Free-Field Live Speech Calibration - Siemens SD 270 Operating Manual

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.
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