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Page 36
D00073611 Siemens SD 270 Service Manual
If necessary it is possible to switch between speech (competing noise)
and warble calibration modes by pressing SPEECH and WARBLE
respectively
To store the levels and leave Free-field calibration mode, press the
STORE key
6.
Free-field Live Speech Calibration
Note: as stated in Appendix 1 of this operating manual, users should be
aware that there is a growing body of professional opinion that Live Voice
speech audiometry is generally not recommended. Exceptional skill and
concentration are required to achieve accurate and consistent levels.
Connect a microphone to the MIC1 input on the audiometer
Press SPEECH and use Softkey 1 to ensure that ‘MIC’ is displayed in
capitals (indicating that the external microphone is selected)
The input signal is adjusted in 1dB steps with the MASK rotary control
Input signal adjustment should be made to adjust for the operator’s
voice to peak at the 0dB point on the LEVEL dB bar graph
If recorded speech has been calibrated no further action is necessary
If recorded speech has not been calibrated, the volume control of the
amplifier should be adjusted so that the SLM reads 90dBSPL at the
listening point with a 70dBHL setting on the instrument; note that this
is an approximate setting only, as it is not possible to produce a true
calibration signal in live speech