Anthropometry of external auditory canal by non-contactable measurement

• We use the non-invasive computed tomography technology to measure the geometric shape of external auditory canal.
• The length and width of ear canal openings for men are longer, wider than those for women.
• The difference between the length and width of the ear canal opening is about 40%.
• The circular cross-section shape of the earplugs should be replaced with elliptical cross-section shape for better fitting.

Human ear canals cannot be measured directly with existing general measurement tools. Furthermore, general non-contact optical methods can only conduct simple peripheral measurements of the auricle and cannot obtain the internal ear canal shape-related measurement data. Therefore, this study uses the computed tomography (CT) technology to measure the geometric shape of the ear canal and the shape of the ear canal using a non-invasive method, and to complete the anthropometry of external auditory canal. The results of the study show that the average height and width of ear canal openings, and the average depth of the first bend for men are generally longer, wider and deeper than those for women. In addition, the difference between the height and width of the ear canal opening is about 40% (p < 0.05). Hence, the circular cross-section shape of the earplugs should be replaced with an elliptical cross-section shape during manufacturing for better fitting.