6
D-0116493-B (OM015)
– PC850 Operating Manual
2.
PRINCIPLES OF OPERATION
2.1.
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 probe tone delivered by the probe are able to
reach the ear drum and are not reflected by cerumen or debris and thereby alter the test result.
2.2.
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 done with the air conduction, the bone conduction is being
assessed.
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.
2.3.
AUDIOMETRY PREPARATION
Refer to the various audiometric standards and other relevant publications for guidance on audiometric testing.
Ambient Conditions
Audiometric testing should always be performed in quiet conditions (e.g. a quiet room or an acoustic booth).
The optional Audiocups can provide an additional level of isolation from ambient noise. For further
explanation on permissible ambient noise levels, please refer to the audiometry standard ISO 6189.
Test System Arrangement
The schematic diagram below shows a typical example of the use of audiometric test equipment. The
audiometer is located on the desk of a seated operator as shown.
Operator
PC850
Audiometer
Computer (e.g. Tablet/Laptop)
Patient, wearing headset
Headset lead
Response switch & lead
