AmpliVox Otowave 102-C, Руководство по эксплуатации

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PRINCIPLES OF OPERATION
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D-0014930-A
– Otowave 102-C 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 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.
3.2. PRINCIPALS OF ADMITTANCE MEASUREMENT
The Otowave 102-C measures the admittance of the tympanic membrane and middle ear by playing a
continuous tone into the ear canal at 226 Hz. The level of this tone is calibrated to give 85 dB SPL (226 Hz)
into a 2 ml cavity. The sound level this produces in the ear canal is measured using a microphone and the
admittance calculated from the result.
In line with normal audiometric practice admittance is displayed as an equivalent volume of air in ml (for 226
Hz). The residual ear canal volume between the probe and the tympanic membrane is always displayed in ml.
3.3. TYMPANOGRAM
Tympanometry is part of the objective impedance test and provides information about the middle ear mobility
and pressure in the middle ear system.
To record the tympanogram, the admittance is measured while the air
pressure in the ear canal is varied from +200 daPa to -400 daPa by means
of a small pump. The admittance peaks when the air pressure is the same
on both sides of the tympanic membrane. The change of admittance with
pressure is displayed graphically.
3.4. ACOUSTIC REFLEX MEASUREMENT
Using the same principle as in tympanometry measures, it is also possible to establish whether an acoustical
reflex is present. The acoustic reflex is caused by the contraction of the stapedial muscle as a response to
high-intensity stimulation of the ear. The acoustic reflex is also a natural protection of the inner ear from too
high sound pressure levels which can cause damage to the hearing organ.