BRUEL & KJAER 4188 User manual

Brüel&Kjær
BK
BA5105–12
Technical
Documentation
WORLD HEADQUARTERS: DK-2850 Nærum • Denmark •
Telephone: [phone] •Telex: 37316 bruka dk • Fax: [phone] •
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Microphone Handbook
For the Falcon™ Range of Microphone Products

Revision February 1995
BA5105–12
Brüel & Kjær Falcon™ Range of Microphone Products
Microphone Handbook
Microphone Handbook

0−2Brüel & KjærFalcon™ Range of Microphone Products
Microphone Handbook
Trademarks
Microsoft is a registered trademark and Windows is a trademark of Microsoft Cor-
poration.
Copyright © 1994, 1995, Brüel&Kjær A/S
All rights reserved. No part of this publication may be reproduced or distributed in
any form or by any means without prior consent in writing from Brüel & Kjær A/S,
Nærum, Denmark.

Falcon™ Range of Microphone Products
Microphone Handbook
BE1373–12 0−3
Contents
1. Introduction....................................................................................................................... 1–1
1.1 About the Microphone Handbook............................................................................... 1–2
1.2 About the Falcon™ Range of Microphone Products.................................................. 1–2
1.3 The Microphones......................................................................................................... 1–2
1.4 The Preamplifiers........................................................................................................ 1–8
2. Prepolarized Free-field 1/2" Microphone Type 4188....................... 2–1
2.1 Introduction................................................................................................................. 2–2
2.2 Sensitivity.................................................................................................................... 2–4
2.3 Frequency Response.................................................................................................... 2–5
2.4 Directional Characteristics....................................................................................... 2–13
2.5 Dynamic Range ......................................................................................................... 2–16
2.6 Equivalent Volume and Calibrator Load Volume ................................................... 2–19
2.7 Capacitance ............................................................................................................... 2–20
2.8 Polarization Voltage.................................................................................................. 2–20
2.9 Leakage Resistance................................................................................................... 2–21
2.10 Stability ..................................................................................................................... 2–21
2.11 Effect of Temperature ............................................................................................... 2–22
2.12 Effect of Ambient Pressure....................................................................................... 2–25
2.13 Effect of Humidity..................................................................................................... 2–26
2.14 Effect of Vibration ..................................................................................................... 2–27
2.15 Effect of Magnetic Field............................................................................................ 2–27
2.16 Electromagnetic Compatibility................................................................................. 2–27
2.17 Specifications Overview............................................................................................ 2–28
2.18 Ordering Information................................................................................................ 2–28
3. Prepolarized Free-field 1/2" Microphone Type 4189....................... 3–1
3.1 Introduction................................................................................................................. 3–2
3.2 Sensitivity.................................................................................................................... 3–5
3.3 Frequency Response.................................................................................................... 3–6
3.4 Directional Characteristics....................................................................................... 3–14
3.5 Dynamic Range ......................................................................................................... 3–15
3.6 Equivalent Volume and Calibrator Load Volume ................................................... 3–18
3.7 Capacitance ............................................................................................................... 3–20
3.8 Polarization Voltage.................................................................................................. 3–20
3.9 Leakage Resistance................................................................................................... 3–21
3.10 Stability ..................................................................................................................... 3–21

