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Publication Date


First Advisor

Susan E. Voss

Document Type

Honors Project

Degree Name

Bachelor of Science




Wideband acoustic immittance measurements, Reflectance, Absorbance, Impedance, Middle ear, Time domain reflectance, Broadband communication systems, Absorbance scale (Spectroscopy), Acoustic impedance, Time-domain reflectometry


The research has a particular focus on wideband acoustic immittance (WAI) measurements, a family of power-based and impedance-based acoustic measurements that are under development as a diagnostic tool for human hearing. Results from the WAI measurements can not only provide diagnostic information on the tympanic membrane and middle ear via a non-invasive method but also help determine ear-canal geometry, which has a range of practical and theoretical implications. This study has three major parts: 1) determine normative WAI measurements from human subjects; 2) develop and validate a quantity referred as "time-domain reflectance" (TDR) calculation method on well-defined acoustic horns based on the WAI measurements on acoustic horns; and 3) apply TDR calculation to human subjects and calculate ear-canal areas from TDR to compare with measured areas.

Work proceeded at Smith College involved the measurement of WAI on normal ears from 172 subjects with the two most common instruments (Titan, HearID), an experimental instrument (ER10x), and control of age, gender, and race of subjects. To conduct theoretical and experimental work on acoustic horns, I physically built acoustic horns models by generating their CAD files with known cross-section area functions using SolidWorks and a 3D printer in Center for Design and Fabrication in Smith. Subsequently, WAI measurements were made on the acoustic horns. MATLAB scripts adopted from Dr. Stephen Neely were studied and modified to try to calculate the TDR. The TDR calculation method was verified by the consistency between the theory and experimental results on acoustic horns.

Then, this TDR calculation method was applied to human ears. The ear-canal cross-section functions for each valid subject were generated based on the TDR results. At last, the TDR-based predicted ear-canal entrance areas were compared to the measured entrance areas, and the predicted areas were systematically lower than the measured ones. Future work will be needed to identify how the theory can be modified to better represent this system.




210 pages : color illustrations. Includes bibliographical references (pages 60-63)