GSi TYMPSTAR PRO, User Manual

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The probe contains one microphone, two receivers and an air channel. One of the
receivers is used for probe tone signal. The second receiver is used for the
acoustic reflex stimulus signal. The microphone measures the response. The air
channel is connected to the pump system which makes it possible to supply the
eardrum with air pressure. Acoustic energy, commonly referred to as the probe
tone, is introduced into a hermetically sealed ear canal. The decibel level of this
tone is monitored via a microphone with measurements taken at fixed time
intervals.
As pressure within the ear canal is varied, the eardrum is subjected to varying
degrees of stress which alters mobility of the eardrum. Maximum mobility will
occur when the pressure on both sides of the eardrum are equal. Changes in
mobility of the eardrum tend to produce changes in the probe tone level within
the ear canal. Probe tone decibel level changes indicate the amount of sound energy
entering the middle ear.
The acoustic reflex consists of a response by one or more middle-ear muscles to
suprathreshold acoustic stimulation of the auditory pathway. To elicit an
acoustic reflex, an acoustic stimulus (pure-tone, noise, or click) is presented to the
ear canal by a probe or earphone.
Contraction of the stapedius muscle and/or
the tensor tympani stiffens the eardrum and the ossicular chain; thereby,
decreasing the ease with which sound enters the auditory pathway.