Falcon™ Range of Microphone Products
Microphone Handbook Brüel & Kjær
0−4
Contents
3.11 Effect of Temperature............................................................................................... 3–22
3.12 Effect of Ambient Pressure....................................................................................... 3–25
3.13 Effect of Humidity..................................................................................................... 3–26
3.14 Effect of Vibration..................................................................................................... 3–27
3.15 Effect of Magnetic Field............................................................................................ 3–27
3.16 Electromagnetic Compatibility................................................................................. 3–27
3.17 Specifications Overview............................................................................................ 3–28
3.18 Ordering Information................................................................................................ 3–28
4. Free-field 1/2" Microphone Type 4190......................................................... 4–1
4.1 Introduction................................................................................................................. 4–2
4.2 Sensitivity.................................................................................................................... 4–5
4.3 Frequency Response.................................................................................................... 4–6
4.4 Directional Characteristics....................................................................................... 4–13
4.5 Dynamic Range ......................................................................................................... 4–14
4.6 Equivalent Volume and Calibrator Load Volume ................................................... 4–17
4.7 Capacitance ............................................................................................................... 4–19
4.8 Polarization Voltage.................................................................................................. 4–19
4.9 Leakage Resistance................................................................................................... 4–21
4.10 Stability ..................................................................................................................... 4–21
4.11 Effect of Temperature............................................................................................... 4–22
4.12 Effect of Ambient Pressure....................................................................................... 4–25
4.13 Effect of Humidity..................................................................................................... 4–27
4.14 Effect of Vibration..................................................................................................... 4–27
4.15 Effect of a Magnetic Field......................................................................................... 4–27
4.16 Electromagnetic Compatibility................................................................................. 4–28
4.17 Specifications Overview............................................................................................ 4–28
4.18 Ordering Information................................................................................................ 4–28
5. Free-field 1/2" Microphone Type 4191......................................................... 5–1
5.1 Introduction................................................................................................................. 5–2
5.2 Sensitivity.................................................................................................................... 5–5
5.3 Frequency Response.................................................................................................... 5–6
5.4 Directional Characteristics....................................................................................... 5–13
5.5 Dynamic Range ......................................................................................................... 5–14
5.6 Equivalent Volume and Calibrator Load Volume ................................................... 5–17
5.7 Capacitance ............................................................................................................... 5–19
5.8 Polarization Voltage.................................................................................................. 5–19
5.9 Leakage Resistance................................................................................................... 5–21
5.10 Stability ..................................................................................................................... 5–21
5.11 Effect of Temperature............................................................................................... 5–22
5.12 Effect of Ambient Pressure....................................................................................... 5–25
5.13 Effect of Humidity..................................................................................................... 5–27
5.14 Effect of Vibration..................................................................................................... 5–27
5.15 Effect of Magnetic Field............................................................................................ 5–27

Falcon™ Range of Microphone Products
Microphone Handbook
BE1373–12 0−5
Contents
5.16 Electromagnetic Compatibility................................................................................. 5–28
5.17 Specifications Overview............................................................................................ 5–28
5.18 Ordering Information................................................................................................ 5–28
6. Pressure-field 1/2" Microphone Type 4192.............................................. 6–1
6.1 Introduction................................................................................................................. 6–2
6.2 Sensitivity.................................................................................................................... 6–5
6.3 Frequency Response.................................................................................................... 6–6
6.4 Directional Characteristics....................................................................................... 6–13
6.5 Dynamic Range ......................................................................................................... 6–14
6.6 Equivalent Volume and Calibrator Load Volume ................................................... 6–17
6.7 Capacitance ............................................................................................................... 6–19
6.8 Polarization Voltage.................................................................................................. 6–19
6.9 Leakage Resistance................................................................................................... 6–21
6.10 Stability ..................................................................................................................... 6–21
6.11 Effect of Temperature ............................................................................................... 6–22
6.12 Effect of Ambient Pressure....................................................................................... 6–25
6.13 Effect of Humidity..................................................................................................... 6–27
6.14 Effect of Vibration ..................................................................................................... 6–27
6.15 Effect of Magnetic Field............................................................................................ 6–27
6.16 Electromagnetic Compatibility................................................................................. 6–28
6.17 Specifications Overview............................................................................................ 6–28
6.18 Ordering Information................................................................................................ 6–28
7. Low-frequency Pressure-field 1/2" Microphone Type 4193....... 7–1
7.1 Introduction................................................................................................................. 7–2
7.2 Sensitivity.................................................................................................................... 7–5
7.3 Frequency Response.................................................................................................... 7–7
7.4 Directional Characteristics....................................................................................... 7–15
7.5 Dynamic Range ......................................................................................................... 7–16
7.6 Equivalent Volume and Calibrator Load Volume ................................................... 7–20
7.7 Capacitance ............................................................................................................... 7–22
7.8 Polarization Voltage.................................................................................................. 7–22
7.9 Leakage Resistance................................................................................................... 7–24
7.10 Stability ..................................................................................................................... 7–24
7.11 Effect of Temperature ............................................................................................... 7–26
7.12 Effect of Ambient Pressure....................................................................................... 7–28
7.13 Effect of Humidity..................................................................................................... 7–30
7.14 Effect of Vibration ..................................................................................................... 7–30
7.15 Effect of Magnetic Field............................................................................................ 7–30
7.16 Electromagnetic Compatibility................................................................................. 7–31
7.17 Specifications Overview............................................................................................ 7–31
7.18 Ordering Information................................................................................................ 7–32

