A
Absorption: The tendency of
sound waves to be soaked up by soft surfaces.
Acoustic
Feedback: is caused by a regeneration of sound leaving a speaker
and entering a microphone. This tone - a sustained shriek - is a
self-perpetuating cycle that can be stopped by decreasing the volume.
Sometimes referred to as a standing wave.
Acoustics:
1. The science or scientific study of sound.
2. The properties of a room or environment that affect
the qualities of sound.
Acoustic Power Output: The
output, as measured in watts, of anything that generates sound.
Acoustic Suspension: A
type of speaker cabinet which is sealed to control the action of its woofer and
prevent the leakage of air.
Ambient Noise Level: Background
noise from any source that affects the listener's ability to hear what is
produced by a sound system. For example Working Machinery noise, humming from
florescent lights, honking traffic, etc.
Amplifier (Amp):
1. An electronic device that increases the amplitude
of a signal.
2. A combination speaker/amplifier designed for use
with an instrument, as with a guitar or keyboard (preamp,
power
amplifier)
Amplitude:
1. The strength of sound waves or an electrical
signal, as measured against a mean. 2. That which determines loudness.
Anechoic:
1. The complete absence of reflected sound (echo).
2. An environment that prevents (through dissipation
and absorption of sound waves) all reflected sound, as in an anechoic chamber.
Attenuate: To make weaker. An attenuator uses
resistance to reduce output voltage, as with a volume control.
B
Balanced Line: A
pair of ungrounded conductors whose voltages are opposite in polarity but equal
in magnitude. Balanced lines reduce interference from external sources like
radio frequencies and light dimmers since they are typically shielded by a
third conductor surrounding them.
Basket: The frame to which a driver's cone is mounted.
Bass: The lower end of the frequency range, from
about 20 Hz to about 300 Hz.
Bass Reflex: A speaker that,
as a means of enhancing the efficiency of the reproduction of bass frequencies,
channels some of the sound pressure generated by its woofer(s) through an
opening (port) in its cabinet.
Bi-amplification: The use of
separate amplifiers to power woofers and tweeters.
C
CPS (Cycles Per
Second): The number of plus/minus voltage swings or
compressions/rarefactions of air molecules occurring each second in an
electrical or audio signal; usually expressed as hertz (Hz).
Cardioids: "Heart" shaped pattern exhibited by
some microphones which reduce pick-up from the sides and back.
Clipping: Audible
distortion that occurs when a signal's level exceeds the limits of a particular
circuit. When an amp is "turned up too loud," and begins to distort,
it is said to be clipping. On an oscilloscope clipping appears to flatten the
tops and/or bottoms of the waveforms as if someone took scissors and
"clipped or cut" the top and bottom of the wave.
Compression Driver: A transducer, designed for use with a horn, which
utilizes a diaphragm (rather than a cone) to reproduce mid and high
frequencies.
Compressor: A
device that reduces - compresses - a signal's dynamic range.
Condenser Microphone: A
MIC that depends on an external power supply or battery to electrostatically
charge its condenser plates.
Conductor: A
substance - in electronics, usually a metal - that allows the free flow of
electrons.
Cone: The
vibrating diaphragm, employed in some speakers designs, that generates sound
waves.
Console: A
large or elaborate mixer required to massage the ego of the band's sound man.
Critical Distance: The
distance from a sound source at which sound pressure levels emitted by the
source equal those being reflected off of other surfaces.
Crossover
(Crossover Network)- Electronic: An electronic device or circuit that, when
inserted between a mixer and amplifier, divides the audio spectrum into
individual frequency ranges (low, high, and/or mid) before sending them to
specialized amplifier/speaker combinations. An advantage of this type of
crossover is that it increases efficiency.
Crossover (Crossover
Network) - Passive: An electronic device that, when inserted after
the amplifier, divides the audio spectrum into individual frequency ranges
(low, high, and/or medium) before sending them to specialized speakers (see:
tweeter, woofer, and mid-range).
Current: The
movement - or flow- of electrons.
