166
Quality checks
CHAPTER SEVENTEEN
Quality checks
17.3
Cavity test
Due to mechanical or electrical failure or a faulty probe, the system may
itself produce signals during a test that have similar characteristics to an
OAE response. The test cavity will not produce any OAE signal so any
signal produced in the cavity is the result of a fault.
By performing an OAE test in a cavity rather than an ear it is possible
to determine whether signal responses recorded in the ear are being
generated by a fault.
Follow the instructions in
Probe test
for inserting the probe into the test
cavity. Start a test on the Otoport as you would for an ordinary ear (see
chapter
7
OAE test selection
).
Follow the
Checkfit
and
Test
screen sequences until the test stops. In a
cavity the Checkfit screen should indicate a large cavity volume.
If the result
Stopped Too Soon
,
Too Noisy
or
Poor Probe Fit
is achieved,
retest checking that the probe ear piece is firmly inserted into the test cavity
and that the noise conditions within the room are acceptable for a test to be
conducted. Continue to retest until a
No Valid OAE
result is given.
At the end of the test:
1. Use the arrow keys to view the
data table
and check that the
noise
values are below -5 in all bands.
2. Use the arrows again to view the
Circles
screen and check that none of
the circles contains a tick.
If either of these conditions is not met, save and retest. Make sure the
earpiece has been firmly pressed into the test cavity.
Condition 1 will only be achieved with low environmental noise levels. If
this is not achieved, containue to repeat the test in a quiet environment.
Electromagnetic interference is an ‘invisible’ source of noise, so if there are
persistent problems and other hardware issues have been eliminated, try to
move to another location to perform the tests.
If condition 2 is NOT met during a repeat measurement, then check the
top of the test cavity ensure that it is securely attached to the clear plastic
part of the test cavity. If the resources are available repeat the test with
a different test cavity and then with a different probe. This will identify
which component is responsible for the problem. Contact your dealer or
Otodynamics for further advice.