PRINCIPLES OF OPERATION
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OTOWAVE 302+ INSTRUCTION FOR USE
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 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 ADMITTANCE MEASUREMENT
The Otowave 302+ measures the admittance of the tympanic membrane and middle ear by playing a continuous tone
into the ear canal at either 226 Hz or 1000 Hz. The level of this tone is calibrated to give 85 dB SPL (226 Hz) or 79 dB SPL
(1000 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) or
m
mho/mƱ (for 1000 Hz). The residual ear canal volume between the probe and the tympanic membrane is always
displayed in ml; when using a 1000 Hz probe tone the measured value in mmho is converted to ml using a conversion
factor of 226/1000.
3.3.
TYMPANOGRAM
Tympanometry is part of the objective impedance test battery 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.
