Bachelor of Science
Susan E. Voss
Middle ear, Absorbance, Reflectance, WAI, Ear canal geometry, Ear canal-Anatomy, Hearing disorders-Measurement
Wideband Acoustic Immittance (WAI) measures are a family of related power-based and impedance-based quantities calculated from pressure measurements made in the ear-canal with a probe transducer. Some WAI measures (e.g. reflectance and absorbance) also require the ear-canal cross-sectional area at the measurement location. WAI has been the subject of active research in the development for an objective, noninvasive diagnostic tool for middle-ear pathologies causing conductive hearing loss. Before WAI measures can become clinically useful, more researches are required still, and this work intends to (1) systematically compare three measurement systems of WAI (Mimosa HearID, Interacoustics Titan and Etymotic ER10X); (2) investigate the effects of gender, race, age and ear-canal area on absorbance; (3) design, test and implement a protocol to digitally measure ear-canal cross-sectional areas from silicone ear molds at the measurement location of the HearID system; (4) and examine the sensitivity of absorbance to the actual measured ear-canal area. We found that the mean absorbance measured with HearID was systematically lower than that measured with Titan and ER10X at frequencies below 1.6 kHz; which is consistent with HearID having a deeper insertion depth than both Titan and ER10X. Among all three devices, we found that younger ears have systematically lower mean absorbance than older ears below 1-3 kHz and higher between 4 and 5 kHz; male ears have systematically higher absorbance than female ears below 700 HZ and lower from 2.5 to 4.6 kHz; Caucasian ears have systematically higher absorbance than Chinese ears from 400 to 800 Hz. We observed a wide range of adult ear-canal areas and found that ear-canal area increases with age and male ear-canals tend to be larger than female ear-canals. We also found that the absorbance was sensitive to the actual measured ear-canal area below 2.5 kHz, and the systematic differences observed between younger and older ears below 3 kHz were fully explained by variations in ear-canal areas. We concluded that using an assumed, predetermined ear-canal area for all ears in calculating reflectance and absorbance is questionable.
Xia, Lu, "The effects of age, gender, race and ear canal area on normative adult wideband acoustic immittance (WAI) measures" (2017). Honors Project, Smith College, Northampton, MA.
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