A measure of the acoustic absorptive characteristics of a material
named after Professor W.C. Sabine. Open air is said to be 1
Sabin. Other materials have a coefficients beween 0 (totally
reflective) and 1 (totally absorbtive). Charts listing these
numbers are available and give the absorbtion coefficients at
A feed, an output signal. Usually line level. On mixer, usually
refers to either an effects or auxiliary output designed to
go to an outboard device and return the processed signal to
1. The ability of a microphone to pickup very quiet sounds
results in a higher sensitivity number.
2. The ability for a speaker to produce a louder sound when
fed the same amount of power as another speaker. The SPL output
for a given input level (usually tested with 1 watt of input
power with a test instrument 1 meter directly in front of the
3. The ability of a wireless microphone receiver to pickup very
weak RF signal levels.
sensorineural hearing loss
SDL (servo-drive loudspeaker)
A sound that's not flat. Either the frequency response of a
device as in shaped microphone for vocal response, or a signal
that has been adjusted for equalization.
A type of equalization where the frequencies either above or
below a given point are raised or lowered equally. Shown on
a graph, it would be flat up to the frequency point, then it
would go up or down to a given level and then flatten out again.
Typically the high and low frequency equalizer controls are
shelving type controls.
1. A wiring or covering over either a wire or circuit which
blocks RFI from entering the wiring and thereby causing noise.
In microphone wiring, it may be a foil type wrapping or a braided
wire. Foil gives a 100% shield while a braided shield is less
than 90%. The shiled of a wire is connected to a drain wire
(in the case of a foil shield) which is then connected to pin
1 of an XLR type connector.
2. Faithas in spiritual armour.
A device that holds something else stable even if it's bumped
or shaken. In microphones, the shock mount goes on a microphone
stand so if the stand is bumped, the microphone doesn't pick
up the vibrations (noise).
1. Term for short circuit. A circuit where two (or more) wires
are (usually) connected unintentionally. It often results in
no sound or damaging equipement or a component.
2. The opposite of tall. "The stool was so short I couldn't
see the stage over the sound board."
A type of supercardioid microphone which looks like a long
(up to 3') tube with slits in it. Very directional.
Hissing sound. The "S" sound in "this",
Refers to an electrical current present on a wire or in a circuit
which represents a soundwave. The electrical representation
of the sound going down the wires from one piece of equipment
A category of electronic devices which cause some type of change
to an audio signal. This includes (but is not limited to) equalizers,
delay units, effects units, limiters, and crossovers.
signal to noise ratio (S/N)
The ratio between the nominal level of a signal (0 dBm) and
the general circuit noise level (noise floor) measured in dB.
All electronic devices produce noise. The S/N ratio is a measure
of how quet the device is by indicating how low the level is
of the inherant noise.
A single, strong echo heard off a surface.
see flutter echo
The largest contact of a 1/4" (or mini) phone type connector.
The cable shield or common wire is connected to this point in
balanced wiring, the negative and shield in unbalanced wiring
is connected here. Same as the shell of the connector.
A variable resistor that moves in a straight linear fashion
as opposed to a rotory control. Typically used on mixers to
adjust the channel voume level.
1. A long multi-pair cable usually with a box at one end (the
head) with multiple input and some output jacks and connectors
at the other end to allow a microphone to be plugged into the
head, then the corresponding connector plugged into a mixer
at the other. A multi channel extension cord for microphones.
2. An animal without legs. AKA serpent as in the animal that
deceived Eve in the Garden of Eden.
3. A person who acts deceptively and sell you inferior audio
equipment at outrageous prices.
Another term for AFL. Listening to one (solo) channel of a
mixer after EQ, after inserts, after panning, after all processing.
sound pressure level
The power level of sound being the sound pressure squared,
referenced to 20 mPa2 measured in dB. Commonly, how loud the
sound is measured in decibels. Speech is around 70-80 dB at
three feet. Normal background noise on average is 50-60dB. 120dB
is the threshold of pain. 200dB is 50lbs of TNT detonated 10
The act or application of audio processing equipment to reinforce
and amplify sound instantaneously. Adding the processed sound
to that of natural sound from the sound source so that all can
hear. One of the three major applications of audio equipment
as opposed to recording or broadcast. Sound reinforcement takes
a weak sound and makes it loud enough for people to hear.
An oscilation of air pressure. One wave is measured from the
point of null (average room) pressure past both points of greatest
(crest) and least (trough) pressure to the point of normal pressure.
The length of the wave is measured in feet. The frequency is
measured in Hertz (when time is factored in).
A type of connector used for speaker connections developed
by the company Neutrik. Has four or eight contacts (depending
on the model). The plug locks into the jack so it can't be pulled
out. Becoming accepted as the standard professional speaker
connector due to its electrical handling and mechanical features.