Falcon™ Range of Microphone Products
Microphone Handbook Brüel & Kjær
0−6
Contents
8. 1/2" Microphone Preamplifier Type 2669................................................. 8–1
8.1 Introduction................................................................................................................. 8–2
8.2 Frequency Response.................................................................................................... 8–4
8.3 Dynamic Range ........................................................................................................... 8–5
8.4 Phase Response........................................................................................................... 8–8
8.5 Effect of Temperature................................................................................................. 8–8
8.6 Effect of Magnetic Fields ............................................................................................ 8–9
8.7 Electromagnetic Compatibility (EMC)....................................................................... 8–9
8.8 Brüel&Kjær’s Patented Charge-injection Calibration Technique......................... 8–10
8.9 Specifications Overview............................................................................................ 8–11
8.10 Ordering Information................................................................................................ 8–11
9. Accessories......................................................................................................................... 9–1
9.1 Accessories Available.................................................................................................. 9–2
Index

Falcon™ Range of Microphone Products
Microphone Handbook
BE1372–12 1−1
Chapter 1
Introduction

Chapter 1 — Introduction
About the Microphone Handbook
Falcon™ Range of Microphone Products
Microphone Handbook Brüel & Kjær
1−2
1.1 About the Microphone Handbook
This handbook contains specific information about Brüel&Kjær’s Falcon™ Range of
1/2" microphone products. It contains a chapter on each of the microphones, a chap-
ter on 1/2" Microphone Preamplifier Type 2669 which can be used with these micro-
phones, and a list of the available accessories which can also be used with these
microphones.
1.2 About the Falcon™ Range of Microphone Products
Brüel&Kjær’s FalconRange of microphone products includes six 1/2" condenser
microphones and a microphone preamplifier covering, between them, a very wide
range of needs and applications.
They are the culmination of over 40 years of leadership in top quality condenser
microphones and preamplifiers for precision acoustic measurements. The Falcon
Range of microphone products will meet your demands whether they be in comply-
ing with ANSI or IEC standards or in acoustic research.
1.3 The Microphones
1.3.1 Robust and Stable
The microphones in the FalconRange are robust and can even withstand an IEC
68-2-32 1m drop test onto a hard wooden block without suffering more than
±0.1dB change in sensitivity. They are made of carefully selected materials and
alloys to ensure excellent stability and are virtually unaffected by industrial and
similarly hostile environments. During manufacture, each microphone is artificially
aged at a high temperature to ensure good long-term stability. As a result of all
this, Brüel&Kjær has extended their warranty period to three years.
No ecologically damaging materials are used in the manufacture and packaging of
these microphones.
1.3.2 Selecting a Microphone for Your Needs
To make sure you select the right microphone to match your needs, you will proba-
bly have to consider one or more of the following:
●Standards (IEC or ANSI)
●Frequency range
●Polarization
●Sound field.

