Operating Instructions MA 50
Geba_MA50_Fe_11a.doc
11 851 406/2 11/11
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If the signal was recognized by the patient as not uncomfortable
increase the level and proceed as described before.
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If the signal was uncomfortable for the
patient note the values.
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Proceed accordingly with other test
frequencies.
For hygienic reasons it is important to clean
the ear cushions of the headphone (see
chapter 8).
4.3 Bone Conduction (BC) Testing
Bone conduction, i.e. the transmission of
sound waves through the skull directly to the
inner ear conways information about the
function of the inner ear. For a neural hearing
loss the values of air conduction (chapter 4.1) and bone conduction are the
same. In this case a hearing loss of the middle ear can be eliminated.
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Place the bone conduction receiver so that the flat, circular side of the
transducer Y is placed on the mastoid, at the noticeable ledge of the cranial
bone behind the auricle (see picture 14). The other side of the headband is
placed in front of the opposite ear.
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Set the receiver selector
to BC.
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Perform the test the same way as for air conduction (see 4.1). Enter the
measurements for all frequencies on the form, connect all points with dotted
lines marked on the audiogram form as follows: > = right and < = left.
For hygienic reasons it is important to clean the bone conductor (see chapter
8).
4.4 Masking of the opposite ear
The basics of masking are explained below. To begin testing immediately,
please go directly to 4.4.3 Manual masking.
4.4.1 Crossover:
When measuring a pure tone audiogram you assume that the measured
hearing threshold is correct. But if you recognize that sound is also
transmitted through bone conduction over the entire skull it is probable that
the opposite ear has also received sound. This is called “crossover”.
Crossover can also occur when measuring air conduction because a small
amount of air conducted sound is received by the skull and transmitted by
bone. Whether the crossover signal can hear by the opposite ear depends on
its inner ear function.
Picture 14 correct seating
of the bone conductor
Summary of Contents for MA 50
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