SM010-3 Siemens SD 270 Operating & Service Manual Page 35
Repeat the above until all frequencies have been calibrated for the
Left channel
To calibrate the Right channel (if required) press the RIGHT key (do
not
change the amplifier’s volume control)
Adjust the calibration for all of the right channel frequencies (including
1000Hz) by using the Hz keys and the SIGNAL control as
described above
To store the levels and leave Free-field calibration mode, press the
STORE key
If required, all calibration levels can be set to a default of zero by
pressing Softkey 1 (‘Zero all’) while in free-field calibration mode
It is possible that, because of the characteristics of the listening room or
test set-up, the calibration levels above cannot be achieved because the
limit of adjustment is reached for one or more frequencies. Re-
arrangement of the listening room may improve the situation, but if not, the
following is a possible solution:
Set all of the frequencies for which calibration can be achieved
For frequencies where this is not possible, adjust each to be a multiple
of 5dBs from the required level
Produce a correction table for each frequency for which calibration
could not be achieved to be applied to the output level of the
audiometer while conducting a test to relate the instrument display to
actual output level from the speakers.
5.2
Calibrating the Competing Noise Channel
This part of the calibration procedure may be omitted if Free-field speech
calibration is not required.
Enter the Free-field calibration mode as described in A2.5.1
Press the SPEECH key and the display will change to indicate the
option to adjust the competing noise calibration level – the legend “Sp
Mask” is used to indicate this
Without changing the setting on the external amplifier use the SIGNAL
control to adjust the level of the competing noise to 90dBSPL as
measured by the SLM using dBA settings.
Calibrate each channel, pressing the RIGHT and LEFT keys to switch
between channels