Functional-Dimension Offset Effects on Physical-Dimension Comfort Perception

Wearing comfort in intrusive external-ear wearables is shaped by the dynamic interaction between functional performance and physical sensation rather than by physical factors alone. Focusing on the auricle-external acoustic meatus (EAM) transitional structure, this chapter employs the Tragus Expansion Index (TEI) to standardize structural expansion and to examine its relationship with comfort perception. Experimental results reveal a bell-shaped exposure-response relationship between TEI and comfort ratings, which is effectively characterized using a Gaussian peak fitting model with high statistical reliability. Analysis indicates a staged perception mechanism across increasing TEI levels. In the comfort-increasing interval, functional-dimension perception, such as stability and wearing assurance, dominates and can fully offset emerging physical discomfort. In the subsequent comfort-decreasing interval, functional and physical dimensions interact, while at higher expansion levels physical discomfort becomes the primary determinant of overall comfort. Discomfort perception is also shown to propagate from the tragus to adjacent auricular and periauricular regions along cutaneous nerve pathways, highlighting its systemic nature. Although sex-related differences diminish after anthropometric adjustment, female participants demonstrate lower discomfort thresholds, which are critical for universal design considerations. Based on quantified comfort thresholds and exposure limits, the study provides ergonomic guidance for balancing functional stability and physical comfort, and advances understanding of perceptual offset effects in the design of intrusive ear-related wearable devices.