General Operation Of The At235 Tympano-Metry Module; Tympanometry - Interacoustics AT235 Additional Information

AT235 Additional Information
2 General Operation of the AT235 Tympano-
metry Module

2.1 Tympanometry

The default display of tympanometry tests shows graphs for both left and right ear. The following information
is found in the display:
A The label above the graphs indicates which probe tone frequency was used while measuring the
recording that is plotted.
B The normative box which shows where the peak of the audiogram is expected in normal middle ear
functioning. The size of the normative box can be customized in the protocol setup. Be aware that
the placement of the normative box is dependent on the ear canal volume. This means that when
the curves are shown in non-compensated view, the box will only be placed correctly after the ear
canal volume is determined.
C The tympanometry curve(s). The numerical values of the curve should be read from the left Y-axis.
For tympanometry performed at 226 Hz the scaling is in ml. For all other probe frequencies, the unit
at the Y-axis is mmho.
D The equivalent ear canal volume. In automated tympanometry, the acoustic admittance (Y) at the
start pressure is taken as the reference value. In manually performed tympanometry, it takes the
acoustic admittance at the highest recorded pressure as a reference. Be aware that at probe
frequencies other than 226 Hz, the equivalent ear canal volume is read from right Y.
E The table with measurement values. Here you will find:
•
Volume, the equivalent ear canal volume
•
Compliance, the peak compensated static acoustic admittance. When the tympanogram is
shown compensated for the ear canal volume, it is the compliance value at the peak.
•
Pressure, the tympanic peak pressure which is at the point of the curve where the highest
compliance value is detected
•
Gradient, If it is chosen to show gradient as pressure, it gives the tympanogram width at
half the height of the peak compensated static acoustic admittance. If it is chosen to show
gradient as compliance, it gives the average of the two compensated admittance values
which are 50 daPa away from the peak pressure.
If the automated measurement for some reason does not reach the end pressure as set in the
protocol setup, the table will only show the equivalent ear canal volume.
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