Immittance audiometry. Normative data at 220 and 660 Hz.

Normative immittance data for normal ears were collected at 220 and 660 Hz probe tone frequencies. The experimental set-up enabled conversion of simultaneously recorded susceptance and conductance data to resistance, reactance, admittance and phase angle tympanograms. Special attention was given to the subtraction of the ear canal admittance and to the pump speed. This paper demonstrates first the frequent occurrence (43.2%) of W-shaped tympanograms at 660 Hz probe tone in healthy ears. This percentage is not influenced by age, sex or pump direction. Normative data of the central extremum of the tympanogram are reported only for those immittance components in which W-notching does not occur. The wide variance of measurements in the population precludes the creation of subcategories. The intra-individual variation is much smaller and the authors advocate to use the value of the contralateral healthy ear as a reference.