Файл: Sound Tech Terms Dictionary.pdf

Introduction

This dictionary was born in Scotland in the spring of 1996 and represents my mid-life opus. Yielding to the typical mid-life crisis seemed both

unimaginative and self-indulgent. My motivation for writing a dictionary was that I was entering my third score of life and it was time for a career change; I

do this every twenty years whether I need to or not. A dictionary appealed as it’s one thing to peruse the technical journals, but another to actually

understand them. Having done the go-learn-everything-about-the-new-career-so-I-don’t-look-like-a-total-idiot thing before, I knew that the hardest thing to

do is explain something you don’t really understand to someone else. This dictionary was my imaginary audio friend (in the wilds of Scotland, company

is hard to come by.) 

As with my other successes in life, such that they are, next to my aunts I owe the greatest debt of thanks to Len. Monica Anderson was my first (real)

audio friend, although she and I have been friends for years. Monica helped me put together my first very own project studio and has graciously accepted, if

not actually read, drafts of this dictionary. If I had known about Godrick Wilkie’s book, I probably wouldn’t have gone through this exercise, but it’s

better that I didn’t and I did because he’s English and it’s very true about two cultures separated by a common language. The most awe-inspiring treatise

in audio I’ve come across is the book by Glenn D. White; it’s a good complement to the Wilkie book because the first is too simple, and the latter quite

rigorous. I have tried to tread midway between the two. Tell me if I’ve strayed from the path. 

I also owe thanks to my favorite musicians: Karen Bentley, Dimitry Cogan, Dennis James, Viviana Guzman, and Jonathan Salzedo et al. for letting me

record them and get a practical understanding of what this all means. I found audio engineering to be just like programming; it’s great to read all the

books, but it really doesn’t make any sense until you get your hands dirty and, in this case, trip over the mic cables. 

A few notes on the structure of the dictionary: In alphabetizing the words, I have ignored symbols in the middle of words, for example “deemphasis.” This

is because of the utter lack of standardization in spelling technical words, i.e., optional hyphens, spaces, or other non-alphanumeric characters. If you don’t

see it, be creative and look around. If you still can’t find it, 

send me mail

. Also, whether a term is listed completely spelled out or under its acronym

is pretty arbitrary. In general, I listed it the way I most often see it used, e.g., DAT is listed under DAT, not digital audio tape. Again, look around. If

that doesn’t work, complain. 

I have chosen to italicize words used in definitions which appear elsewhere in the dictionary. Italics seemed less obtrusive than bold or SMALL CAPS.

However, I haven’t italicized every word that is defined (frequency, for example, occurs in about every other sentence), but only the first instance in a

definition, and then only when useful for understanding the current context. Occasionally, italics are used to just set off a term, such as “This is called the

quadratic residue sequence” or, “those wires are called legs.” distinctly from the rest of the text. This only happens about six places in the dictionary; I did

it because it seemed distracting to put the terms in quotes, like they weren’t really words. You’ll know you’ve found one of these when you go to look it

up and it’s not defined. (If really need to know all about the quadratic residue sequence, (1) you probably already know, and (2) w.l.o.g., you will be

happier with the White book; and (3) legs are, well, legs.) 

At the end of many of the definitions there will be a “See” or “See also.” These additional terms are not listed in any particular order; the dictionary has

been an evolutionary process and I just add the new terms as I find them and have never gone back to reorder them alphabetically, by relevancy to the

current word, or by any other heuristic. I’ve tried to make sure that all related terms are included where necessary for context or completeness; please let me

know if I’m missed some. Reading a dictionary, even one’s own, can get a little tedious. I’ve read this one completely seven times now. It used to take

exactly the same length of time the train took from London to Edinburgh. I’d probably have to go to Istanbul now to do it in one train ride. From

Virginia. 

Sometimes the definition of one term is so inexplicably intertwined with another that it didn’t make sense to separate them, even if the alphabet did, so I

didn’t. When this happened, I would just cross-reference one term, arbitrarily, and make a combined definition in one place. An example of this is direct

sound(1). Sometimes things seem obvious, e.g., opposite of passive is active. But then the opposite of outboard isn’t inboard, it’s onboard, complete

with hyphen; the opposite of boost isn’t squash, it’s cut. So, if a few things seem to have the “duh syndrome,” I tried to err on the side of completeness. 

