Casella 620 Series - Sound Calibrators - Level Corrections

620 Series
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Sound Calibrators – Level Corrections
Sound level calibrators apply sound pressure to a microphone in a closed cavity. The response of a
microphone in a free field at 1kHz will be slightly different to that of a pressure field. Also some
calibrators are affected by the volume of the microphone changing the volume of the calibrator
cavity.
The wind screen has an affect on the free field response at 1kHz and this can be compensated for
during calibration.
Calibration corrections for the CEL-251 and CEL-252 Microphones.
Calibrator
Calibration Level
Correction no
Wind Screen
Calibration Level
Correction with
Wind Screen
IEC 60942
Casella CEL-120/1
-0.1dB
0.0dB
Type 1
Casella CEL-120/2
-0.1dB
0.0dB
Type 2
Bruel & Kjear 4231
-0.1dB
0.0dB
Type 1 approved
Cirrus CR:515
-0.1dB
0.0dB
Type 1 approved
Examples
The CEL-62X can be calibrated at a nominal level of 94dB or 114dB dependent on the type of
calibrator used.
If a CEL-120/1 is used and the certified output of the calibrator is 113.98dB, and it is intended to
use the sound level meter without the wind screen, then the calibration level will need to be set to
113.88, rounded to 113.9dB.
Calibrator level 113.98
Correction -0.1
Calibration level = 113.88 rounded to 113.9dB
If a Cirrus CR:515 is used and the certified output of the calibrator is 94.04dB, and it is intended to
use the sound level meter with the wind screen fitted, then the calibration level will need to be set
to 94.04, rounded to 94.0dB
Calibrator level 94.04
Correction 0.0
Calibration level = 94.04 rounded to 94.0dB