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
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
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
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
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