Shape-Structure Characterization of the External Ear

The external ear, consisting of the auricle and the external acoustic meatus (EAM), plays a critical role in sound transmission and serves as an essential interface for numerous ear-related devices, including hearing aids, earphones, and protective equipment. Despite its ergonomic importance, detailed anthropometric characterization of the external ear has historically been limited compared with head-face measurements. This chapter establishes a systematic framework for external ear shape-structure characterization through measurable variables, anatomical landmarks, and three-dimensional data acquisition. A total of 40 variables is defined, including 18 auricular measurements and 22 EAM measurements, covering linear, angular, circumference, and area parameters. These variables capture key morphological features such as auricular contour, conchal geometry, protrusion, canal entrance, bends, depth, and spatial orientation. Data were collected from 1120 participants across eight Chinese cities using non-contact 3D scanning combined with impression molding for the EAM. Statistical analyses, including ANOVA, correlation tests, and factor analysis, reveal significant effects of age, sex, and bilateral differences on external ear morphology. The proposed characterization provides an ergonomic foundation for designing ear-worn products, improving comfort thresholds, and enabling future individualized fitting applications.