BRUEL & KJAER 4226 User Manual page 42

34 Multifunction Acoustic Calibrator Type 4226 – User Manual
Table A.2 (Continued)Free-field corrections (dB) automatically applied to coupler sound levels for microphones listed.
These figures are measured with a Type 4180 pressure microphone
a
b
Falcon
c
Table A.3 Random corrections (dB) that may be added manually to the measured pressure responses
Microphone Type
4129, 4130, 4176
4155, 4165
Traditional
4133, 4134, 4147,
4149
4188
4189, 4190
Falcon
4191, 4192, 4193
When Type 4226 is used with its own internal signal generator, the accuracy of the corrected
sound level generated in the coupler is assured for microphones listed under a, b and c
categories. The basic formula for the actual sound level (LC) generated in the coupler loaded by
a Type 4180 microphone is:
L = L
C Sound Level
where:
: is the level indicated by the setting the
L
Sound Field
: is the adjustment for free-field response (see Table A.2)
C
field
: is the correction for inverse A-weighting (Table A.1) otherwise 0 dB
C
W
Example:
switch set to 94 dB Inv. A
Sound Level
switch set to Free-field Traditional
Sound Field
switch set to a
Microphone
switch set to 12.5 kHz
Frequency
The actual sound level in the coupler when loaded by a Type 4180 microphone is:
= 94.00 + 7.35 + 4.30 = 105.65 dB
L
C
0.00 0.20 0.35
0.00 0.10 0.25
0.00 0.10 0.30
31.5 – 500
0.00
0.00
0.00
0.00
0.00
0.00
+ C + C
field W
1.25 4.00 7.20
0.90 2.80 5.45
1.00 3.15 6.20
Frequency (Hz)
1 k 2 k 4 k
0.00 0.05 0.40
0.05 0.10 0.15
0.00 0.00 0.00
–0.05 –0.05 –0.20
0.00 0.00 0.00
0.00 0.05 0.40
Sound Level
– 4188
6.50 4189, 4190
7.50 4191, 4192, 4193
8 k 12.5 k 16 k
1.60 2.65
0.40 1.50 2.50
0.00 0.70 1.15
–0.05 0.50 0.15
0.75 1.90 2.00
1.60 2.65
switch
–
–