Sweep-Frequency Tympanometry: Its Development and Diagnostic Value

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Abstract
This reports a newly developed tympanometric system using a sweep-frequency probe tone. For a sweep-frequency tone ranging from 220 to 2 000 Hz, measurements of sound pressure (P) and phase (Θ) were performed at ear canal pressures of 0 and -200 mm H20. The results were expressed as a sound pressure curve (P0-P-200 m decibels), a phase curve (Θ0-Θ-200 in degrees) and a polar curve (P0-P-200, Θ0-Θ-200) against probe tone frequency. Both the frequency at which the sound pressure curve crossed the 0-dB difference line and the peak frequency of the phase curve shifted lower than normal for ossicular disruption and higher than normal for ossicular fixation. Changes in the sound pressure curve and in the phase curve were exaggerated for ossicular disruption and limited for fixation. As the result of these, the polar curve showed an expanded type for disruption and a compressed type for fixation. A review of 220-Hz tympanograms and of the polar curves for 10 patients demonstrated that the latter permitted a better discrimination among ossicular disorders.

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