BRUEL & KJAER 4188 - Frequency Response

Chapter 7 — Low-frequency Pressure-field
1
/
2
" Microphone Type 4193
Frequency Response
Falcon™ Range of Microphone Products
Microphone Handbook
BE1379– 12
7
−
7
Example
Correction factor for typical microphone with
1
/
2
" Microphone Preamplifier Type
2669:
K = –26 – (–38.5) = +12.5dB
Open-circuit correction factor for typical microphone with
1
/
2
" Microphone Preampli-
fier Type 2669:
K
O
= –26 – (–38.3) = +12.3dB
7.3 Frequency Response
7.3.1 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.
This section shows the microphone’s typical free-field, pressure-field and random-
incidence responses together with the microphone’s typical actuator response ob-
tained using Electrostatic Actuator UA0033. The low-frequency response described
in section 7.3.4 is common for all types of response.
All frequency responses and correction curves shown are valid for a microphone
without Adaptor UC0211 fitted. If the adaptor is used with
1
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2
" Microphone Pream-
plifier Type 2669 to obtain an extended low-frequency response, the frequency re-
sponse from 100Hz to 10kHz will roll off by less than 0.1dB, and up to 20kHz by
less than 0.5dB.
All frequency responses and correction curves are shown with a frequency resolu-
tion of
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12
-octave.
7.3.2 Optimized Response (Pressure-field Response)
The frequency response of Low-frequency Pressure-field
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/
2
" Microphone Type 4193
meets the requirements of ANSI S1.4 -1983, Type 1 and ANSI S1.12, Type M.