Chapter 1 — Introduction
The Microphones
Falcon™ Range of Microphone Products
Microphone Handbook
BE1372–12 1−3
The following, together with the flow chart shown in Fig.1.1 and the comparitive
list of specifications shown in Table 1.2, will help you to make your decision.
Measurement Standards
You can use these microphones in noise measurement systems satisfying either
ANSI or IEC standards (or their local equivalents). The microphones use only 50%
to 70% of the tolerances allowed by these standards.
Frequency Ranges
All six microphones cover the audio frequency range. If, however, you want to meas-
ure at frequencies down to 0.07Hz (for infrasound measurements), choose Low-
frequency Pressure-field 1/2" Microphone Type 4193, or at frequencies up to 40kHz
(for harmonic distortion measurements on loudspeakers) choose Free-field 1/2" Mi-
crophone Type 4191.
Polarization/Preamplifier
Prepolarized microphones are required on certain portable sound level meters
(which do not provide external polarization) and are a good choice in tough and
Fig.1.1 Flow chart to help you choose the right microphone in the Falcon™ Range for your needs
940369e
Start
ANSI
S 1.4 1983
Type 1 
or S 1.12
Type M
No
Yes
IEC Pressure-
field Free-
field
Audio
freq.
No
Extended
freq.
Yes
Type 1
Type 0
and
Type 1
S 1.4
Type 0
Type 1
External
Polarization
Audio freq. or
Extended freq.
Free-field
or
Pressure-field
Infrasound
Standards
ANSI
or
IEC 651
Frequency
Analysis
No No
4188
4189
Yes Yes
41904191419241934188
4189
4190
4191
4192
4193
4188 + DZ 9566
4191
4192
4193
S 1.12

Chapter 1 — Introduction
The Microphones
Falcon™ Range of Microphone Products
Microphone Handbook Brüel & Kjær
1−4
humid environments. Externally polarized microphones are more stable, also at
high temperatures. All can be used with Brüel&Kjær’s 1/2" Microphone Preamplifi-
er Type 2669. The two prepolarized microphones (Types 4188 and 4189) can also be
used with Brüel&Kjær’s Preamplifier Type 2671.
Free-field Response or Pressure-field Response
The four free-field response microphones (Types 4188 to 4191) cover specific IEC
requirements and should be used in sound fields where reflections are negligible.
The two pressure-field response microphones (Types 4192 and 4193) should be used
for measurements in acoustic couplers. They also cover specific ANSI requirements
and can be used in diffuse sound fields.
As Replacements for Traditional Brüel&Kjær Microphones
Table 1.1 shows what traditional Brüel&Kjær microphones (type approval permit-
ting) can be replaced by microphones from the FalconRange.
Microphone Specifications
The design and construction of each microphone results in a reliable transducer of
high sensitivity and low temperature dependence. Most of the data given for the
microphones in this handbook are for open-circuit conditions, which means that the
microphone looks into an infinitely high impedance. Table 1.2 summarises the most
important specifications for the microphones in the FalconRange. In practice,
however, a microphone is used with a preamplifier which slightly influences the
given responses. When you use a Brüel&Kjær preamplifier (for example, 1/2" Micro-
phone Preamplifier Type 2669), the input impedance is very high (high resistance,
low capacitance), and the loading on the microphone cartridge is insignificant.
Traditional Microphone FalconRange
4155 4189
4165 4190
4133/4149 4191
4134 4192
4147 4193
4166 4188*/4190*/4192*
4176 4188*/4189*
Table 1.1 Replacement of traditional Brüel&Kjær microphones
with ones from the Falcon™ Range

