Welch Allyn MICROTYMP 4 User Manual page 16

Welch Allyn MicroTymp® 4 Tympanometer User Manual
different frequency is presented (the reflex stimulus). The sound pressure level (SPL) of this
stimulus is increased in steps until the middle ear muscles respond causing the tympanic
membrane to become stiffer, or a preset maximum SPL 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 acoustic 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 MicroTymp 4 can measure an acoustic reflex at any combination of 500Hz, 1000Hz, 2000Hz
and 4000Hz. The maximum level for the reflex stimulus may be preset, along with the step size
in dB between the three preceding lower levels of stimulus.
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