3
Prepolarization
They are prepolarized by a fixed, neg-
atively charged layer deposited on
the backplate of the microphone. If,
however, an external polarization
voltage is mistakenly applied, no per-
manent damage will occur because
this will cause the backplate to repel
the microphone’s diaphragm.
The housing of these prepolarized
microphones are marked by a pair of
parallel grooves.
Static Pressure Equalization
Table 2
tells you how each micro-
phone is vented for static pressure
equalisation. In brief, tall micro-
phones are rear vented and short mi-
crophones are side vented. Rear
venting permits the use of the Dehu-
midifier UA 0308 for operation in es-
pecially humid environments.
Free-field
1
/
2
″
Microphones
Types 4190 and 4191
These are externally polarized, free-
field microphones which differ main-
ly in frequency range and sensitivity.
The polarization voltage required is
200 V and is provided by the instru-
ment or analyzer powering the asso-
ciated preamplifier.
Both can be used for noise meas-
urements in accordance with the
more stringent requirements of
IEC 651 Type 0 (and off course Type
1).
Free-field
1
/
2
″
Microphone Type 4190
Has greater sensitivity and low in-
herent noise. Its frequency range is
from 3.15 Hz to 20 kHz and is very
well suited for a wide range of preci-
sion audio-frequency sound measure-
ments.
Free-field
1
/
2
″
Microphone Type 4191
Has an extended frequency range
which is from 3.15 Hz to 40 kHz. This
makes it very well suited for electro-
acoustic measurements on loud-
speakers and microphones as well as
for general precision sound measure-
ments.
Pressure-field
1
/
2
″
Microphones Types 4192
and 4193
These are externally polarized, pres-
sure-field microphones which differ
only in frequency range. The polari-
zation voltage required is 200 V and
is provided by the instrument or an-
alyzer powering the associated
preamplifier.
Both can be used for noise meas-
urements in accordance with the re-
quirements of ANSI S 1.4 1983 Type
1 and ANSI S 1.12 Type M. Note: the
sensitivity of the Type 4193 to low
frequencies can be a disadvantage if
you do not need to measure at low
frequencies.
Pressure-field
1
/
2
″
Microphone Type
4192
Has a frequency range from 3.15 Hz
to 20 kHz. It can be used either for
ANSI S 1.4 sound measurements re-
quiring random-incidence response
or for coupler measurements, e.g. in
connection with telephone and hear-
ing aid testing. Furthermore, it also
satisfies the requirements of
ANSI S 1.12 Type M.
Pressure-field
1
/
2
″
Microphone Type
4193 and Low-frequency Adaptor
UC0211
Has an extended low-frequency range
which cuts off between 10 mHz and
50 mHz. The high end of its frequency
range extends up to 20 kHz. In addi-
tion to random-field or coupler meas-
urements, it can also be used for
measuring infrasound, for example,
in ships’ engine rooms, in helicopters
and in wind-buffeted buildings.
This microphone is supplied with a
special Low-frequency Adaptor
UC 0211 which has the effect of re-
ducing the lower cut-off frequency of
the preamplifier. In the case of the
1
/
2
″
Microphone Preamplifier Type
2669, down to 0.1 Hz. It also has the
effect of reducing the microphone’s
sensitivity by 16 dB (from 12.5 to
2 mV/Pa, or from –38 to –54 dB re 1V/
Pa), increasing the thermal noise
from 19.0 dB (A) to 29.0 dB (A) and re-
ducing the 3% distortion limit from
162 dB to 148 dB.
Type
Housing
Venting
4188/4189/
4190
Tall
Rear
4191/4192/
4193
Short
Side
Table 2 Static pressure equalisation
Microphone
Response
Sensitivity
Frequency Range
Polarization
Main Standards
Type 4188
Free- and diffuse-fields
31.6 mV/Pa
8 Hz to 12.5 kHz
0 V (prepolarized)
IEC 651 Type 1, ANSI S1.4 1983
Type 4189
Free-field
50 mV/Pa
6.3 Hz to 20 kHz
0 V (prepolarized)
IEC 651 Type 1
Type 4190
Free-field
50 mV/Pa
3.15 Hz to 20 kHz
200 V
IEC 651 Type 0/1
Type 4191
Free-field
12.5 mV/Pa
3.15 Hz to 40 kHz
200 V
IEC 651 Type 0/1, ANSI S1.12 Type M
Type 4192
Pressure-field
12.5 mV/Pa
3.15 Hz to 20 kHz
200 V
ANSI S1.4 Type 1, ANSI S1.12 Type M
Type 4193
Infrasound, Press.-field
12.5 mV/Pa
70 mHz to 20 kHz
200 V
ANSI S1.4 Type 1, ANSI S1.12 Type M
Microphone
Thermal Noise
LLF (–3 dB)
3 % Distortion Limit
Temperature Coeff.
Max. Operating Temp.
Type 4188
14.2 dB (A), 14.5 dB (Lin)
1 Hz to 5 Hz
146 dB
+0.005 dB/
°
C
125
°
C (257
°
F) (70
°
C (158
°
F) with
corrector)
Type 4189
14.6 dB (A), 15.3 dB (Lin)
2 Hz to 4 Hz
146 dB
–0.001 dB/×
°
C
150
°
C (302
°
F)
Type 4190
14.6 dB (A), 15.3 dB (Lin)
1 Hz to 2 Hz
148 dB
–0.007 dB/×
°
C
Type 4191
20.0 dB (A), 21.4 dB (Lin)
1 Hz to 2 Hz
162 dB
–0.002 dB/×
°
C
150
°
C (302
°
F)
(can be used up to 300
°
C (572
°
F) but
with a permanent sensitivity change of
typ0.4 dB which stabilises after
one hour)
Type 4192
19.0 dB (A), 21.3 dB (Lin)
1 Hz to 2 Hz
162 dB
–0.002 dB/×
°
C
Type 4193
(no UC 0211)
19.0 dB (A), 21.3 dB (Lin)
10 mHz to
50 mHz
162 dB
–0.002 dB/×
°
C
Table 3 An overall view of the most important open-circuit characteristics of each microphone (LLF means lower-limiting frequency)
