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echo
The reflection of sound from a surface such
as a wall or a floor. Reverberation and echo are
terms that can be used interchangeably, but in
audio parlance a distinction is usually made:
echo is considered to be a distinct, recogniz-
able repetition (or series of repetitions) of a
word, note, phrase or sound, whereas rever-
beration is a diffuse, continuously smooth
decay of sound. Echo and reverberation can be
added in sound mixing by sending the original
sound to an electronic (or electronic/acoustic)
system that mimics natural echoes, and then
some. The added echo is returned to the blend
through additional mixer inputs. Highly echoic
rooms are called live; rooms with very little
echo are called dead. A sound source without
added echo is dry; one with reverb or echo
added is wet.
effects devices
External signal processors used to add re-
verb, delay, spatial or psychoacoustic effects to
an audio signal. An effects processor may be
used as an insert processor (serial) on a par-
ticular input or subgroup, or it may be used via
the aux send/return system(parallel). See also
echo, reverb.
EIN
Equivalent Input Noise. Specification that
helps measure the “quietness” of a gain stage by
deriving the equivalent input noise voltage nec-
essary to obtain a given preamp's output noise.
Typically ranges from –125 to –129.5 dBm.
EQ
See equalization.
EQ curve
A graph of the response of an equalizer,
with frequency on the x (horizontal) axis and
amplitude (level) on the y (vertical) axis.
Equalizer types and effects are often named
after the shape of the graphed response curve,
such as peak, dip, shelf, notch, knee and so on.
equalization
Equalization (EQ) refers to purposefully
changing the frequency response of a circuit,
sometimes to correct for previous unequal re-
sponse (hence the term, equalization), and
more often to add or subtract level at certain
frequencies for sound enhancement, to remove
extraneous sounds, or to create completely
new and different sounds.
Bass and treble controls on your stereo are
EQ; so are the units called parametrics and
graphics and notch filters.
A lot of how we refer to equalization has to
do with what a graph of the frequency re-
sponse would look like. A flat response (no
EQ) is a straight line; a peak looks like a hill, a
dip is a valley, a notch is a really skinny valley,
and a shelf looks like a plateau (or a shelf).
The slope is the grade of the hill on the graph.
Graphic equalizers have enough frequency
slider controls to form a graph of the EQ right
on the front panel. Parametric EQs let you vary
several EQ parameters at once. A filter is sim-
ply a form of equalizer that allows certain
frequencies through unmolested while reduc-
ing or eliminating other frequencies.
Aside from the level controls, EQs are prob-
ably the second most powerful controls on any
mixer (no, the power switch doesn’t count!).
fader
Another name for an audio level control.
Today, the term refers to a straight-line slide
control rather than a rotary control.
family of curves
A composite graph showing on one chart
several examples of possible EQ curves for a
given equalizer or equalizer section.
filter
A simple equalizer designed to remove cer-
tain ranges of frequencies. A low-cut filter
(also called a high-pass filter) reduces or
eliminates frequencies below its cutoff fre-
quency. There are also high-cut (low-pass)
filters, bandpass filters, which cut both high
and low frequencies but leave a band of fre-
quencies in the middle untouched, and notch
filters, which remove a narrow band but leave
the high and low frequencies alone.
flanging
A term for phasing. Before digital delay ef-
fects units, phasing could be accomplished by
playing two tape machines in synchronization,
then delaying one slightly by rubbing a finger
on the reel flange. Get it?
FOH
An acronym for Front Of House. See house
and main house speakers.
frequency
The number of times an event repeats itself
in a given period. Sound waves and the electri-
cal signals that represent sound waves in an
audio circuit have repetitive patterns that range
from a frequency of about 20 repetitions per
second to about 20,000 repetitions per second.
Sound is the vibration or combination of vibra-
tions in this range of 20 to 20,000 repetitions per