Occlusion effects by bone-conducted sound to the facial parts assessed by hearing threshold and ear canal sound pressure

Bone conduction (BC) is used in devices such as hearing aids and earphones. Audio devices using BC on the face have been developed; however, limited research has addressed the perception of BC sounds on the face. BC also entails an occlusion effect (OE), wherein the loudness of low-frequency sounds is enhanced when the ear canal is occluded. We evaluated the characteristics of OE by measuring hearing thresholds and ear canal sound pressure (ECSP) during BC stimulation of several facial parts. We compared them with those of conventionally used parts. OE, the difference in hearing thresholds between the open and occluded ears, was equal to or larger than that of conventionally used parts. The difference in ECSP was smaller than that in OE, indicating that BC components transmitted to the middle and inner ears affected OE in these facial parts. The complicated structure of the face may have affected the results.