Free Field Microphone Calibration
The sound pressure unit of a calibrated primary standard microphone is transferred to a tested microphone by a substitute procedure.
The technical measuring process is the comparison between two sound-pressure-proportional microphone voltages at constant sound pressure, using the substitute voltage procedure.
Standard and tested microphone are both exposed to the same sound pressure level ( 84 dB, sine with f= const. ) in an approximate free sound field.
Reference conditions are:
Temperature 23,0 ºC, atmospheric pressure 101,3 kPa and relative humidity 50%.
The temperature and humidity of the low reflection chamber used for free field calibration is stabilized to reference environmental conditions.
Measurement uncertainties for single frequency ranges in dB (re 1 V/Pa)
Frequency range in Hz | Measurement uncertainty in dB |
25 - 80 | 0,4 |
100 - 5.000 | 0,2 |
6.300 - 10.000 | 0,3 |
12.500 - 20.000 | 0,4 |