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Glossary of PA Terms - W |
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The glossary pages provide definitions for over 1900 PA-related terms. If you can't find the term you are looking for, or would like any of the existing definitions to be expanded, please email me − likewise of course if you find any errors in the links etc. Use of this information is conditional upon acceptance of the Disclaimer on the PAforMusic home page.
W * Walla * Warm * Wash light * Watt * Waveform * Wavelength * Wedge * Weighted noise measurement * Weighting filter * Wet * Wet hire * Whistle * White noise * Wi-Fi * Wide * Wide-band * Width * Wind * Winding * Windshield * Wiper * Wire * Wire gauge * Wired microphone * Wireless * Wireless microphone * Wireless system * Wireman * WMA * Woodwind * Woofer * Word * Word clock * Word length * Workers * Working lights * WXGA
The definitions for these terms are given on the assumption of their use in the context of PA systems; many of the terms have more general meanings when used in a wider context. Where more than one definition is given for a term, the definitions are numbered (1), (2) etc.
Some of the definitions themselves use terms (such as "signal") in a specific way − most of these are links (just the first time they are used, in each definition), so just click on them to see the meanings that are intended.
Note that due to font conversions, on some web pages the Greek capital letter Omega, the symbol for ohm, may be displayed by your browser as a 'W'; it should look like a horseshoe shape with a flat base, which, if your browser displays it correctly, now follows: Ω.
Walla
A term used in the film industry to refer to the background
sound made by a crowd of people.
Warm
Describes a sound lacking in harshness.
See also Clarity and
Muddy.
Wash light
A lantern that gives
an even illumination of a relatively large area of the
stage. See also Fresnel.
Watt
The unit of power,
named after James Watt. One watt represents a
transfer of energy at the rate of one joule per second.
For more information on power and power
ratings, see
Power.
See also VA.
Waveform
The 'shape' that would be made by a
signal if its
voltage (usually)
were plotted against time, for example if the
signal were displayed on an
oscilloscope.
The term often refers to a signal having a repetitive
shape (such as a
sine wave),
in which case the waveform has a specific
frequency,
period and
wavelength, and
its waveform may be identified from a single
cycle.
See also Square wave
and Crest factor.
Wavelength
The distance occupied by one
cycle of a
repetitive-waveform wave,
as it travels though some medium (such as air).
The wavelength of sound
waves in air can be of great importance when considering
cancellation effects and other phenomenon such as
refraction,
reflection and
diffraction.
The wavelength can be calculated by dividing the velocity
(speed) of the wave in the relevant medium by its
frequency. This means
that the wavelength of electrical
audio-frequency
signals is very large and
not usually of any relevance, but the wavelength of
electrical
radio-frequency
signals can be significant, especially in relation to
antennae.
For information on the calculation of sound
wavelengths in air, see
Speed of sound.
See also Comb filter.
A slang term for a floor monitor (because these are usually wedge-shaped). See also Slant. Weighted noise measurement
A measurement of noise level in which the noise signal is passed through a weighting filter before the measurement is made. The reason for doing this is usually to take account of the differing sensitivity of the human ear to different frequencies of sound, so that the value of the measurement corresponds more accurately to the level of noise that would be perceived by a person listening to it. The filter is usually an A-weighted type, but CCIR weighting is sometimes encountered − for further details see Weighting. See also Microphone Noise Levels on the Microphones page. Weighting
The process of attributing a different significance, or 'weight', to the different frequencies present within a complex sound or audio signal. The purpose of this is usually to simulate the natural weighting given by the human ear to different frequencies, so that a measurement of the sound or signal level may be made which correlates more accurately with its loudness, as it would be perceived by a person with healthy hearing.
However, the situation is complicated by the fact that the weighting naturally applied by the human ear varies according to the loudness of the sound. At low levels of loudness, the ear has a rather poor response to bass frequencies, improving quite rapidly until an optimum response is reached at around 2.5 kHz; as the frequency continues to rise the response then slowly falls off again. At high loudness levels however, there is a much better response to bass frequencies, and the response is fairly flat from around 200 Hz to 6.5 kHz.
Therefore the weighting applied to the sound or signal to be measured needs to take account of the loudness at which the sound will be heard. For this reason, three different types of weighting have been specified, corresponding to the three standard loudness values of 40, 70 and 100 phons. These weightings are derived from the 'equal loudness' measurement work on human hearing undertaken by Fletcher and Munson, and are defined by specification IEC 651 (or DIN 45412). They are as follows:
- A-weighting, corresponding to the response of the human ear at 40 phons. This is the most common type, and is most frequently encountered in the measurement of noise (because noise in PA systems is usually at a low level of loudness). To achieve this response a bandpass filter centered on a frequency of 2.5 kHz is used; its attenuation increases steadily as the frequency falls below 2.5 kHz (20 dB attenuation at 100 Hz), and increases much less rapidly as the frequency rises above 2.5 kHz (10 dB attenuation at 20 kHz).
- B-weighting, corresponding to the response of the human ear at 70 phons. This type is the least commonly encountered. It has a similar high-frequency response to A-weighting, but has a rather less severe attenuation of low frequencies.
- C-weighting, corresponding to the response of the human ear at 100 phons. This type is suited to sound pressure level measurement in loud environments such as rock concerts, dance clubs and noisy industrial environments. This has a similar high-frequency response to A-weighting, but has a far less severe attenuation of low frequencies.