Sometimes the choice of main definition is pretty arbitrary, usually where there are two or more terms in common use, such as production sound and

location sound. Sometimes the reason for the choice is completely non-obvious as in rolloff frequency vs. cutoff frequency. In this case, I have deliberately

chosen a term which may not be the most commonly used. I picked the former as there is almost never a slope parameter that is actually a cutoff, only in

the case of a limiter. The slope almost always is, in fact, a rolloff and it seemed better to use that term as it more closely matched what is actually

happening, rather than subscribing mindlessly to “Better Tomes and Jargon.” There are actually four terms in common use which describe filter slope: the

two mentioned above, besides critical frequency and corner frequency. They are all reasonable; pick the one you like--I did. And, the use of any term varies

among practitioners, by specific field within audio or by location. I realized early on that there was no way to please all of the noise nerds all of the time... 

And, being me, I left out most of the computer terms. I assumed that this dictionary would be (uniquely) useful to those of the digital persuasion, i.e.,

those of us with weak musical and/or MIDI backgrounds, but who are very strong on acronyms. I hope I didn’t get too EE-bound. In my short tenure as a

recordist/mixing engineer, I appreciate how important it is to actually understand about balanced lines and ground loops, especially when it becomes

appallingly clear that the well-meaning volunteer who cut the ground wire at the service panel to eliminate the hum from the church PA system did not

have my $8,000, 24-bit A/D in mind. Again, complain, but gently. 

For the more musical, I would appreciate input on what I’ve left out musically, but also what I’ve neglected to define in the technical forest that has made

things more difficult for you in trying to use the dictionary. One really finds out who one’s friends really are when one asks them to read draft copies of

one’s dictionary. I’m not exactly friendless, but it’s getting very close. 

In keeping with my anarchistic view of the universe, there is also no particular rule for inclusion of detailed data other than what would be useful in the

field. I did not include all MIDI notes and commands as one is likely to be somewhere quiet with a bookshelf when one needs that, and, I know that

everyone, but everyone, takes the manuals for their synths and samplers along to every gig, right? The charts on dB, information on AC, pin-outs, etc. I

thought might be needed in the field (read this: I’ve needed it), and it would be handy to have this information in one, portable source. Again, comments

welcome. 

Finally, in response to almost universal feedback that DD should be published (which is probably more the issue that not everyone wants to sit in the

wilds of Scotland, writing dictionaries): I don’t want to spend any more time on this dictionary; it’s accomplished its purpose, i.e., I can now read the

trade press. And, as I said, I’m running out of friends. I welcome comments on alternate definitions, things I forgot, things which are unclear. Be kind:

this nanoscopic contribution to better global karma has had a gestation of over two years of my life. 

Sandy Lerner,

Sono Luminus

1997, 1999

A

1:1:  One to one. In standard usage, a copy of the edited worktrack copied onto another roll of
striped mag film so that sound editors and mixers will have access to the worktrack.  In gen-
eral, however, it denotes any single-track-to-single-track copy, and thus has variants 3:3, 4:4,
etc.

3:1 rule:  A rule for microphone placement:  space microphones at least three times the mic-
to-source distance.  For example, if two mics are each placed one foot from their sound
sources, they should be at least three feet apart.  This method prevents the blurred, colored
sound caused by phase cancellation between microphones.

3-stripe:  See 3-track.

3-track:  A mix of all the soundtracks of a film, in which the sounds are divided into the DME
stems, each stem recorded on a separate stripe along the width of the 35mm magnetic film.
Also called three-stripe.

4+2:  Four Plus Two.  Film sound slang for a 6-track element (usually mag film) that contains
a 4-track M&E, one track of material for a foreign-language mix, and one track of original
dialog as a reference.

4:2:4:  See Dolby ProLogic™.

4-track:  A film soundtrack format used for overseas markets.  Called a completely filled mix, the
four-track stereo M&E mix is ready for the addition of dubbed languages.  The M&E tracks
should include background sound effects and room tone for every scene, i.e., all sound ex-
cept dialog.

