Table 4-l:
CALIBRATION REFERENCE THRESHOLDS
Freq
-
(Hz)
125 250 500
750
1000
1500 2000 3000
4000
6000
8000
dB 45.0 25.5 11.5 8.0
7.0 6.5
9.0
10.0
9.5
15.5
13.0
Standard Reference Threshold Levels re: 20
uPa
for
Telephonics
TDH39-P
earphones as measured on the National Bureau of Standards
9-A coupler.
Reference ANSI
S3.6-1989,
IS0 389-1975 Standards.
4.2 CALIBRATION MODE OPERATION
The
Calibration Mode is
used to
perform
the
transducer
calibration.
This
calibration information is used
during
the
Normal
Mode
to determine the correct
attenuator
position to
produce
the required SPL for the selected HL.
The
Calibration
Mode consists of two modes.
The Custom SPL Selection Mode allows the selection of
customized
SPL values
for
alternate
transducers.
The
Transducer
SPL
Calibration
Mode is used to calibrate the sound
pressure
level
(SPL) of each stimulus for each transducer.
4.2
.1
CAL/NORMAL SWITCH
This switch is used to select the operating mode of the
instrument.
The Calibration Mode is entered by setting this
switch to the CAL position while Dip Switch
S1
is in the OFF
position.
The Calibration Mode is exited by setting this switch
to the NORMAL position.
4.2.2 CALIBRATION MODE DIP SWITCHES
(See
"Calibration Mode Dip Switch In-Depth Description" later in
this section.)
These
Dip Switches select various options of
the Calibration
Mode.
They are read to determine the selected options when
the
Calibration Mode is entered.
79
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