AmpliVox Otowave 302, Руководство по эксплуатации

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PRINCIPLES OF OPERATION
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D-0115696-C (OM038)
– Otowave 302 Operating Manual
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 and thereby damage of the hearing organ.
In acoustic reflex testing, the 226Hz tone is used to measure the admittance of the ear, while a short tone at a
different frequency is presented (the reflex stimulus). The level of this stimulus is increased in steps until the
stapedial muscles respond causing the tympanic membrane to become stiffer, or a preset maximum level is
reached. When the change in admittance exceeds a predetermined threshold this constitutes a reflex and the
change in admittance at that level when the stimulus is applied is displayed as a plot against time.
The stapedial reflex is measured at the static ear canal pressure that produces the maximum membrane
admittance, so reflex measurements are taken after the tympanogram is measured when the peak admittance
pressure has been established.
The reflex stimulus may be produced in the ear being measured (ipsilateral mode), the opposite ear
(contralateral mode) or in both ears (ipsilateral mode followed by contralateral mode). For contralateral
stimulation the reflex tone is produced in a separate transducer supplied with the instrument.