Effects of Variations in the Tragus Expansion Angle on Users’ Comfort for In-ear Wearables

Tragus expansion angle (TEA) is an angular variable that quantifies the degree of outward expansion of the tragus cartilage induced by in-ear wearables worn in the human ear. However, the TEA cannot be measured directly, and the mechanism that explains how expansion variations affect users’ comfort experience is not well understood. The purpose of this study was to establish a quantitative relationship between variations in the tragus expansion angle and users’ comfort experience. TEA was measured on 400 healthy participants and normalized using a measuring device (ATMC prototype) and Tragus Expansion Index (TEI). Our results show that the comfort range across variations in TEA was similar for both sexes, yet compared to females, males could tolerate larger variations both in TEA and TEI. A quantitative relationship was established using TEI values, (dis)comfort ratings and GaussAmp function, which can be employed for ergonomic design purposes.