Effect of hematoma-induced changes in auricular hardness, thickness and volume on the propagation components of cartilage conduction hearing: assessments by hearing threshold and ear canal sound pressure

Abstract Cartilage conduction (CC) is a method of perceiving sounds via biological tissues by presenting a transducer to the auricular cartilage. Unlike conventional bone conduction perceived via bony sections of the skull, conduction through light auricular cartilage requires a weak force, resulting in lesser pain. CC is useful in individuals with auricular deformities such as auricular hematoma, in whom, ordinary earphones are unsuitable. However, hematoma-induced changes in the hardness, thickness, and volume of auricular cartilage might affect CC perception. This study investigated the effects of these factors on perception and sound propagation in CC by measuring hearing threshold and ear-canal sound pressure (ECSP) in individuals with normal-ear-morphology and auricular hematoma. The results showed that increased hardness, thickness, and estimated hematoma volume were associated with low ECSP and high hearing thresholds at 250–1000 Hz suggesting that increased auricular mass and greater transducer-to-eardrum distance reduced vibration and/or air-conduction efficiency, potentially impacting CC perception.