D-0100778 Rev C
87
Chapter 8: Routine Maintenance
Biological Calibration Check
The design of the GSI AudioStar Pro audiometer should provide trouble-free
service for a long time period. It is recommended to routinely make and file the
audiogram of one person for the purpose of biologic calibration. This person (or
group of persons) should have a known stable audiometric curve that does not
exceed 25 dB HL at any frequency. This procedure should start when the GSI
AudioStar Pro is first installed and then be continued. Remember that individual
thresholds can shift by as much as 5 dB from day to day; however variations that
exceed this range may point to difficulties which require attention.
Periodic Checks
The routine maintenance checks described below may point to the source of
some instrument problems. If they do not, the instrument should receive technical
service before further use. The checks should be made at periodic intervals, even
if biologic checks reveal no problems.
Earphone and Bone Vibrator Cords
With extended use, all transducer cords tend to fray internally at the connectors.
To evaluate the cord status, turn on the GSI AudioStar Pro. Set the HL to a
comfortably audible level. Place the transducer on your head. Activate both
Interrupt buttons. Bend the cord next to the plug at both ends of each earphone.
Listen for an intermittent signal, abrupt changes in the signal level, or a scratchy
sound that coincides with the flexing of the cord. The presence of any of these
conditions signifies that the cord should be replaced. Repeat this check for all
transducers.
Hum and Noise
Set the GSI AudioStar Pro to Tone test type with the standard earphones selected
and the Channel 1 Interrupt button in the ON mode. Turn the Channel 1 Hearing
Level control from 0 to 60 dB HL. Listen for low frequency hum (60 or 120 Hz)
and any other noise (hiss or low rushing sound) at all attenuator levels through
the earphone. Some audible noise at levels above 70 dB is permissible. If these
noises are detected below 70 dB, the audiometer should be scheduled for
maintenance. Repeat for Channel 2.
Distortion and Frequency Shift
Check for distortion and frequency shift by listening to the GSI AudioStar Pro’s
output through the earphones at each frequency (in the 125 Hz to 12,000 Hz
range) at a loud, but not uncomfortable level (70 to 80 dB HL for normal ears).
Listen also to ensure that the signal frequencies change appropriately when the
Frequency up arrow (>) and down arrow (<) pushbuttons are operated. If
distortion is heard in one earphone but not the other, the chances are high that the
