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D-0126050 rev 1 -
270+ Operating Manual
3.
PRINCIPLES OF OPERATION
3.1.
OTOSCOPIC EXAMINATION
A suitably-qualified health care professional should perform a thorough otoscopic examination to establish that
the condition of the ear is suitable for the test options selected and that no contraindications are present. The
latter would include obstruction of the external ear canal due to excessive wax and/or hairs, both of which
would need to be removed. This is required to ensure that the pure tone delivered by the earphone is able to
reach the ear drum and is not reflected by cerumen or debris and thereby alter the test result.
3.2.
PRINCIPALS OF PURE TONE AUDIOMETRY
Ideally, hearing tests are conducted in a soundproof room. The purpose of pure tone audiometry is to measure
the patient’s hearing threshold which is then compared to the hearing threshold of an average normal hearing
person. The examination starts with air conduction on the ear with better hearing, or if not specified differently,
on the right ear. The BSA (British Society of Audiology) recommends starting the test at 1000 Hz to then next
measure the higher frequencies. When done with the high frequencies 1000 Hz shall be retested and to then
continue with the lower frequencies. When air conduction is completed, bone conduction is performed.
In cases of unsymmetrical hearing, it might be required to mask the air and bone conduction in order to prevent
hearing the test tone on the opposite ear. This phenomenon is called ‘crossover’ and occurs more often while
testing bone conduction then air conduction.
3.3.
PRINCIPALS OF SPEECH AUDIOMETRY
Speech audiometry has become a strong tool to assess hearing loss. In addition to pure-tone audiometry, the
degree and type of hearing loss can be determined and further information about word recognition and
tolerance to speech stimuli can be identified. Also, speech audiometry is used to fit hearing aids or other
amplifying devices.
3.4.
PRINCIPALS OF FREEFIELD AUDIOMETRY
Speech audiometry is often conducted in a freefield audiometry setup, to evaluate the use and benefit of
hearing aids for the patient.
Summary of Contents for 270+
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