Chapter 7 — Low-frequency Pressure-field
1
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" Microphone Type 4193
Introduction
Falcon™ Range of Microphone Products
Microphone Handbook
Brüel & Kjær
7
−
4
Frequency Responses
Two frequency responses are shown on the calibration chart. Both are normalized
to 0dB at the reference frequency (251.2Hz
*
).
The lower curve on the calibration chart is the individual microphone’s open-circuit
pressure-field response. This response is the optimized response for Low-frequency
Pressure-field
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2
" Microphone Type 4193.
The upper curve on the calibration chart is the random-incidence response.
Both curves are determined by adding the relevant correction curve to the individu-
al actuator response measured with Electrostatic Actuator UA0033. The individual
microphone’s electrostatic actuator response is also available on the data disk.
The dotted part of the curve is the typical low-frequency response. Each micro-
phone’s individual lower limiting frequency is measured to ensure that it is within
the specified tolerances (see Fig.7.3).
7.1.3 Data Disk
The 3
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2
" data disk supplied with each microphone supplements the calibration
chart. It contains individual calibration data and correction curves (see Table 7.1)
with a frequency resolution of
1
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12
-octave as comma-separated ASCII text files un-
der the \DATA directory.
a. Individual calibration data (measured).
b. Low-frequency response combined with actuator response and free-field corrections.
c. Typical response for Low-frequency Pressure-field
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2
" Microphone Type 4193.
d. Corrections for Low-frequency Pressure-field
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" Microphone Type 4193.
File Name Content Frequency Range
S#######.BKM
a
Sensitivity calibration 251.2Hz
A#######.BKM
a
Actuator response 200 Hz – 22 kHz
P#######.BKR
b
Pressure-field response 1 Hz – 22 kHz
4193L.BKT
c
Low-frequency response 1 Hz – 190 Hz
4193F.BKC
d
Free-field corrections without protection grid 200 Hz – 22 kHz
4193FG.BKC
d
Free-field corrections with protection grid 200 Hz – 22kHz
4193R.BKC
d
Random-incidence corrections without protection grid 200 Hz – 22kHz
4193RG.BKC
d
Random-incidence corrections with protection grid 200 Hz – 22 kHz
4193P.BKC
d
Pressure-field corrections 200 Hz – 22 kHz
Table 7.1 Calibration data and corrections contained on the data disk. Note: ####### is the micro-
phone’s serial number
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