance of the line.  Microphones should not be terminated because the ter-
mination load reduces the signal voltage level.  Also misused to indicate the proper resistance
to which an audio device is intended to be connected.  See impedance-matching.

tessitura:  The range of “comfortable” sounds of an instrument.

test tape:  See biased noise.

THD:  Total Harmonic Distortion.  An audio measurement specification used to determine

the accuracy with which a device can reproduce an input signal at its output.  THD describes
the cumulative level of the harmonic overtones that the device being tested adds to an input
sine wave.  THD+n is a specification that includes both harmonic distortion of the sine wave and
nonharmonic noise.

theme:  A musical idea or phrase that becomes an important motif throughout a score.

Thérémin:  An early electronic instrument which used heterodyning by one fixed RF oscillator

which was modulated by a hand and an antenna.  Audio-range frequencies were produced
by the sum and difference signals from this modulation, making the Thérémin a predecessor
to modern FM synthesis.  The instrument was monophonic and almost uncontrollably microto-
nal.

thermal capacity:  An unstandardized performance specification for an amplifier which de-

scribes its thermal headroom.  This is not particularly meaningful as amplifier thermal perform-
ance varies with the input test signal.  Also used as a synonym for thermal headroom.

thermal equilibrium:  The length of time it takes electronic circuitry to reach its steady-state

operating temperature.  For example, it takes about ten minutes for most audio equipment
to reach thermal equilibrium, and all components are stabilized as far as voltage, current and
temperature swings which occur at start-up having been attenuated.

thermal headroom:  A term which denotes the difference between the nominal operating

temperature of a power amplifier and the maximum temperature at which the amplifier will
continue operating, i.e., before its thermal protection circuitry will shut it down.

thermal noise:  See quiescent noise floor.

third:  The interval between a note and the one three scale steps above or below it: three half-

steps (minor third) or four half-steps (major third).

third harmonic distortion:  That part of harmonic distortion which represents only the third

harmonic (three times the fundamental frequency) of a sine wave input to an electronic device.
The third harmonic of any tone is musically an octave and a fifth above the original tone, and
is easily noticeable in the output.  For this reason, the MOL of analog tape recorders, for ex-
ample, is often specified as that level at which third harmonic distortion reaches 3%.

third-octave:  Short for one-third of an octave.  The usual bandwidth on the individual faders

on a graphic equalizer and graphic displays on most RTAs.  Also, the Q on narrowband filters is
usually one-third octave.

three-head:  A tape recorder with separate record, replay, and erase heads.

T

three-stripe:  See 3-track.

three-track mix:  See 3-track.

threshold:  The specific point in a range at which some process or effect occurs.  In an audio

signal, it is the lower limit in the dynamic range above which a device, such as a compressor,
limiter, or noise gate, will affect the incoming signal.  See also expander, gain-before-threshold.

threshold of hearing:  The lowest-level sound detectable by a listener with good hearing.

Defined as 0dB SPL and usually specified for a 3kHz tone since the human ear is most sensi-
tive in this frequency range.  See loudness, SPL, equal loudness curves.

throat:  The opening at which a driver attaches to a horn.  Or, the narrow end of the horn it-

self.

thumper:  A  low-frequency sine wave at around 30Hz, triggered by a noise gate keyed to a

click track. A thumper is used to give filmed dancers the beat of a song while recording sync
sound; the thumper is subsequently filtered out.

THX™:  A trademark for a special motion picture surround-sound specification developed by

Lucasfilm in collaboration with audio engineer Tomlinson Holman.  The acronym comes
from both the name of George Lucas’ first feature film, THX-1138 and also from the initials of
Tomlinson Holman eXperiment.  Only the loudspeaker crossover network is manufactured
by Lucasfilm; other components of the B-chain, including their placement and installation
must be approved before the theater can be designated as “THX approved.”  THX is a thea-
ter sound system specification, and as such does not involve any type of film audio format, as
does Dolby Digital™, nor does it indicate that any of the film sound was produced by Lucas-
film Ltd.

tie line:  A permanent, but undedicated, connection between two points some distance apart,

e.g., between a terminal box in the studio and the patchbay in the control room.

tie-tack microphone:  See Lavalier microphone.

tight:  (1) Low-frequency performance of a loudspeaker when relatively free of hangover.

