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Publication Date

2024-5

First Advisor

Susan E. Voss

Second Advisor

Stephen Neely

Third Advisor

Eric Jensen

Document Type

Honors Project

Degree Name

Bachelor of Arts

Department

Engineering

Keywords

ear canal geometry, ear canal acoustics, Wideband Acoustic Intermittence measures, 3D reconstruction from CT scans

Abstract

Wideband Acoustic Immittance (WAI) measurement is recognized as an objective, noninvasive diagnostic tool for middle-ear pathologies causing conductive hearing losses. Power absorbance (absorbance) in the WAI family requires calculating with the ear-canal cross-sectional area at the measurement location. Traditionally, researchers and FDA-approved WAI instruments, such as Mimosa’s Hear-ID, have relied on the simplifying assumption that the ear canal is a uniformly cylindrical structure with a constant cross-sectional area. This assumption overlooks the complex, variable nature of real ear canal geometry. Therefore, the objective of this work is to investigate the effects of varying cross-sectional areas and different probe locations on normative adult WAI measurements. In this thesis work, an experimental platform is developed to facilitate WAI measurements on subject-specific, 3D-printed ear canal models derived from high-resolution CT scans, and detailed procedures for conducting leak-free absorbance measurements with minimized intrasubject variability are elaborated. Ear canals from eight subjects aged 40 to 50 were 3D printed and coupled to a 3D-printed artificial middle ear for absorbance measurements using a Hear-ID probe. Results show: (1) Absorbance depends on probe location in some canals, especially above 2000 Hz, and the effect of probe position on absorbance might rely on a combination of how quickly the area changes along the canal and how much the canal curves; and (2) variations in ear-canal cross-sectional area become systematically more significant as the canal area increases beyond the assumed 44 mm2. Larger canal areas lead to lower absorbance below about 3000 Hz.

Rights

©2024 Jingxin Jessica Feng. Access limited to the Smith College community and other researchers while on campus. Smith College community members also may access from off-campus using a Smith College log-in. Other off-campus researchers may request a copy through Interlibrary Loan for personal use.

Language

English

Comments

129 pages : color illustrations. Includes bibliographical references (pages 88-92).

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