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Rinne7 test (vide infra). The 512 fork is selected because it is not felt as a vibration and higher frequencies are
heard by air conduction.
A tuning fork should be stroked between the thumb and index finger, gently tapped on the knuckle, or
carefully activated with a rubber reflex hammer. Striking the fork too hard produces overtones as well as too
intense a sound. When tuning forks are used for testing, masking may be necessary. A simple improvised
mask is a sheet of glazed paper rubbed rapidly over the ear to be masked. Forks are particularly useful in the
differentiation between conductive and sensorineural hearing losses.
The Weber test
The 512 Hz fork is used most frequently. A vibrating tuning fork is placed on the mid-line of the forehead. The
incisor teeth can also be used. The examiner asks the patient whether the sound is heard more distinctly in the
right or left ear (lateralization). If a conductive deafness is present, the tone will be heard more distinctly in the
deafer ear. If one ear suffers from a sensorineural type of impairment, the tone will be heard by bone
conduction in the normal ear and not in the nerve-deafened ear.
The Rinne test
This test compares air and bone conduction and determines whether bone conduction is dominant, indicating
a conductive-type deafness, or decreased, indicating a sensorineural-type deafness. The hilt of a 512 Hz
vibrating tuning fork is first pressed against the mastoid bone behind the ear. When the applicant indicates that
it is no longer audible by bone conduction (record the time in seconds) the fork is instantly removed and the
vibrating tines held directly in front of the open ear canal. If it is still audible, wait until it is no longer heard,
and then record the time. The normal ear hears a tuning fork about twice as long by air conduction as by bone
conduction. If the fork is heard by air conduction after it has ceased to be audible by bone conduction, the test
is said to indicate a Positive Rinne. If the fork is audible for a shorter period by air conduction than by bone
conduction, the test result is termed a Negative Rinne. The results should be recorded in actual time heard - for
instance, air conduction 62 seconds; bone conduction 30 seconds.
MALINGERING
Young applicants rarely feign deafness. They are more likely to claim much better hearing than they actually
have. Older air crew and individuals exposed to aircraft noise will at times claim hearing loss. They rarely
claim bilateral loss. Usually they insist that they have total loss of hearing on one side. Several tests have been
devised to help detect the malingerer. The outstanding findings are the inconsistencies. Cases of malingering
and psychogenic deafness should be referred to the specialist.
The Lombard test8
This test to detect malingering depends upon the reflexive increase in loudness of the voice of a speaker with
normal hearing in the presence of loud background noise or masking sounds. The applicant is given easy
reading material and requested to read out loud and to continue no matter what happens. A Barany
noisemaker9 is then placed next to the supposedly good ear of the applicant while he continues to read. A test
7 After Friedrich Heinrich Rinne, German otologist (1819-1868)
8 After Etienne Lombard, French physician (1868-1920)
9 Barany noisemaker: a noise-producing device like a small alarm clock with a button to be inserted into the ear canal
of the patient. After Robert Bárány, Austrian-Hungarian otologist and Nobel laureate (1876-1936)
ICAO Preliminary Unedited Version — October 2008 III-12-15
subject who is truly deaf in the other ear will automatically raise the intensity of his voice as he continues to
read, but the malingerer will continue to read in an even or very slightly elevated tone.
The method of delayed speech auditory feedback is, however, better as it makes it impossible for a malingerer
to speak without stuttering.
AUDIOMETRY
Quantitative measurements of hearing are made using the pure-tone audiometer which produces pure tones
that can be varied according to frequency and intensity. Plotting the intensity against the frequency provides
an audiogram.
Fig. 12-3: Normal audiogram
= right ear; × = left ear; the green line indicates the ICAO hearing requirements
A number of frequencies in the range 125 Hz to 8 000 Hz are tested by presenting a tone loud enough for the
applicant to hear distinctly, and then the threshold level for each frequency is determined. The examinee
signals by finger signs or by pressing a button when a tone is heard and when it is no longer heard.
The zero (0) reference level of a clinical audiometer refers to that sound intensity which can just be detected
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Manual of Civil Aviation Medicine 2(80)
