Chapter 8: Routine Maintenance
Biological Calibration Check
The design of the GSI Pello audiometer should provide trouble-free service for a
long time period. It is recommended to routinely record 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 Pello 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 Pello. 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 Pello 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 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 earphones are at fault