BRUEL & KJAER 4188 - Frequency Response

Chapter 3 — Prepolarized Free-field
1
/
2
" Microphone Type 4189
Frequency Response
Falcon™ Range of Microphone Products
Microphone Handbook
Brüel & Kjær
3
−
6
Example
Loaded sensitivity of typical microphone with
1
/
2
" Microphone Preamplifier Type
2669:
S
C
= –26.3 + (–0.25) = –26.55dB
3.2.3 K-factor
Some types of Brüel&Kjær instruments use the K-factor (correction factor) or the
K
O
-factor (open-circuit correction factor) for calibration.
(3.2)
(3.3)
Example
Correction factor for typical microphone with
1
/
2
" Microphone Preamplifier Type
2669:
K = –26 – (–26.55) = +0.55dB
Open-circuit correction factor for typical microphone with
1
/
2
" Microphone Preampli-
fier Type 2669:
K
O
= –26 – (–26.3) = +0.3dB
3.3 Frequency Response
3.3.1 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 3.3.4 is common for all types of response.
K
26
–
S
C
–=
K
O
26
–
S
O
–=