Effect of occlusion effect by bone-conducted sound on monosyllable articulation*

Bone conduction (BC) technology allows us to hear sounds without having anything blocking our ears and enables hearing even when wearing earplugs. However, optimizing this technology presents challenges, particularly in relation to the occlusion effect (OE), a phenomenon that takes place when the ear canal is occluded, causing low-frequency sounds to seem louder than their original intensity. While some facial regions exhibit greater OE than conventional areas, the impact of OE on speech perception in different facial regions has not been thoroughly investigated. This study explores the relationship between OE and speech perception in various facial regions to inform the functionality of BC technology. We conducted a quantitative analysis of monosyllable articulation in the mastoid process, condylar process, nasal bone, and infraorbital region using both female and male voices to assess OE's impact on speech perception. Our findings reveal that OE improves articulation, facilitating voice communication; however, the extent of articulation enhancement varies depending on the stimulus location and phoneme. By examining OE’s role in speech perception, this research report contributes to the development and use of more effective BC technology applications.