Specifications

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GLOSSARY
Hum Sensitivity
Magnetic fields from amplifiers, long power
cables, and lighting systems in particular may
induce hum in microphones. A microphone's
hum sensitivity gives an indication of how sus-
ceptible it is to this kind of interference. Values
are 3 µV/5 µT for dynamic microphones with hum
suppression coil, 30 µV/5 µT for dynamics with
no suppression coil (D 90, D 95, D 190), and up
to 10 µV/5 µT for condenser microphones. In
practice, though, it is the microphone cables,
most of all unbalanced ones, and mixer inputs,
that are most likely to pick up hum.
Impedance
Frequency dependent AC resistance of a micro-
phone. Always quoted at 1 kHz the actual
impedance at other frequencies may differ
slightly from this reference value. Also known
as “source impedance”.
Intercept Point
The Intercept Point (IP) provides a measure for
an amplifier's resistance to intermodulation
distortion. IP 3, for example, is the reciprocal
value of the third-order coefficient of an ampli-
fier's nonlinear transmission polynomial.
Interference
Disturbance in transmission caused by extra-
neous signals.
Intermodulation
A nonlinear (multiplicative) combination of sig-
nals with different carrier frequencies that will
produce completely new frequencies, called
intermodulation products.
Limiter
Electronic circuit that prevents subsequent cir-
cuits being overloaded by excessive signal lev-
els that would also cause distortion.
Line Microphone
The directivity factor of conventional unidirec-
tional microphones is limited by the laws of
physics. This can be overcome by installing a
slotted tube in front of the diaphragm (“inter-
ference tube”). Off-axis sounds are canceled
through interference, which results in an ultra-
directional polar pattern.
Matching
Microphones should operate in an open circuit.
This is the case if the input impedance of the
preamplifier or mixer is at least 2 to 5 times as
high as the microphone's rated impedance. The
appropriate value is quoted in the specifica-
tions of each microphone as “recommended
load impedance”.
Maximum SPL
The highest sound pressure level (loudness) a
microphone can handle without introducing
more than a specified amount of “Total
Harmonic Distortion” (1 %), in other words,
without distorting the signal. Usually measured
at 1 kHz, except for the C 480 B ULS Series
where it is quoted from 30 Hz to 20 kHz.
Mechanical Noise
See “Vibrational Noise”.
Memory Effect
The loss of capacity which occurs in nickel-
cadmium storage batteries if they are not com-
pletely discharged prior to recharging.
Modulation and Demodulation
A sine-wave carrier starting at a time of minus
infinity and ending at a time of plus infinity
contains no information. However, any change
in amplitude or frequency at any time (e.g., a
pulse-like change) adds information to the car-
rier. This process is called “modulation”. The
process by which a receiver detects and
extracts this information from the carrier is
called “demodulation”.
Multichannel System
A wireless microphone system that allows sev-
eral radio microphones to be operated simulta-
neously in the same room.
Noise Burst
Brief disruption of the desired signal by noise
from a transient interference source (e.g., igni-
tion spark).
Noise Skirt
An ideal carrier spectrum would be a line. As
the carrier is modulated, the noise inherent in
the switching signals makes the transients
look ragged. This raggedness ultimately fre-
quency-modulates the carrier with noise.
Once that happens, the carrier spectrum is no
longer a line but a noise spectrum that tapers
off to either side of the wanted frequency,
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