Another type of weighting, generally used only in noise measurement (especially of microphones), is 'CCIR weighting', specified by CCIR 468 (or DIN 45405). For further information on microphone noise levels, see Microphone Noise Levels on the Microphones page.
Note that, when a weighting is used in the measurement of a signal (or noise) level, there is an implicit assumption that, overall, no modification of the frequency response (or other modification such as distortion) occurs in the system between the point of measurement and the acoustic sound waves that are eventually heard.
Note also that the term 'weighting' is occasionally used to refer to the response given by equalising filters such as those used in the recording and playback of analogue recordings − see RIAA and Tape equalisation − though to avoid confusion this usage of the term is best avoided.
Weighting filterA filter specifically designed to give more emphasis (or 'weight') to certain frequencies present within a signal, usually in order to simulate some natural filtering effect such as the response of the human ear. Such filters are most often used in the measurement of sound pressure levels and in the measurement of noise levels. Different types of filter will give different weight to each frequency, and so will give a different result to the measurement. For more detailed information see Weighting.
Wet
Describes a sound laden with
effects.
Compare Dry.
Wet hire
Hiring of equipment (usually a complete system) from a
hire company, that includes the personnel to assemble and
operate it, as compared to hire (usually of individual items)
on a 'self assemble and operate' basis.
Compare Dry hire.
Whistle
Feedback at a high audio
frequency.
White noise
A particular type of noise,
whose level
remains constant over the entire audible
frequency
range. More accurately, frequency bands of equal
bandwidth contain the
same amount of noise power.
See also Pink noise
and IEC noise.
Wi-Fi
See IEEE 802.11.
Wide
Describes an effect which has
a strong stereo component.
See also Width.
Wide-band
Describes a signal
(often noise) or
equipment (often a filter)
having a relatively large
bandwidth.
Compare Narrow-band.
Width
A term used to describe the extent to which sounds
within a mix deviate
from a central position in the
stereo image.
However, the actual 'width' experienced by a listener
will depend on a number of factors, particularly upon
their distance from the
speakers
as compared to the distance between the Left and Right
speakers. See also Pan,
Mid-side pair
and Wide.
Wind (musical instruments)
See Woodwind and
Brass.
Winding
See Transformer.
Windshield
A device, usually made of acoustic foam, that is placed
over the sound aperture of a
microphone to reduce the
unwanted popping noises that
result from plosives
(and, in outdoor events, to reduce wind noises) without
significantly affecting the quality of the
wanted sound. Also known as a 'sock' or a 'pop filter'.
See also Basket.
Wiper
The moving electrical contact of a
potentiometer.
It contacts with the track
of the potentiometer.
Wire
A flexible single
conductor whose length
is very much greater than its diameter, usually having
an easily-removed
insulating covering
or coating. It is used to provide a path for an electric
current internal
to equipment or within a
cable, and may be stranded or
solid-cored.
Non-technical personnel frequently use this term to
refer to a cable, but this usage is deprecated by
engineers.
The amount of current that can be safely carried by a
wire is determined by its gauge
and by other factors such as the type of
insulation it has and the ambient temperature when
in use.
Wire gauge
See Gauge.
Wired
microphone
A microphone that is
connected to the PA system
by means of an attached cable,
rather than via a
wireless link. Compare
Radio
microphone.
Wireless
Describes equipment that is is able to send or
receive a signal
by a means other than through a
cable, most commonly by
use of radio-frequency
transmission or reception.
Wireless
microphone
See Radio
microphone.
Wireless
system
A separate transmitter and receiver unit that communicate
with each other wirelessly.
Most commonly refers to a
radio
microphone system, in which case the
microphone itself
may or may not be included as part of the system.
Wireman
A person whose job is to install
cables and make the
required connections to them.
WMA
An abbreviation for 'Windows Media Audio', a
digital audio file
format suitable for playing on PCs, personal audio
players, etc..
Woodwind
Describes a particular class (or 'section')
of orchestral musical instruments, including the flute,
piccolo, clarinet and oboe. (Note that these instruments
are not necessarily made of wood.)
Woofer
A driver which is designed
specifically to handle bass
frequencies. It is used
in a bass bin and as the
low frequency driver in
full-range
speakers. Pronounced
"wuffer". See the
Amps and Speakers page for
further information.
Word
The smallest meaningful unit of
digital information in a
particular system, for example, one sample of a
single channel of an
audio
signal.
It consists of several bits,
often comprising one or more complete
bytes.
Word clock
A clock
signal which
indicates the rate at which
words
are conveyed or processed in a
digital system.
So, its frequency
is the same as the sampling rate.
See also Bit clock and
Analogue
to digital conversion.
Word length
The number of bits in
a word.
Workers
A slang term for
'working lights'.
Working lights
Lights which are not used during a performance, but only
to provide light for the crew
during the rigging
and de-rigging of the system.
In a purpose-built performance venue they may be permanent
fixtures; otherwise they are mobile equipment and are usually
the first items to be rigged and the last to be de-rigged.
WXGA
An abbreviation for 'wide extended graphics adaptor'.
A standard interface
for the connection of display
equipment (such as monitors and projectors) to
computers. The standard gives a resolution of
1280 pixels horizontally
and 800 pixels vertically. Note that this format gives
a less-common
aspect ratio of 8:5
(most usually employed for the integrated
LCD displays of laptop
computers).
See also VGA,
SVGA,
XGA,
SXGA,
UXGA and
DVI.
The most commonly encountered standards, their resolutions
and aspect ratios are tabled under the entry for
VGA.
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This page last updated 27-Feb-2010.