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D00073611 Siemens SD 270 Service Manual
warble procedure as the instrument will already be in the appropriate
display mode for this operation.
5.
Free-field Warble Tones Calibration
5.1
Entering Free Field Calibration Mode
Press OPTIONS and then the NEXT key to move through the menu
items and access the ‘Set freefield levels’ screen. Press the YES key.
Press QUIT and you are now presented with the freefield calibration
screen for Warble tones.
The audiometer will now output at 70dBHL from the Left channel.
As reference for the calibration of warble tone sound pressure levels, the
values from ISO 389-7, Table 1 are used (binaural, on-axis).
Freq
[Hz]
125
250
500
750
1000 1500 2000 3000 4000 6000 8000
dB
SPL
92
81
74
72
72
70.5 68.5 64
63.5 72.5 81.5
If a calibration of the speech channel has already been carried out:
Adjust the calibration level for the 1kHz, Left channel using the SIGNAL
control to reach the SPL level specified above as measured by the SLM
If a calibration of the speech channel is not required:
The output of the external amplifier should be set in order to achieve the
level specified above at 1000Hz (i.e. 72dBSPL) as measured by the SLM
with the audiometer set to 0dB compensation. The amplifier’s level control
should
not
then be changed.
When 1kHz, Left channel has been calibrated:
At every other frequency the adjustment should then be made as follows
to give the above values as measured by the SLM.
Change frequency using the Hz keys and then adjust the
calibration level for the new frequency using the SIGNAL control to
reach the correct level as measured by the SLM