D
dB (Decibel):
1. A relative unit of measure between two sound or
audio signal levels. A difference 1 dB is considered to be the smallest that
can be detected by the human ear. An increase of 6 dB equals twice the sound pressure.
2. As a measure of sound pressure levels, used to
indicate loudness.
Delay:
1. The postponement of an audio signal for a specific
amount of time, usually measured in milliseconds.
2. A device designed to delay an audio signal.
Diaphragm:
1. The radiating surface of a compression driver; its
vibrations emit sound waves.
2. The moving element of a microphone.
Dimmer Noise (hash): The
noise that originates in the switches used to dim lights and can be heard in a
sound system.
Directivity: The
ability of a speaker or horn to direct sound to a given area which can be
described by its directivity factor (Q).
Dispersion: The
area throughout which the sound produced by a speaker is distributed.
Distortion: Any
discrepancy between the source material and the sonic output of a sound system.
Ducking: The
use of an electronic device to automatically reduce the volume of music or
other backgrounds fill when an announcer begins speaking.
Dynamic
Microphone: A microphone that converts sound into electrical
pulses by means of a moving electromagnetic coil.
Dynamic Range: The
difference between the softest and loudest extremes within an audio signal.
Dynamics Processing: The
use of electronic devices to control the levels of audio signals and compress
or expand their dynamic range.
E
Effects Loop: inputs and
outputs that allow the sending of an audio signal to and from a signal
processor such as a reverb unit, delay, gate or limiter.
Efficiency: The ratio of a
device's energy output to its energy intake.
Electret Microphone: A
condenser microphone which, instead of employing an external high voltage power
source, relies on permanently polarized plates, a low voltage power supply, and
internal preamp.
Equalization (EQ): The
electronic manipulation of specific frequencies.
Equalizer (EQ): A
device that permits the precise control of specific frequency ranges. Examples
are: Graphic, Parametric, Notch Filter, Cut only.
Expander: an
electronic device that increases dynamic range by reducing a signal's level any
time it falls below a specific threshold.
F
Fader: The signal output control found on the channel,
sub-master, and master sections of a mixer.
Ferro Fluid: An
emulsion containing metal particles, used to conduct heat away from a speaker's
voice coil.
Filter: A
device that removes unwanted frequencies or noise from a signal.
Flat: The state of an audio signal or tone whose
frequency is unaltered by equalization. On most mixers and equalizers flat is
indicated by the tone controls being at dead center.
Fletcher Munson Curve: A
graphic representation of average hearing responses of carbon-based units at
particular sound pressure levels.
Foldback: an
output, that by splitting an input signal (independently of the mixer
controls), allows that signal to be sent a separate device. Foldback makes it
possible for a performer to create his/her own monitor mix without affecting
the front of house mix.
Frequency:
1. The number of sound waves that pass a given point
in one second.
2. The determiner of pitch. (Ask Kenneth).
Frequency Response: The
range of frequencies that are reproducible by a speaker or electronic
component.
Front of House (FOH): the
components of a PA that are directed toward the audience, as opposed to the
back of the house or monitor system.
G
Gain:
1. The amplification characteristic of an electrical
or mechanical device.
2. The amount of volume that may be achieved before
acoustical feedback occurs.
Gate: An
electronic device that increases dynamic range by cutting off a signal when its
level falls below a specific threshold. Used to control leakage of sound source
into adjacent MICs (ie drums).
H
Hz (Hertz): A
unit of measure that equals one cycle per second.
High Pass Filter: A
circuit that discriminates between high and low frequencies and allows only the
high frequencies to pass.
Horn: An
acoustical transformer which, when coupled to a driver, provides directivity
and increases the driver's loudness.
Hypercardioid: A
narrower heart-shaped pick-up pattern than that of cardioid microphones.
I
Impedance: The measure of total resistance to the current
flow in an alternating current circuit; expressed in ohms, as a characteristic
of electrical devices (particularly speakers and microphones). Most speakers
are rated at 8 ohms. Microphones are usually classified as being either high
impedance (10,000 ohms or greater) or low impedance (50 to 250 ohms).
Inductance: A circuit's
opposition to a change in current flow.