50% level:  The standard reference level for optical sound recordings that corresponds to the
width of the track at 50% modulation, or at 6dB below clipping.  In practice, there is about
2dB headroom available, if all of the recording/playback heads are perfectly aligned.

5.1-channel format:  A digital, discrete six-channel mix of Left/Center/Right/Left Sur-
round/Right Surround/subwoofer mix.  5.1 is not a specific surround format tied to any
particular company or codec.  However, all the hardware is the same for any 5.1-based system
except for the codec.  It is planned that CDs, laserdiscs, and DVDs will have an ID flag to let
the decoder know which codec was used, enabling decoders to recognize all incoming bit-
streams and automatically switch modes and process the incoming signal appropriately.  It is
a listening platform and hardware concept for a surround loudspeaker system.  See DTS,
Dolby Digital, HDTV, CDS, LFE.

5-2-5 matrix:  See Logic 7.

70mm:  See film.

7.1 Split-Surround:  The additional two speakers are employed at the front of the soundstage
to deliver more uniform sound in wide-format theaters of screen widths of up to 60’ or more,
where there might be seats with hole-in-the-middle in between the C-L, and C-R channels.  See
SDDS.

A

85:  A common SPL level reference in the film audio business, which is found by setting the
SPL of pink noise is sent through one speaker (L, C. or R) at 0VU (analog) bus level, which is
the equivalent of –20dBFS in digital recording.  Measurement is made at the console, with an
SPL meter set to C-weighting and the meter ballistics set to slow response.

88:  The SPL for Dolby Stereo SR films.  If a film has been monitored at 85 during the final mix,
the stems will be lowered 3dB each when making an SR Lt-Rt printmaster to accommodate the
increased gain from summing the stems.

A:  The left-hand part of a stereo signal.

A-2:  See Voice of the Theater.

A-3:  Dolby laboratories low-bit-rate codec system used in its Dolby Digital format film, in both
broadcast and consumer video formats.

A-4:  See Voice of the Theater.

A-7:  See Voice of the Theater.

A440:  See concert pitch.

AAC:  Advanced Audio Coding.  A flexible streaming format that supports multichannel
audio including subwoofer and embedded data channels, using a variety of sample rates up
to 96kHz.  AAC is being developed as a successor to MPEG-2.

Aachen Head:  A binaural microphone developed by Head Acoustics.

AB recording:  In the US, this means recording with a spaced pair.  In Europe, this means re-
cording with a coincident pair.

A/B:  A comparison between two recordings of the same material; pre- and post-equalization,
or pre- and post-effects, or any other comparison between two similar audio devices.

AB-reel:  Term for a 23-minute or 2,050’ maximum reel of film specially made for theater
screening.  The AB-reel may originally have been made from two 1,000’ edit reels;
“Projection reel 1AB” would have been originally been reel #1 and reel #2 during editing and
mixing.  [In the event that the total footage of the first three editing/mixing reels added up to
less than 2,050’, there may be a projection reel “1ABC,” but this is rare.]  It is becoming more
commonplace to edit films in AB reel format as the mag film units are gradually replaced with
DAWs.  AB-reels are also known as “big reels” or “2,000-foot reels.”

AB-reels are not the same as A/B-rolls, in which the camera negative is checkerboarded into
two strands, allowing for simple optical effects such as fades and dissolves to be made when
making original-negative prints (see EK Neg) called interpositives.  This latter process is not
limited to two (A,B) rolls, but can involve as many rolls of film as desired, e.g., a camera
negative cut in four strands would have a “D-roll.”

ABS:  ABSolute time.  Timecode which is the actual running/recording time in HH:MM:SS,

where 00:00:00 is the head of the tape.  For example, DATs use ABS timecode.  See also
feet/frames.

A

absorption coefficient:  The ability of a material to absorb, rather than reflect, sound waves.
A higher absorption coefficient means better acoustical damping.  See bass trap, boundary effect,
standing wave, Sabins.

