Chapter 3 — Prepolarized Free-field
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" Microphone Type 4189
Introduction
Falcon™ Range of Microphone Products
Microphone Handbook
Brüel & Kjær
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3.1 Introduction
3.1.1 Description
Prepolarized Free-field
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" Microphone Type 4189 is a prepolarized
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" free-field
microphone and offers some significant advantages when used with portable instru-
ments. For example, smaller associated instruments with low power consumption
can be used. A general advantage is the improved reliability of the associated
preamplifier in humid and polluted atmospheres. These factors make this prepolar-
ized condenser microphone particularly suitable for field measurements, both out-
doors and in industrial environments. In addition, it is suited to IEC 651 Type 1
measurements and frequency analysis measurements.
This microphone is polarized by a fixed charge-carrying layer deposited on the back-
plate. This layer is negatively charged which, at low frequencies, results in a posi-
tively increasing output voltage for a positively increasing incident sound pressure.
As a prepolarized microphone, it is externally marked by a pair of grooves.
The rugged microphone is built to ensure high stability under a variety of condi-
tions. For example, the stainless steel alloy diaphragm withstands polluted industri-
al environments. The diaphragm clamping ring is firmly secured to ensure the
microphone’s reliability, even when the microphone is used without its protection
grid. When the microphone is used without its protection grid, it can be easily
flush-mounted or inserted into closed volumes as it can be supported by the dia-
phragm clamping ring, provided that a force of less than 5Newtons is applied.
Fig.3.1 Prepolarized Free-field
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" Microphone Type 4189 with Protection Grid DB3420 (included)
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