Pulsar Nova® sound level meter user manual
Page 56
Free Field Correction
When calibrating a microphone which is to be used for free field measurements, a small
correction may be necessary to compensate for the difference between the microphone’s
free field response at ‘zero degrees’ or ‘head-on’ incidence and the pressure level
generated by the calibrator.
The correction is typically -0.3dB for ½ inch microphones (making the effective
calibration level 93.7dB).
Calibration corrections are listed below for the Pulsar Instruments plc ½” Capsules and
three microphone capsules commonly used in Calibration Laboratories:
Microphone Correction Values
Microphone Type Calibration Correction Effective Calibration Level
PM1 -0.3dB 93.7dB
PM2 -0.3dB 93.7dB
B&K 4134 0dB 94.0dB
B&K 4180 0dB 94.0dB
B&K 4192 0dB 94.0dB
Example:
An example of the procedure used to calculate the value for an PM1 microphone is
shown below :
Level = 94.0dB + Microphone Correction
Level = 94.0dB + ( -0.3dB)
Level = 93.7dB
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