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LI0063 – Revision 29 May 2015
Calibration
Periodical Calibration
All measurement microphones need periodical calibration for obtaining reliable results. How often
depends on your requirements and on the environment the microphone sets are exposed to. We
recommend at least one calibration per year. G.R.A.S. offers equipment for calibration as well as
calibration services. There are 2 types of calibration:
•
Sensitivity (performed with the microphone grid on)
•
Frequency response
How to Perform Sensitivity Calibration
Sensitivity calibration requires that the microphone set is detached, the grid mounted, and placed
in the appropriate calibration adapter. The following items are needed:
•
A pistonphone (The G.R.A.S. 42AP is recommended)
•
One of the following pistonphone calibration adapters contained in the OP0023 Kit for
Sensitivity Calibration of Flush-mount Microphone Sets:
– 1/2” flush-mount microphone set: RA0221
– 1/4” flush-mount microphone set : RA0228
– 1/8” flush-mount microphone set: RA0278
No correction factor is required with any of these adapters.
For further instructions, see the manual for the G.R.A.S. OP0023 Kit for Sensitivity Calibration of
Flush-mount microphones and the manual for your pistonphone.
How to Perform Frequency Calibration
Frequency calibration requires that the microphone set is detached and that the grid is removed.
The G.R.A.S. OP0024 Kit for Frequency Calibration of Flush-mount Microphone Sets and the
G.R.A.S. 14AA Electrostatic Actuator Amplifier are required.
Frequency calibration is performed as described in the manuals for
•
G.R.A.S. OP0024 Kit for Frequency Calibration of Flush- mount Microphone Sets
•
G.R.A.S. 14AA Electrostatic Actuator Amplifier
•
G.R.A.S. 90CA Microphone Calibration System
The only difference is that other actuator and adapters are used. See page 7 for a list of the
contents of the G.R.A.S. OP0024.
