Effects of direction and rate of ear-canal pressure changes on tympanometric measures.

The effects of the direction (ascending and descending) and rate (12.5, 25.0, and 50.0 daPa/s) of ear-canal pressure changes on three tympanometric measures (peak static admittance, shape, and tympanometric peak pressure) were studied in 24 adults with normal middle-ear transmission systems. Susceptance, conductance, admittance, and phase angle data for the six conditions both at 226 and 678 Hz were obtained using a general purpose computer. Peak static admittance was significantly affected by both the rate and direction of pressure change as evidenced by a decrease in phase angle for ascending and for fast rates of ear-canal pressure change. Tympanometric shape was broader for descending pressure changes with less frequent notching both for descending and for slow rates of pressure change. Finally, the difference in peak pressure for the two directions of pressure change increased with the rate of ear-canal pressure change.