Morphological differences affect speech transmission over bone conduction

In bone conduction (BC), acoustic signals travel through an individual's bones and soft tissues rather than travelling through the air. While bone conduction hearing and communication are important in everyday life, nature, and technology, little is known about how individual differences affect the transmission of bone-conducted sound. Individuals differ in the sizes, shapes, and proportions of their craniofacial bones, leading to potentially different bone-conducted sound transmission effects in different individuals. Individual differences may influence the audibility and quality of bone-conducted sound, and this was studied using speech intelligibility as an assessment criterion for bone-conducted sound transmission. Thirty-two human participants were first subjected to a series of anthropometric craniofacial measurements. Eight morphologically diverse talkers were recorded with bone microphones placed at different skull locations, and 24 morphologically diverse listeners listened to these samples over bone conduction headphones. Modified Rhyme Test results suggest that skull morphology influences BC speech intelligibility and does so differently at different skull locations. Understanding morphological effects can improve bone conduction sound transmission models and may help to enhance BC technology for a diverse user population.