Chapter 1 — Introduction
The Microphones
Falcon™ Range of Microphone Products
Microphone Handbook
BE1372–12 1−5
Specification Type 4188 Type 4189 Type 4190 Type 4191 Type 4192 Type 4193
Description Prepolarized Free-
field Prepolarized Free- field Low Noise Free-field Free-field Pressure-field Infrasound,
Pressure-field
Nominal
Open-circuit
Sensitivity 31.6mV/Pa 50mV/Pa 50mV/Pa 12.5mV/Pa 12.5mV/Pa 12.5mV/Pa
Polarization
Voltage 0 0 200 200 200 200
Optimized
Frequency
Response
±1dB:
12.5Hz to 8kHz
±2dB:
8Hz to 12.5kHz
±1dB:
10Hz to 8kHz
±2dB:
6.3 Hz to 20 kHz
±1dB:
5Hz to 10kHz
±2dB:
3.15Hz to 20kHz
±1dB:
5Hz to 16kHz
±2dB:
3.15Hz to 40kHz
±1dB:
5Hz to 12.5kHz
±2dB:
3.15Hz to 20kHz
±1dB:
0.12Hz to12.5 kHz
±2dB:
0.07Hz to 20kHz
Main
Standards IEC 651 Type 1,
ANSI S1.4 1983 IEC 651 Type 1 IEC 651 Type 0 and Type 1
IEC 651 Type 0
and Type 1, ANSI
S1.12 Type M
ANSIS1.4 Type1,
ANSI S1.12 Type
M
ANSI S1.4 Type 1,
ANSI S1.12 Type
M
Lower Limiting
Freq. (–3dB) 1to 5Hz 2 to 4Hz 1 to 2Hz 1 to2Hz 1 to 2Hz 10 to 50mHz
Diaphragm
Resonance
Frequency 9kHz 14kHz 14kHz 34kHz 23kHz 23kHz
Inherent Noise 14.2dB(A)
14.5dB(Lin) 14.6dB(A) 15.3dB(Lin) 14.5dB(A) 15.5dB(Lin) 20.0dB(A) 21.4dB(Lin) 19.0dB(A) 21.3dB(Lin) 19.0 dB(A) 21.3dB(Lin)
3% Distortion
Limit 146dB 146dB 148dB 162dB 162dB 162dB
Maximum SPL
(Peak) 157dB 158dB 159dB 171dB 171dB 171dB
Nominal
Capacitance 12pF 14pF 16pF 18pF 18pF 18pF
Equivalent
Volume 65 mm346mm346mm311.6mm38.8mm38.8mm3
Calibrator Load
Volume 208mm3260mm3250mm3190mm3190mm3190mm3
Pistonphone
4228 Correction
(with DP 0776) +0.02dB 0.00dB 0.00 dB +0.02dB +0.02dB +0.02dB
Operating
Temperature
Range
–30 to 125°C
(–22 to 257°F)
(up to 70°C with
corrector)
–30 to 150°C
(–22 to 302°F)
–30 to 150°C (–22 to 302°F)
(can be used up to +300°×C (572 °F) but with a permanent sensitivity change
of typically +0.4dB which stabilises after one hour)
Temperature
Coefficient +0.005dB/°C –0.001dB/°C–0.007dB/°C –0.002dB/°C –0.002dB/°C–0.002dB/°C
Pressure
Coefficient –0.021dB/kPa –0.010dB/kPa –0.010dB/kPa –0.007dB/kPa –0.005dB/kPa –0.005dB/kPa
Operating
Humidity Range 0 to 100%RH (without condensation)
Effect of
Humidity <0.1dB/100%RH
Effect of
Vibration (SPL
with axial 1m/s2)63.5dB 62.5dB 62.5 dB 65.5dB 65.5dB 65.5 dB
Effect of
Magnetic Field
(SPLwith80A/m,
50Hz field)
7dB 6dB 4dB 16dB 16dB 16dB
Table 1.2 Comparision of main specifications for the different microphones in the Falcon™ Range

Chapter 1 — Introduction
The Microphones
Falcon™ Range of Microphone Products
Microphone Handbook Brüel & Kjær
1−6
1.3.3 Physical Dimensions
1.3.4 Calibration
For general routine calibration you can check the sensitivity at 1kHz with Sound
Level Calibrator Type 4231, or at 250Hz with Pistonphone Type 4228. For a thor-
ough calibration, Multifunction Acoustic Calibrator Type 4226 allows you to meas-
ure both sensitivity and frequency response.
An in-situ check, which also takes the state of the microphone into account, is
Brüel&Kjær’s Charge-Injection Calibration technique which is a patented feature
of 1/2" Microphone Preamplifier Type 2669 (see Chapter 8).
Dimensions
(mm) Type 4188 Type 4189 Type 4190 Type 4191 Type 4192 Type 4193
Microphone
Length (with
grid) 14.9 17.6 17.6 13.5 13.5 13.5
Housing
Length (with-
out grid) 14.0 16.3 16.3 12.6 12.6 12.6
Housing
Diameter
(±0.03mm) 12.7 12.7 12.7 12.7 12.7 12.7
Housing
Front-end
Length 6.46.26.26.16.16.1
Diaphragm
Ring Diameter 12.0 12.0 12.0 12.0 12.0 12.0
Depth to Cen-
tre Terminal 4.64.64.64.64.64.6
Preamplifer
Thread
(60UNS–2) 11.7 11.7 11.7 11.7 11.7 11.7
Preamplifer
Thread Length 3.03.53.53.53.53.5
Protection
Grid Thread
(60UNS–2) 12.7 12.7 12.7 12.7 12.7 12.7
Protection
Grid Diameter
(±0.02mm) 13.2 13.2 13.2 13.2 13.2 13.2
Table 1.3 Dimensions of the different microphones in the Falcon™ Range

