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Chapter 30 — 1
Chapter 30
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HEARING LOSS
This chapter may be easier to understand if the structure and function of the ear, as outlined
previously in Chapter 9,
is reviewed. All cases of hearing loss should be assessed by a diving
physician.
Divers frequently complain of a sensation of hearing loss which cannot be verified when
hearing tests (pure tone audiometry) are performed. It is likely that currently available
hearing tests, such as speech discrimination, are not sophisticated enough to detect such
subtle alterations in the sensation of hearing.
The
causes
of demonstrable hearing loss fall into two categories:
• Conductive hearing loss –
where there is some impediment to the conduction of
sound vibrations (usually in the external and middle ear)
en route
to the hearing organ.
• Sensorineural (nerve) hearing loss –
where sound vibrations reach the hearing organ
(cochlea) in the inner ear, but the sound is not perceived due to damage of the cochlea or its
nerve.
CONDUCTIVE HEARING LOSS
The likely causes of conductive hearing loss are in the external or internal ear.
External Ear Obstruction
Any obstruction to the outer ear such as wax accumulation, plugs or hoods, outer ear
infections (see Chapter 28) or exostoses (see Chapter 32) can cause this.