Corrections And Adjustments; The Sound Level In The Coupler - Using The Internal Signal Generator - BRUEL & KJAER 4226 User Manual

A.1 The Sound Level in the Coupler – Using the Internal Signal Generator
The following describes the corrections automatically applied to the calibration sound levels
generated in the coupler and applies only when the
Calibration.
The sound levels generated in the coupler when loaded by a Type 4180 microphone are adjusted
to account for the responses of microphones listed under "a", "b" and "c" categories when used
with a
Sound Field
therefore, no such adjustments are made.
Furthermore, in the case when
constant A-weighted sound level of 94 dB at each discrete frequency.
Table A.1 shows the corrections for 94 Inv. A, and Table A.2 shows the Free-field corrections for
microphones listed under a, b and c categories.
Table A.1 Inverted A-weighting corrections automatically applied to the Sound Level in the coupler to simulate a constant
A-weighted level of 94 dB at each discrete frequency. Valid when coupler is loaded by a Type 4180 Microphone
Frequency
31.5
(Hz)
39.4
Inv. A
Table A.2 Free-field corrections (dB) automatically applied to coupler sound levels for microphones listed. These figures are
measured with a Type 4180 pressure microphone
Microphone
Setting
31.5 – 500
a
b
Traditional
c

Corrections and Adjustments

= Free-field setting. This does not apply when the
Sound Level
63 125 250
26.2 16.1 8.6
Frequency (Hz)
1 k 2 k
0.00 0.15 0.50
0.00 0.20 0.45
0.00 0.10 0.35
Appendix A
Function
= 94 Inv. A, an additional correction simulates a
500 1 k 2 k
3.2 0.0 –1.2
4 k 8 k 12.5 k
1.35 4.50 7.35
1.05 2.80 5.60
0.95 2.60 5.05
switch on Type 4226 is set to
= Pressure,
Sound Field
4 k 8 k 12.5 k
–1.0 1.1 4.3
Microphone Type
16 k
– 4129, 4130, 4176
7.85 4155, 4165
4133, 4134, 4147,
6.75
4149
33
16 k
6.6