Biological
Listening Checks
The rationale for conducting
biological listening checks is to ensure the proper
functioning of the clinic equipment. These checks
should be performed daily or just prior to use, using an
otologically normal individual in a sufficiently quiet
room.
It is also recommended to routinely
make and file the audiogram of one person who will be
available for a Biological Calibration Check. This
person should have a known stable audiometric curve that
does not exceed 25 dB HL at any frequency. This
procedure should be done on a regular basis.
Remember than individual thresholds can shift by as much
as 5 dB from day to tay, however variations that edxceed
this range may point to equipment difficulties which
require attention.
The current standard for biological
listening checks as outlined by the Canadian Safety
Association (CSA) is CAN3-Z107.4-M86.
Routine maintenance checks may point
to the source of error, and cure for some instrument
problems. If they do not, the instruments should
receive technical service before further use. The
checks should be made at periodic intervals, even if
biologic checks reveal no problems.
* the following information
on routine summary was provided to me by EMI Canada and
their experienced calibration staff
Earphone
and bone vibrator cords, microphone cables
Hum
and Noise
Distortion
and frequency shift
Speech
level checks
Internal
controls check
Masking
level check
Talk
forward check
Summary of biological listening
check procedure:
-
Clean
and examine the audiometer and accessories
-
Ensure
that all switch knobs are secure and indictors
function correctly
-
Ensure
that the patients signal system (response switch), if
supplied, operates correctly.
-
Check
tension of headset band.
-
Switch
on equipment and leave on for the recommended warm-up
time.
-
Check
output at a high input (e.g. hearing level of 60 dB)
at all frequencies used, for both earphones, listen
for proper functioning, absence of distortion, freedom
from interrupter clicks, etc.
-
Compare
the current hearing threshold levels of one
otologically normal subject (who may be the
technician) with his/her previously recorded baseline
audiogram
-
Listen
at low levels.
-
Ensure
that the attenuator(s) does attenuate over the full
range.
-
Ensure
that the interrupter keys operate silently and that no
noise radiated from the instrument is audible at the
subjects position.
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