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Wideband immittance measures can be useful in analyzing acoustic sound flow through the ear and also have diagnostic potential for the identification of conductive hearing loss as well as causes of conductive hearing loss. To interpret individual measurements, the variability in test–retest data must be described and quantified. Contributors to variability in ear-canal absorbance–based measurements are described in this article. These include assumptions related to methodologies and issues related to the probe fit within the ear and potential acoustic leaks. Evidence suggests that variations in ear-canal cross-sectional area or measurement location are small relative to variability within a population. Data are shown to suggest that the determination of the Thévenin equivalent of the ER-10C probe introduces minimal variability and is independent of the foam ear tip itself. It is suggested that acoustic leaks in the coupling of the ear tip to the ear canal lead to substantial variations and that this issue needs further work in terms of potential criteria to identify an acoustic leak. In addition, test–retest data from the literature are reviewed.

Objectives: The development of acoustic reflectance measurements may lead to noninvasive tests that provide information currently unavailable from standard audiometric testing. One factor limiting the development of these tests is that normal-hearing human ears show substantial intersubject variations. This work examines intersubject variability that results from measurement location within the ear canal, estimates of ear-canal area, and variations in middle-ear cavity volume., Design: Energy reflectance (ER) measurements were made on nine human-cadaver ears to study three variables. (1) ER was measured at multiple ear-canal locations. (2) The ear-canal area at each measurement location was measured and the ER was calculated with the measured area, a constant area, and an acoustically estimated area. (3) The ER was measured with the middle-ear cavity in three conditions: (1) normal, (2) the mastoid widely opened (large air space), and (3) the mastoid closed off at the aditus ad antrum (small air space)., Results: Measurement-location effects are generally largest at frequencies below about 2000 Hz, where in some ears reflectance magnitudes tend to decrease systematically as the measurement location moves away from the tympanic membrane but in other ears the effects seem minimal. Intrasubject variations in reflectance due to changes in either measurement location within the ear canal or differences in the estimate of the ear-canal area are smaller than variations produced by large variations in middle-ear cavity air volume or intersubject differences. At frequencies below 2000 Hz, large increases in cavity volume systematically reduce the ER, with more variable changes above 2000 Hz., Conclusions: ER measurements depend on all variables studied: measurement location, ear-canal cross-sectional area, and middle-ear cavity volume. Variations within an individual ear in either measurement location or ear-canal cross-sectional area result in relatively small effects on the ER, supporting the notion that diagnostic tests (1) need not control for measurement location and (2) can assume a constant ear-canal area across most subjects. Variations in cavity volume produce much larger effects in ER than measurement location or ear-canal area, possibly explaining some of the intersubject variation in ER reported among normal ears.

Objectives: To investigate the tympanometric characteristics of Chinese school-aged children with normal middle ear function., Design: Measurements were made for four tympanometric variables [peak, compensated static acoustic admittance (peak Ytm); equivalent ear canal volume (Vec); tympanometric width (TW); and tympanometric peak pressure] from 278 Chinese children aged between 6 and 15 yrs. Data from the right ear were compared across age groups with those of Chinese young adults and with Western children of comparable ages. Data from the left ear were used to examine specificity using tympanometric screening criteria suggested in the present study., Results: The developmental pattern in tympanometric variables found with the Chinese school-aged children in the study was similar to that found with white children in Western studies. Increasing age was accompanied by an increase in peak Ytm and Vec values, a decrease in TW values, and less negative and less varied tympanometric peak pressure values. The lower limit of peak Ytm 90% range of the Chinese school-aged children in the study was lower and their TW values were wider than those of white children. Age-specific data also suggested that the upper Vec limits of children between 6 and 7 yrs of age differed from those of older children. Racial differences in peak Ytm and TW values were noted, in that the Chinese school-aged children had a lower peak Ytm limit and wider TW values than white children. The use of ASHA 1997 guidelines for identifying ears for referral with respect to Chinese school-aged children may therefore not be highly sensitive and specific. Gender differences noted in peak Ytm and Vec values were too small to be of clinical significance., Conclusions: To increase the accuracy of tympanometry in determining ears to be referred for further assessment, the use of the tympanometric characteristics observed in the Chinese school-aged children in the present study (i.e., peak Ytm lower limit < 0.2 mmhos and Vec upper limit > 1.5 cm3) should be considered in addition to ASHA 1997 tympanometric screening guidelines.

Objective: To obtain tympanometric norms in Southern Chinese young adult population and compare the results with data obtained for a Caucasian population., Design: Ear canal volume (Vea), tympanometric compensated static acoustic admittance (Peak Ytm), tympanometric width (TW) and tympanometric peak pressure (TPP) were obtained on 100 Southern Chinese young adults. Results were compared with findings from Roup et al. (1998). Inter-tester reliability was established., Results: Compared with the results obtained by Roup et al. (1998) on non-Hispanic Caucasian population, Southern Chinese subjects were found to have lower Peak Ytm, wider TW and more positive TPP values. No gender difference was noted for Peak Ytm, TW and TPP values in Chinese subjects. Inter-tester reliability was good., Conclusion: The tympanometric norms obtained in this study are recommended when evaluating middle ear function among Southern Chinese young adults.