Frequency Calibration of the RA0045/RA0045-S1
This section describes how to perform a frequency calibration using a 40BP ¼” Microphone as
sound source. Fig. 12 shows how to configure the coupler for calibration using the accessories
provided, and Fig. 13 shows how these should be used with:
40BP ¼” Microphone
RA0086 Transmitter Adapter
GR0433
Calibration Adapter
GR0434
Stop Washer
Fig. 12.
Assembled and exploded views of the coupler itemising user-serviceable accessories for individual calibration
The ¼” microphone is used as a high-impedance sound source. The complete set-up is shown in
. The computer in Fig. 14 is capable of concurrently generating and measuring audio frequency
signals. The 14AA Actuator Supply receives a swept tone generated by the computer and sends
this, superimposed on a polarisation voltage of 200 VDC, to the coupler mounted in the jig, also
shown in Fig. 14. The coupler picks up the resulting audio signal and sends this back to the com-
puter which traces out and displays the coupler response. An example of a displayed response is
shown in .
40BP
¼
" Microphone
without protection grid
GR0434
Stop Washer
RA0086
Transmitter
Adapter
The assembled components
are pushed into the coupler
Fig. 13.
Assembled and exploded views showing how the GR0434 is used when calibrating the Ear Simulator. 40BP and
RA0086 are available from G.R.A.S.
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LI0070 – 28 June 2017