Chapter 1 — Introduction
The Microphones
Falcon™ Range of Microphone Products
Microphone Handbook
BE1372–12 1−7
1.3.5 Microphone-data Disk
Introduction
A 31/2" data disk which supplements the calibration chart is supplied with all mi-
crophones in the FalconRange except Prepolarized Free-field 1/2" Microphone
Type 4188.
It contains calibration data in the \DATA directory and a presentation program,
Brüel&Kjær Microphone Viewer, in the root directory. The calibration data on each
disk is described in the relevant chapters of the handbook. The Brüel&Kjær Micro-
phone Viewer program must be installed on your computer’s hard disk before use
using the installation program SETUP.EXE supplied on the data disk (see below).
Computer Requirements
Brüel&Kjær Microphone Viewer requires:
●Windows™ version 3.1 installed on your computer
●31/2" 1.4Mbyte disk drive
●1.5Mbytes free disk space
●VGA or SVGA display (minimum 640×480 pixels)
Installing Brüel&Kjær Microphone Viewer
1. Insert the data disk in drive A.
2. Start Windows.
3. Click on the File menu in the Program Manager.
4. Select Run and type A:\SETUP.EXE.
5. Click on OK.
6. When SETUP.EXE asks you where you want to install the program, click on
OK.
Unless you have selected another directory, SETUP.EXE installs the program in
C:\BK–MIC. Two files (VBRUN300.DLL and VER.DLL) are installed in the
\WINDOWS\SYSTEM directory. These files are common for Visual Basic pro-
grams and can also be used by other programs.
About Brüel&Kjær Microphone Viewer
Brüel&Kjær Microphone Viewer shows the individual microphone’s data supplied
on the data disk in either graphical or tabular form.

Chapter 1 — Introduction
The Preamplifiers
Falcon™ Range of Microphone Products
Microphone Handbook Brüel & Kjær
1−8
When the program is started from Windows™, the calibration data in the \DATA
directory of the disk in the A drive is shown. If no data is found, the Open box
automatically appears. Select the Sensitivity file to access all data associated with
the microphone. Selecting a Result or Work file will only give you access to that
particular response.
The data can be copied to the hard disk using the Copy Microphone Data function
in the File menu. Individual data files are named with the microphone’s serial
number to prevent file name conflicts with data files from other microphones.
The data shown can also be printed out or copied to the clipboard for further
processing in spreadsheets and text editors.
When a Sensitivity file is selected, all frequency responses are obtained by adding
the relevant corrections and the low-frequency response to the actuator response.
Any additional information about Brüel&Kjær Microphone Viewer can be seen in
the README.TXT file. In addition, help in the form of hypertext is included
throughout to guide you.
1.4 The Preamplifiers
The 1/2" Microphone Preamplifier Type 2669 has been developed for making preci-
sion acoustic measurements with Brüel&Kjær’s wide range of condenser micro-
phones. You can connect 1/2" microphones directly and 1", 1/4" and 1/8" types using
adaptors.
The preamplifier, cable and its connectors all fulfil EMC requirements.
You can verify the condition of the microphone, preamplifier and cable in-situ using
Brüel&Kjær’s patented Charge-injection Calibration technique. This means that
you can detect defects in the entire measurement set-up, including the microphone.
The preamplifier’s low output impedance allows long extension cables to be used
without problems.
The robust, compact design means that you can use the 1/2"Microphone Preamplifi-
er Type 2669 over a wide range of environmental conditions. The cable, which you
can detach from the preamplifier, is very thin but strong and remains flexible down
to –20°C.
The 1/2" Microphone CCLD Preamplifier Type 2671 has been developed for use with
prepolarised microphones in mind.
Full details of the 1/2" Microphone CCLD Preamplifier Type 2671 are available in
the 2671 Product Data Sheet.