How well you can understand what is being said. Though you
may "hear" the sound, you may not understand it (and
it's useless). Measurements can be taken to quantify what the
intelligibility of a room and/or sound system are.
speed of sound
The speed at which sound waves travel through a medium (usually
air). Since the speed of waves is affected by the density of
the medium and the density is affected by the temperature and
pressure, the speed of sound through aid varies depending on
these (and other) factors. A true measurement must state under
what conditions it was measured. The standard reference is 1,130
feet per second at 59-degrees F at sea level (standard barametric
pressure). The speed of sound increases with humidity, too.
1. Short for spill-over. Refers to sound that's heard in an
area it's not intended to be in. The most common example is
stage monitor spill--when the sound from stage monitors is heard
in the audience/congregational seating area.
2. What you must be very, VERY careful not to do when drinking
and running a sound board.
A device which splits something into multiple parts, usually
having multiple outputs the exact same as the original (as opposed
to dividing something). In sound systems, common splitters are
antenna splitters to allow multiple wireless receivers to operate
from the same antenna(s) or an audio signal splitter to send
one signal to multiple destinations.
see distribution amplifier
1. Fanning the walls in a room so they are not parallel.
2. Angling adjacent speaker boxes or drivers away from each
other to achiever the appropriate and desired coverage while
minimizing comb filtering.
A device that creates a reverb effect by passing an electrical
signal through a coil spring. Is the older, cheaper, and more
limited design compared to digital effects units. Has the annoying
habit of causing a loud bang, boing, or slap when the unit is
bumped (usually during the quietest part of the service).
The circuit in a wireless microphone reciever that automatically
mutes (turns off) the audio output when the RF level drops out
or is too weak to be received properly.
The noise caused by feet on the floor (stage) or any other
undesired sounds generated on the stage such as prop movement
or microphone stand movement. Most common in wooden stages (which
tend to magnify the low frequency portions of the sounds).
Any mechanical device that allows a device to be attached to
a stand such as a microphone or speaker stand.
see microphone clip
Derived from a Greek word meaning "solid". The sound
is solid or sounding like it's coming from one side or the other
instead of from the individual speakers themselves. Commonly
though it refers to any two channel audio system especially
as contrasted to mono. Usually the two channels have different
information (signals) on them which means that if you're closer
to one speaker than the other, you'll hear an unbalanced reproduction
which is why most sound reinforcement systems are done in mono.
A panoramic acoustical image derived from two sources. The
effect of being able to identify the location of different sounds
from different places anywhere between sources.
A microphone that has two (or more) elements in it to derive
a stereo image of the source. It has two (different) output
signals as well.
A dual channel line input on a mixer with one set of controls
for both inputs. Usually has limited control capability (EQ,
etc.) It's designed to take the output of an effects device
(where the effect is returned in to the mixer).
A fader on larger mixers that receives the level of all the
input channels that are assigned to it, controls the level of
the combined signal, and then passes that signa on to the master
level controls. Often subgroups have their own independant outputs
to allow for multi-track recording. Features on a subgroup vary
depending on the mixer. The concept is to allow multiple microphones
that are related (like all the drum mics or all the male background
vocals) to have one overall control each.
Term for subgroup. Submasters are usually distinguished from
subroups in that there will only be a left and right (subgroups
usually have 4 to 8 controls).
A mixer that's used to mix several sources together and then
output the signal to another mixer. This allows more inputs
to be mixed than the master mixer can handle (or for the submix
to be done at a location different than where the main mixer
A speaker that's designed to reproduce very low frequencies
(only), typically below 50Hz. Usually employs the use of very
large cone drivers. The frequency range and size of the subwoofers
is relative to the rest of the speaker system they are designed
to accompany. If a main speaker has a frequency response down
to only 80Hz, the subwoofer used may cover 50Hz to 80Hz. If
the main system goes down to 50Hz, the subs may operate from
30Hz to 50Hz.
A mono signal that's derived by mixing the left and right stereo
signals together. The mono signal is then whatever the sum of
the two signals. If the two signals contain information that's
opposite each other, it will cancel (leaving no signal). Any
variation of the two signals will result in some frequencies
partially or totally cancelling while others will be enhanced.
This is in contrast to discrete mono where the signal is always
and only one signal.
A microphone that's more directional than a cardioid microphone.
Typical specifications are: coverage angle=115-degrees, maximum
see also: bidirectional; cardioid; hypercardioid; omnidirectional
A speaker system that has speakers both in front and behind
the listener. Can mean a variety of channel separation and speaker
placement systems. Most commonly, involves left and righ tchannels
placed to either side of the front "screen" each with
different signal information. A center channel wil be placed
in the middle of the front screen but may be either a discrete
or summed mono channel (used primarily for speech). Typically
in a theater, the side and back speakers are all one discrete
channel. In current home theaters, the back speakers are usually
a mix of the left and right channels at lover levels. The subwoofers
are usually a summed mono signal.
An equalizing control or filter that has a variable center
frequency. This allows the user to cut or boost a range of frequencies
centered around a frequency that's determined by a separate
contorl rather than only the range of frequencies pre-determined
by the device.
Vertical and horizontal pulses in a composite video signal
that maintain the horizontal and vertical scanning procedures
of the video picture signal.