Operating Instructions MI 34 / MI 34 H
GEBAmi34e.11a.docx
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850 232/14 08/11
Figure 10
The middle ear
hearing
nerve
ear canal
middle
ear
bones
ear drum
middle ear
eustachian tube
cochlea
musculus
stapedius
Figure 11 – Principle of impedance measurement
4 How to create a Tympanogram
In the following paragraph we will deal shortly with the principle and the
background of the impedance measurement to create a better
understanding. If you want to begin the measurements immediately just
skip this paragraph and continue reading with
4.3 Preparing the
measurements
.
4.1 The basics of the impedance measurement
The impedance measurement
serves the diagnosis of the
condition of the middle ear and
can therefore not be compared
directly with other audiometrical
tests such as sound or speech
audiometry which serve the
measurement of the hearing.
Furthermore the impedance
measurement is an objective
measuring method which does
not depend on the cooperation
of the test person and can
therefore not be falsified by him.
The two most important impedance measuring methods possible with your
MI 34 are Tympanometry and the measurement of the Stapedius reflex
which is treated in chapter 5. “How to measure the stapedius reflex”.
The impedance measurement
examines the acoustic resistance of the
middle ear. If the eardrum is hit by a
sound a part is absorbed and sent via
the middle ear to the inner ear while
the other part is reflected. The stiffer
the eardrum is the more sound is
reflected and the less sound reaches
the inner ear. In the probe of the
impedance measuring instrument a
small loudspeaker is installed which
emits a sound of low frequency via a
tube
A
(see Figure 11) into the