Poorly damped systems are said to sound loose.  (2) A recording made using close miking.
Also called tight miking.

timbral interference cues:  The same as comb filtering.

timbre:  (1) The perceived quality of a sound, unrelated to pitch or amplitude.  Timbre is de-

termined by how many harmonics are present in the sound, their frequencies, and how loud
each is in relation to the fundamental frequency, and how the relative amplitudes of those
harmonics change over time.  The initial and ending transients of a tone have more to do
with the timbre of a tone than its harmonic content.  Also referred to as tone color.  (2) One of
the building blocks of a patch in a Roland synthesizer.

timbre envelope:  The change in the tone of an instrument over time.

timbre modulation:  A technique whereby a sample loop point length or position is changed

via modulation, such as sweeping through a wavetable to produce an extreme stuttering ef-
fect.

T

time alignment:  In a multiple-driver loudspeaker system, it is important that the time delay

of each driver and its associated crossover network be the same to preserve accurate transient
response, i.e., the high frequencies and low frequencies reach the listener’s ear at the same
time.  Crossover networks have different delays depending on the frequency range they
cover, as do speakers; woofers have more delay than tweeters.  One can place tweeters far-
ther from the listener, or build time-delay into the high-frequency signal path.  See transient
response.

time-base corrector (TBC):  An electronic device that repairs dropouts and other defects in the

synchronizing signals of a video picture, then acts as an outside sync reference to which play-
back machines can conform.

timecode:  A type of non-audio signal that contains information about elapsed time on a film,

tape, or disk recording.  Used for a synchronization reference when synchronizing two or
more machines such as sequencers, drum machines, and tape decks.  See SMPTE timecode,
MTC, FSK.

timecode generator:  An electronic device that produces SMPTE timecode signals, which can be

used to synchronize the frame rate of motion picture cameras and recorders, television cam-
eras, VTRs, VCRs, etc.

timecode regeneration:  The process of creating a new timecode based on an incoming time-

code signal or positional reference.  See dropout, freewheeling.

time-coherent:  A device is said to be time-coherent if it exhibits an essentially linear phase-

shift over frequency, i.e., the characteristics of a pure delay.  It is not necessary that the fre-
quency response be flat, just that the phase-shift vary linearly with frequency.  Apparently,
humans can hear time differences in the 5µs-10µs range.  A lack of time-coherency is usually
problematic in multi-way speaker systems and some microphones.  The crossover point in
multi-way loudspeakers, without careful control and compensation, causes the speaker to
output a multi-lobed pattern, i.e., the main energy output is not in front of the speaker, and
the polar pattern is asymmetric.  In a microphone, a perfect characteristic impulse response
would be where the diaphragm would cease moving as soon as the sound ended.  However,
bodies in motion tend to remain in motion; in addition, all of the microphone resonates, not
only the diaphragm.  All of this additional motion contributes to the coloration of the sound
by smearing the various arrival times of the various frequencies.  By using a very small,
lightweight diaphragm housed in a capsule that has a minimum of resonance and reflective
surfaces, coloration is reduced.

time masking:  See temporal masking.

time signature:  The meter of a work is indicated at the beginning by two numbers, one

above the other: the lower indicates the chosen unit of measurement (half-note, quarter-
note, etc.), while the upper indicates the number of such units which make up a measure.  In
simple times, such as   

2

4

,   

3

4

, and

4

4

, each beat is normally halved to form eighth-notes, etc.  In

compound times, such as   

6

8

,   

9

8

, or   

12

8

, the basic beat is grouped into threes to form dotted

notes.  In faster tempos, musicians can regard these dotted notes as the actual beat.  The time
signature,  , is called common time and indicates   

4

4

 time, while  , cut time, indicates the gener-

ally faster 

2

2

 time.

T

time-stretch:  To change the length of a sample without altering the pitch.  Compare with

pitch-shift.

timing clock:  See MIDI clock.

tip, ring, and sleeve:  See TRS.

TLA:  (1) Three Letter Acronym.  From NASA, a long time ago.  Modern usage is somewhat

disparaging, as the world is now speaking exclusively in TLAs.  (2) Transformer-Like Ampli-
fier.  A design for microphone preamplifier design by Rupert Neve which uses active compo-
nents to simulate the operational characteristics of conventional transformer coupling, but
with lower crosstalk.

TOC:  Table Of Contents.  The inner track of a CD, containing information about the disc

such as number of tracks, their position on the disc, timing, and disc ID number.