Input Overload Distortion: Distortion
caused by too great an input signal being directed to an amplifier or
preamplifier. Input overload distortion is not affected by volume control
settings and most frequently occurs when mics are positioned too close to the
sound source. Input overload distortion is controllable through the use of an
attenuator.
Inverse Square Law: The
law that states that in the absence of reflective surfaces, sound pressure 9or
light) falls off at a rate inverse to the square of the distance from its
source. In other words, every time you double your distance from the sound
source, the sound pressure level is reduced by 6 dB.
J
Jack: A female input or output connector, usually for a MIC
or an instrument
L
Limiter: A
device that electronically controls or "limits" the peak levels of
program material.
Line Level: A
signal whose voltage is between approximately 0.310 volts and 10 volts across a
load of 600 ohms or greater.
Load: Any device to which power is delivered.
Low Pass Filter: A circuit that
discriminates between high and low frequencies and allows only the low
frequencies to pass.
M
Microphone Processor: A
device that, when installed between a MIC and an amp or preamp, allows the
manipulation of the signal originating at the MIC.
Mixer: An electronic device that permits the combining
of a number of inputs into one or more outputs. Mixers commonly provide a
variety of controls - tone, volume, balance, and effects - for each
"channel."
Monitor: A
speaker or earphone dedicated to making it possible for a performer to hear -
or monitor - his/her own performance. Examples are: floor wedges, side fills, or
mini-monitor.
Motor: The magnet structure of a speaker
N
Noise Gate: A device that
attenuates a signal when the program level falls below a preset threshold.
O
Ohm: The
basic unit of measurement of resistance.
OHM'S Law: The
law that states the relationship between current, resistance and voltage in an
electrical circuit: Amperage times resistance equals applied voltage.
Omnidirectional: Capable
of picking-up sound or radiating sound equally from all directions; as with a unidirectional
microphone or subwoofer.
Oscilloscope: An
electronic device that displays, on a video screen, a representation of an
electrical signal.
P
PA: Abbreviation of public address system:
one or more speakers connected to an amplifier; may include a mixer and any
combination of sound reinforcement devices.
Pad: An attenuator-An attenuator is an
electronic device that reduces the power of a signal without appreciably
distorting its waveform. An attenuator is
effectively the opposite of an amplifier, though the two work by different
methods. While an amplifier provides gain, an attenuator provides
loss, or gain less than 1
Patch Cord: A short
electrical cable used to connect individual components of a sound system
Personal Monitor: A
monitor that is small enough to be directed at a specific performer. Before
these devices, monitors were usually arrayed along the front of the stage and
shared by the entire ensemble.
Piezo Tweeter: A
driver which is dedicated to the reproduction of high frequencies and operated
by means of a crystal rather than an electromagnet.
Phantom Power: Operating voltage
supplied to a condenser mic by a mixer or external power source.
Phase: The relationship of an audio signal or sound
wave to a specific time reference.
Phase shift: The
phase relationship of two signals at a given time, or the phase change of a
signal over an interval of time.
Pin 2 Hot: Considered
the standard polarity for pro audio.
Pitch Tone: A function of frequency.
Polarity: A
condition which has two states (in or out) and is usually described in one of
three ways:
1. Acoustical to electrical (microphone): Positive
pressure at diaphragm produces positive voltage at pin 2 of XLR or at the tip
of a ¼-inch phone plug.
2. Electrical to acoustic: Positive voltage into the
"plus" terminal of a speaker causes the speaker's diaphragm to move
forward (produces positive pressure).
3. Electrical to electrical: Positive voltage into pin
2 of an XLR plug or at the tip of a ¼-inch phone plug produces positive voltage
at the output (pin 2 of XLR jack, the tip of a ¼-inch phone plug, or the red
(plus) connector of a binding post (banana terminal)).
Potentiometer (Pot): A
variable resistor (rotary or linear) used to control volume, tone, or other
functions of an electronic device.
Power Amplifier: An
electronic device that increases the volume of a signal. A basic unit of all
sound systems. Power amps are typically connected to a preamp which provides
controls for individual functions: level, tone, etc.
