FIG. 4.

High-frequency tympanometry (1,400 Hz) with various volumes of silicone oil in the middle ear. Type B tympanograms were more common when using a 1,400-Hz probe tone for tympanometry measurements. At 1,400 Hz, subtle changes in the tympanometry curve width were noticeable even with the first 0.5 mL of added middle-ear fluid. With 0.75 mL of fluid in the middle ear, the curves were noticeably shorter and wider. Type B tympanograms were seen at 1.0 mL of fluid in the middle ear. Across all animals, fluid levels above 1.0 mL resulted in type B tympanograms when using high-frequency probes.