Todd-AO:  Todd-American Optical.  The 70mm widescreen process developed jointly by

Mike Todd and the American Optical Company.  Also the name of a film sound company in
Hollywood.

tonal:  Music that is written with a primary pitch, i.e., is written in a specific key, such as C, is

called tonal.  See tonic.

tone:  (1) Refers to a signal which has a particular and usually steady pitch.  The simplest of

tones are sine waves.  (2) Tone also refers to timbre, or quality of a musical sound, such as
“bright,” “mellow,” etc.  (3) A synonym for whole-step, an interval of two half-steps, e.g., from
C to D.  (4) A synonym for note, i.e., any particular sound.

tone color:  See timbre.

tone control:  One or more knobs on an audio amplifier or preamp which modify the rela-

tive balance between the treble and bass tones.  Tone controls are actually equalizers and they
change the frequency response curve of the device implementing them.

tone module:  See expander(2).

tonic:  The reference (lowest) pitch on which a musical scale is built, i.e., the “do” of do-re-mi.

It is defined in terms of the musical note rather than in terms of absolute frequency.  For ex-
ample, if one changes the key of a musical selection from C to A  this is a change of the tonic
from the note C to the note A .

top hat:  A plastic disc and a handle designed for placing over a tape pancake, taking the place

of the upper reel flange to allow smooth winding of the tape.  Also called a hat.

topping and tailing:  The process of removing extraneous sound at the beginning and end of

a song, any fades are added or adjusted, and running times are calculated for a master tape or
digital copy.

top sheet:  See binky.

Toslink:  See S/PDIF.

T

touch-sensitive:  Equipped with a sensing mechanism that responds to variations in key veloc-

ity or key pressure by sending out a corresponding control signal.  See aftertouch.

track:  (1) (verb) To be controlled by or follow in some proportional relationship, as when a

filter’s rolloff frequency tracks the keyboard, moving up or down depending on what note is
played.  (2) (noun) One of a number of independent memory areas in a sequencer.  By anal-
ogy with tape tracks, sequencer tracks are normally longitudinal with respect to time and
play back in sync with other tracks.  See channel.  (3) One of the longitudinal areas of a mag-
netic tape which is formed by recording an audio signal along it, separated by guardbands.  (4)
A section on a recording, containing a discrete song or other selection.

track-at-once:  A CD production method whereby one or more tracks is burnt at a time; a

link is written between the tracks.  This method is often used to create multisession CDs.  A
disadvantage of track-at-once recording is that gaps between tracks must be at least two sec-
onds in length.  Compare with disk-at-once.

tracking:  (1) The process of following the envelope of a signal’s waveform, as in a level meter

of any type.  (2)  In describing the performance of a phonograph stylus or other transducer,
the measure of it s ability to precisely follow the instantaneous waveform of the applied signal,
be it mechanical, e.g., a record groove, acoustic, or electrical.  (3) A synonym for over-dubbing.
(4) See double-tracking(1).

tracking error:  (1) Because the tonearm of a record player is pivoted at the stationary end,

the stylus moves across the record in an arc and meets the groove at an ever-changing angle.
The cutting stylus, however, moves in a straight line, always 90˚ to the groove direction.  This
condition is called tracking error.  (2) An error which occurs in disk drives when the
read/write head cannot be placed accurately over the data blocks due to a misalignment in
the head servo, a defect in the recording medium, or a misalignment in the recording process.
Also, a similar error in CD player mechanisms.

track laying:  (1) The process of recording audio signals to a track or tracks, either simulta-

neously or sequentially, prior to mixdown.  (2) The editing and assembly of the various tracks
of magnetic film containing dialogue, narration, sound effects, music, etc., in preparation for
re-recording, mixing, or dubbing.  Also called sound cutting.

track negative:  Film terminology for a soundtrack negative.

track select:  The process of enabling specific tape machine tracks for recording.

transaural audio:  The use of psychoacoustics to give the listener the illusion of sound coming

from all around, even though there are only two loudspeakers.  The listener must be posi-
tioned on the center line of the two speakers to correctly perceive the phantom images.  An ex-
ample is the QSound™ system.  Also called psychoacoustic surround-sound, or fifty-yard line
surround.

transducer:  A device which converts mechanical, magnetic, or acoustic energy into electrical

energy, or vice versa.  See DI, electroacoustic, electroacoustical transducer.