Proximity Effect: An
increase in the bass response of some mics as the distance between the MIC and
its sound source is decreased
Q
Q: A ratio obtained by complex mathematical
calculations involving the relationship of a speaker's direct radiated energy
to its total radiated energy (directivity index). When measured on-axis, Q
(which is dependent on frequency) is used to determine a speaker's suitability
for a particular application.
R
Radio Frequency Interference (RFI): Radio
signals from external sources that invade and can be heard through, sound
systems.
Reflection: A
term that describes the amount of sound "bouncing" off of hard
surfaces.
Rejection: A
microphone's ability to selectively exclude sounds coming from outside it's
pickup pattern.
Resistance: Opposition
measured in ohms to the flow of electrical current.
Reverberation: sound
waves that continue to bounce around a space after the sound source has ended.
Room: Any enclosed space in which a performance is staged.
It can be as small as a closet or as large as the Superdome.
S
SPL (Sound Pressure Level): A
measurement of the volume of sound, expressed in decibels (dB): a function of
amplitude.
Sensitivity: The
sound pressure level directly in front of the speaker (on-axis) at a given
distance and produced by a given amount of power.
Shield: A metal enclosure that prevents electronic
components from being affected by unwanted interference. Shielded speakers may
be placed near a TV, for instance, because their magnets cannot affect the
picture tube.
Shelving: The
setting of the on-axis output of complementary drivers (woofers, mid-range,
tweeters) to provide the desired frequency response.
Sibilance: A
hissing sound produced when pronouncing S and Z. Sibilance is undesirable in
professional sound reinforcement and can be controlled through the use of a
"de-esser" like Valley Audio's 401 Microphone Processor, 815 Dynamic
Sibilance Processor, or 730 DynaMap Digital Dynamics Processor.
Signal: An electrical impulse. First popularized by Paul
Revere.
Signal-To-Noise-Ratio: The
ratio, expressed in dB, of an electronic device's nominal output to its noise
floor.
Snake: A cable - often running between the stage and control
board - that combines multiple lines; used to connect MICs, instruments and
monitors to a mixer.
Sound Level Meter: A
device that measures, in dB, the amplitude of sound waves.
Sound Pressure Level (SPL): The
measurement of loudness, or amplitude, of sound, expressed in dB.
Sound Reinforcement: The
use of electronic devices to reinforce, alter or increase the level of sound.
Spider: An internal speaker component whose function is to
precisely position the voice coil in relation to a gap in the motor.
T
Toe-in: The degree to which the inside front edges of a
pair of speakers are angled toward each other.
Transducer: A device which
converts sound into electrical energy (a microphone), or electrical energy into
sound (a speaker).
Transformer: A device that alters
electrical current.
Tweeter:
A speaker (driver) that reproduces only frequencies above a certain range,
usually about 3 kHz.
U
Unbalanced Line: Cable
that consists of one conductor and a shield. Here the shield is also carrying
the other half of the signal.
Unidirectional: A MIC that
picks up sound primarily from one direction.
V
VCA (Voltage Controlled Amplifier):
An amplifier whose output is controlled by varying its voltage rather than by
direct resistance (as with a potentiometer).
Voice Coil: Wire, usually
copper, wrapped around a former (tubular core). When attached to a cone or
diaphragm, surrounded by a magnetic field, and set into vibration by an
alternating current, a voice coil causes a speaker to emit sound waves.
Voltage: The electrical pressure (electromotive force) of a
current within a circuit.
W
Watt:
1.
A unit of measurement that equals about 1/746 horsepower or enough electrical
energy to perform 1 joule per second. A joule describes the energy of 1 Newton
displace 1 meter in the direction of the applied force. A Newton is the amount
needed to accelerate 1 kilogram of 1 meter per second.
2.
One volt multiplied by one amp.
Wedge: A monitor speaker, in the shape of a wedge,
designed to sit on the floor and be directed toward the performer(s).
Woofer: A speaker (driver) that reproduces only frequencies
below a certain range, usually about 800 Hz.
X
XLR: Connector
A three-pin connector widely used in the audio industry.