Falcon™ Range of Microphone Products
Microphone Handbook
BE1374–12 2−1
Chapter 2
Prepolarized Free-field 1/2" Microphone
Type 4188

Chapter 2 — Prepolarized Free-field 1/2" Microphone Type 4188
Introduction
Falcon™ Range of Microphone Products
Microphone Handbook Brüel & Kjær
2−2
2.1 Introduction
2.1.1 Description
Prepolarized Free-field 1/2" Microphone Type 4188 is a prepolarized 1/2" 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. It is suited to IEC 651 Type 1 measurements
and, when fitted with the supplied Random Incidence Corrector DZ9566, is also
suited to ANSI S 1.4–1983 Type 1 measurements.
The 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.
This 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.
It is supplied with a calibration chart.
Fig.2.1 Prepolarized Free-field 1/2" Microphone Type 4188 with Protection Grid DD0525 (included)

Chapter 2 — Prepolarized Free-field 1/2" Microphone Type 4188
Introduction
Falcon™ Range of Microphone Products
Microphone Handbook
BE1374–12 2−3
2.1.2 The Calibration Chart
Each microphone is supplied with an individual calibration chart (see Fig.2.2)
which gives the microphone’s open-circuit pressure sensitivity together with the
typical capacitance and free-field and random-incidence frequency responses*. When
these are combined with the microphone’s typical data supplied in this chapter, the
individual microphone’s response under various conditions can be determined.
Open-circuit Sensitivity
The stated open-circuit pressure sensitivity is valid at the reference frequency
(1000Hz) for random-incidence and pressure-field conditions. The free-field sensitiv-
ity at the reference frequency (1000Hz) is 0.11dB higher than the pressure sensi-
tivity.
Ambient Conditions
The ambient conditions are measured continuously during calibration at the factory.
The calibration results obtained at the measured environmental calibration condi-
tions are corrected to the stated reference ambient conditions (23°C, 101.325kPa
and 50%RH).
Frequency Responses
Two typical frequency responses are shown on the calibration chart. Both are nor-
malized to 0dB at the reference frequency (1000Hz).
The left-hand curve on the rear side of the calibration chart is the open-circuit 0°-
incidence free-field response for the microphone without the supplied Random Inci-
dence Corrector DZ9566.
*Random-incidence response with supplied Random Incidence Corrector DZ9566.
Fig.2.2 Microphone calibration chart (front and back)
Brüel & Kjær
Caution: Static electricity discharge directly on the centre terminal may damage the prepolarization of the
cartridge. Therefore, ensure that the housing of the cartridge makes contact before the centre terminal.
Sensitivity: The loaded sensitivity is typically 0.05dB lower than the sensitivity stated. The random-field
sensitivity is the same as the pressure sensitivity. The free-field sensitivity at 1000Hz is 0.15dB higher
than the pressure sensitivity.
Free-field calibration with Sound Level Calibrators at 1000Hz: Adjust the Sound Level Meter, or other
measurement equipment, to indicate 0.15dB lower SPL than the actual SPL produced by the calibrator.
The two grooves means “prepolarized”, i.e. 0V external polarization voltage.
Refer to the 4188 Product Data for further information. See also rear side.
Prepolarized Condenser Microphone Cartridge Type 4188 
Serial No.:

Open-circuit Pressure Sensitivity at 1013 hPa 23˚C and 50% RH:
dB re 1 V/Pa or mV/Pa
Frequency: 1000Hz Capacitance: 12pF (typical)
Polarization Voltage (external): 0V
Date: Signature: .......................................
BK
7/6-'89
BC0211-11
930776e
-3
-2
-1
0
1
2
3
12 51020 50 100 200 500 1k 2k 5k 10k 20k
Typical random-field response with random incidence corrector
Frequency response satisfies ANSI S 1.4–1984 Type 1
-3
-2
-1
0
1
2
3
12 51020 50 100 200 500 1k 2k 5k 10k 20k
Typical free-field response for 0˚ incidence
without random incidence corrector
Tol.
Tol.
Tol.
Tol.
Frequency response satisfies IEC 651 Type 1
1. July 1993
–30.2
1740259
30.9
N.G.

Chapter 2 — Prepolarized Free-field 1/2" Microphone Type 4188
Sensitivity
Falcon™ Range of Microphone Products
Microphone Handbook Brüel & Kjær
2−4
The right-hand curve on the rear side of the calibration chart is the open-circuit
random-incidence response for the microphone with the supplied Random Incidence
Corrector DZ9566.
Each microphone’s individual lower limiting frequency is measured to ensure that it
is within the specified tolerances (see Fig.2.3).
2.1.3 Recommended Recalibration Interval
With normal handling of the microphone and any associated instrument,
Brüel&Kjær recommends that the microphone be recalibrated every 2 years.
Prepolarized Free-field 1/2" Microphone Type 4188 is very stable over this period
(see section 2.10 to section 2.12). Improper handling is by far the most likely cause
of change in the microphone’s properties. Any damage which causes improper oper-
ation can probably be detected using a sound level calibrator. In many cases, the
damage can be seen by carefully inspecting the protection grid and diaphragm.
2.2 Sensitivity
2.2.1 Open-circuit Sensitivity
The open-circuit sensitivity is defined as the sensitivity of the microphone when not
loaded by the input impedance of the connected preamplifier (the termination is
described in IEC1094–2). The sensitivity is measured for the individual microphone
at 1000Hz and stated on the microphone’s calibration chart (see section 2.1.2). The
nominal sensitivity is shown in Table 2.1.
2.2.2 Loaded Sensitivity
When loaded by a preamplifier, the sensitivity of the microphone is given by:
(2.1)
where SC= overall sensitivity of microphone and preamplifier combination
SO= open-circuit sensitivity of microphone
G= voltage gain of microphone and preamplifier combination (in dB)
Nominal open-circuit sensitivity Accepted Deviation
(dB)
mV/Pa dB re 1V/Pa
31.6 –30 ±2
Table 2.1 Nominal open-circuit sensitivity
S
C
S
O
G
+=

Chapter 2 — Prepolarized Free-field 1/2" Microphone Type 4188
Frequency Response
Falcon™ Range of Microphone Products
Microphone Handbook
BE1374–12 2−5
With Microphone Preamplifier Type 2639: G= –0.15dB
With 1/2" Microphone Preamplifier Type 2669: G= –0.30dB
Example
Loaded sensitivity of typical microphone with 1/2" Microphone Preamplifier Type
2669:
SC= –29.8 + (–0.30) = –30.1dB
2.2.3 K-factor
Some types of Brüel&Kjær instruments use the K-factor (correction factor) or the
KO-factor (open-circuit correction factor) for calibration.
(2.2)
(2.3)
Example
Correction factor for typical microphone with 1/2" Microphone Preamplifier Type
2669:
K= –26 – (–30.1) = +4.1dB
Open-circuit correction factor for typical microphone with 1/2" Microphone Preampli-
fier Type 2669:
KO= –26 – (–29.8) = +3.8dB
2.3 Frequency Response
2.3.1 General
In acoustic measurements, there are three types of sound field:
●Free field
●Pressure field
●Diffuse field
The microphone is optimized to have a flat frequency response in one of these
sound fields. This response is called the optimized response. A microphone’s re-
sponse in a diffuse field is equivalent to its random-incidence response.
K
26
–
SC
–=
K
O26
–
S
O
–=