Material

Frequency (Hz)*

125

250

500

1,000

2,000

4,000

Acoustic Panels

0.15

0.3

0.75

0.85

0.75

0.4

Brick

0.024

0.024

0.03

0.04

0.05

0.07

Carpet

0.05

0.1

0.2

0.25

0.3

0.35

Concrete

0.01

0.01

0.02

0.02

0.02

0.03

Curtains

0.05

0.12

0.15

0.27

0.37

0.5

4” Fiberglass

0.38

0.89

0.96

0.98

0.81

0.87

Wood Floor (joists)

0.15

0.2

0.1

0.1

0.1

0.05

Glass

0.03

0.03

0.03

0.03

0.02

0.02

Seated Person

0.18

0.4

0.46

0.46

0.5

0.46

Plasterboard

0.3

0.3

0.1

0.1

0.04

0.02

Plywood on 2” Batten

0.35

0.25

0.2

0.15

0.05

0.05

3/4” Wood Panel

0.1

0.11

0.1

0.08

0.08

0.11

*Note:  A coefficient of 1.0 means 100% absorption, such as an open window, while 0.0 means 100% reflection.
All figures are given for one square meter of material.

AC-1:  A form of ADPCM first used in 1985 for digital radio (sound-only) applications and
since adopted for other DBS (direct broadcast satellite) services, including soundtrack-with-
video, satellite communication networks, and digital cable ratio systems.  AC-1 has a data
rate between 220 kbps and 325 kbps.

AC-2:  A transform  encoding/ decoding scheme for audio compression developed by Dolby labs
which uses 256-band transform coding at a data rate of 128 kbps or 192 kbps on two chan-
nels.  Used in the Dolby Fax System and also DP5xx encoding.

AC-3:  See Dolby Digital.

ACA:  Active Combining Amplifier.  See combining amplifier.

Academy centerline:  See optical track.

Academy curve/Academy sound:  The name of the standard mono optical track that has been
around since the beginning of sound on film.  Standards were codified in 1938, although the
standard has changed somewhat through the years.  The standard specifies a flat response
throughout the range of 100Hz–1.6 kHz and is down 7dB at 40 Hz, 10dB at 5 kHz, and 18 dB
at 8 kHz.  Also called an N-Curve.  See also X-Curve.

Academy leader:  The visual countdown that precedes the first program frame of a motion
picture.  Symbols and numbers on the academy leader are used for aligning the various film
reels and the optical track for composite printing, for aligning the workprint and edited
soundtracks for mixing, and for timing the change-over from one reel of film to another dur-
ing projection.   Academy leader contains one number per foot following the Picture Start,
with 11, 10, etc., leader to three.  (As projected, these numbers appear upside-down.)  Named
after the Academy of Motion Picture Arts and Sciences, which sets all film format standards.
See also leader, SMPTE Universal leader, plastic leader, fill leader, LFOP.

A

academy Theater:  Specifically, the Samuel Goldwyn Theater at the Academy of Motion
Pictures Arts and Sciences on Wilshire Boulevard in Los Angeles, considered the best-
sounding theater in the world.  Academy members screen films at the Academy Theater
prior to voting on them for the Oscar awards.

AC bias:  See bias.

accelerando:  An indication that the tempo of a piece of music should gradually be increased.

acceptance angle:  The usable working area in front of a microphone is defined by the polar
pattern and is called the acceptance angle.

accidental:  In a musical scale, the accidentals are the extra sharp and flat notes that are not

part of the diatonic series.  For example, in the key of C on the piano, the accidentals are the
black keys.

AC coupling:  Coupling between electronic circuits that passes only time-varying signals
(i.e., alternating current), not direct current.

A-chain:  The part of the motion picture reproduction system in a theater that contains the

sound transducer (such as an optical analog track reader or digital sound format decoder),
preamp, noise reduction and matrix decoding, where applicable.  The A-chain equipment
decodes the sound in preparation for the B–chain and loudspeakers.

AC-M:  A newly developed codec  based on a soft data compression ratio of between 2:1 and
3:1.  Used in the Dolby Digital Dubber, it is designed specifically to record eight tracks of 20-
bit material on removable media, including Iomega Jaz and MO drives.  AC-M is said to be
optimized for multiple record/replay generations.  Initial tests have reported as many as 14
codec processes being possible with no audio degradation.

Acmade:   The British manufacturer of edgecoding machines.

acoustic baffle:  See baffle.

acoustic feedback:  A squealing sound when the output of an audio circuit is fed back in

phase into the circuit’s input.  See feedback.

acoustic intensity:  See sound pressure level.