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The influence that repeated tympanometric trials have on the aural-acoustic admittance characteristics of the middle-ear transmission system was studied in 24 young adults. The 226-Hz and 678-Hz data were generated by concurrently digitizing the conductance and admittance tympanograms at 25 daPa/s for both ascending and descending pressure directions. Ten successive trials for each frequency and direction of pressure change were made. Changes in admittance corrected for ear canal volume across the 10 tympanometrie trials were computed. The results demonstrated that generally admittance increases as the number of trials increases. For many subjects, the complexity of the tympanometric configuration also increases across trials. The results from eight subjects with single-peaked 678-Hz tympanograms were compared with the results from eight subjects with notched 678-Hz tympanograms to explain the mean decrease in susceptance across tympanometric trials. Finally, the pressure peak locations of the conductance, susceptance, and admittance tympanograms were evaluated and are discussed. The effects that differences in peak pressure location have on the computed static admittance values are presented.

Circumaural earphones provide improved coupling when compared with the standard supra-aural audiometric earphone (TDH 39, 49) [Kruger et al., J. Acoust. Soc. Am. 67, S91 (1980); Villchur, ibid. 48, 1387–1396 (1970); Erber, ibid. 44, 555–562 (1968); Shaw, ibid. 39, 471–479 (1966)]. The variability of real-ear responses of the TDH-49 earphone, audiometric circumaural earphones (Villchur-Telephonics Model 566, Beltone Auraldome & Audiocap), a hi-fi circumaural earphone (Sennheiser HD 430) and an insert phone (Knowles BP 1869) was assessed. Probe microphone frequency response measurements in the ear canal were used to evaluate intrasubject and intersubject variability with the above transducers (10Ss: 5♂, 5♀ 5 repetitions/condition: transducer, subject versus experimenter placement) and were referred to either the diffuse field or the tympanic membrane. Real-ear response variability is contrasted with KEMAR response variability [Kruger et al., (1980); Ciechanowski and Cooper, J. Am. Aud. Soc. 2, 88–94 (1976)] and with coupler calibration variability appropriate to the transducer (NBS 9-A coupler, Penn State flat plate coupler, Zwislocki coupler). The nature of the variations in real-ear responses with these supra-aural, circumaural, and insert earphones will be discussed in terms of calibration, probe microphone placement, coupling to the head, and earphone placement. [Work partially supported by AOS.]

Missing data is a common problem for data clustering quality. Most real-life datasets have missing data, which in turn has some effect on clustering tasks. This chapter investigates the appropriate data treatment methods for varying missing data scarcity distributions including gamma, Gaussian, and beta distributions. The analyzed data imputation methods include mean, hot-deck, regression, k-nearest neighbor, expectation maximization, and multiple imputation. To reveal the proper methods to deal with missing data, data mining tasks such as clustering is utilized for evaluation. With the experimental studies, this chapter identifies the correlation between missing data imputation methods and missing data distributions for clustering tasks. The results of the experiments indicated that expectation maximization and k-nearest neighbor methods provide best results for varying missing data scarcity distributions.