Audio Traveler AA222, Operation Manuals, Page: 28 / 141

AA222 Operation Manual Page 28
4) Repeat the familiarisation procedure. If the difference is 5 dB
or less go to the other ear. If the difference is 10 dB or
higher, repeat the test at further frequencies in the same
order until agreement to 5 dB or less has been obtained.
5) Proceed until both ears have been tested.
The hearing threshold at each frequency and ear shall be
calculated according to the following procedure:

Find the lowest level where the subject responds in at
least 50% of the tone presentation series. This level is
defined as the hearing threshold level.

If the lowest response levels span more than 10 dB
within the same frequency the test is doubtful and should
be repeated, if possible.
Manual or automatic pulses may be used. If manual pulses
are used, they should be at least one second in duration.
Bone Conduction
The purpose of the BC test is to supply the test tone directly to the
inner ear around the middle ear mechanism via the skull to establish
the inner ear hearing threshold.
AC-BC gap:
The difference between the AC threshold and BC threshold, the
so called AC-BC gap, will be the loss of the middle ear. The
middle ear loss is of great diagnostic interest as it may indicate
the need for medical attention.
The bone conductor is placed behind the test ear directly on the
skull where the tone is best heard. Activate "Bone R L" (11) and
the test is performed in the same way as for the air conduction
test.
The output switch is set to Bone and the test is performed in the
same way as for the air conduction test.