Specifications

216
GLOSSARY
tion voltage. Instead, a special metalized plas-
tic “electret foil”, in which a permanent electri-
cal charge has been stored by application of
heat and a high polarizing voltage, is used
either for the diaphragm or the fixed electrode.
The latter type is called “back plate electret
microphone”.
Electromagnetic Wave Spectrum
Range of frequencies of electromagnetic radia-
tion.
Environment
Dynamic microphones will generally stand up
to extreme environmental conditions such as
temperatures from -25 °C to +70 °C and high
humidity.
Condenser microphones, however, are suscepti-
ble to humidity and condensation. When an
object is damp and colder than its environ-
ment, condensation water will form on its sur-
face. Drops of condensation water inside the
transducer or high-impedance preamplifier will
cause crackling noises.
Storing condenser microphones:
1. Store the microphone in a dry and warm
place. It should never be colder than its
environment. If it has been transported in a
cold car or van, allow it to warm up before
use.
2. The supplied silica gel absorbs humidity. It
will maintain this property as long as you
keep it in the sealed package and may be
regenerated in the oven if necessary.
3. Be sure to protect condenser microphones
from rain when using them outdoors.
Equivalent Noise Level
Since condenser microphones incorporate a
preamplifier, they introduce a low amount of
self-noise which appears at the microphone
output as an unwanted signal voltage. This
noise voltage is measured using standard
weighting filters and the result stated as the
equivalent noise level in dB. An equivalent
noise level of 20 dB, for instance, means that
the self-noise of the microphone is as loud as a
sound at 20 dB SPL (see dB SPL).
Noise level in quiet recording studio:
A low equivalent noise level means that the
microphone's self-noise is low. The self-noise
voltage is weighted either conforming to IEC
268-1 and DIN 45 405 using the filter accord-
ing to CCIR 468-3 with the “quasi-peak” value
being quoted, or in accordance with IEC 651 or
DIN 45 412 using the A-weighting curve with
the rms value being quoted. Studio engineers
seem to prefer the CCIR weighting while A-
weighting is still accepted as well.
ERP
Equivalent Radiated Power,
a measure of a transmitter's RF output.
Far-Near Difference
The difference between the shortest and the
longest distance between stage and antenna.
Feedback
When a microphone picks up amplified sound
from a loudspeaker this signal will be reampli-
fied, picked up again, etc., until the commonly
known shrill howling (sometimes a lower
midrange rumbling) sets in.
In small rooms, feedback is usually caused by
reflections. In this case, acoustic treatment of
the walls should help. On stages with correctly
set up FOH speakers it is the monitor speakers
that may cause feedback. A very good hyper-
cardioid microphone (e.g. a D 3900) may some-
times provide a few extra dB's of gain-before-
feedback. Place the monitors slightly off-axis
(135-) where the microphone is least sensitive.
Frequency Management
Organization of frequency resources.
Frequency Modulation
A technology that alters (modulates) carrier
frequencies to transmit information.
Frequency Range
The frequency range of a microphone is usually
stated as the upper and lower frequency limits
within which the microphone delivers a useful
output signal.
Frequency Response
Microphones are not equally sensitive to all
notes. The frequency response indicates the
relationship between sensitivity and pitch. The
0-dB reference being the output voltage at 1
kHz, the frequency response is measured at
constant sound pressure level, from about
20 Hz (lowest note) to 20 kHz (above the upper
limit of human hearing).
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