The effect of vocal and demographic traits on speech intelligibility over bone conduction

Bone conduction (BC) communication systems provide benefits over air conduction systems but are not in widespread use, partly due to problems with speech intelligibility. Contributing factors like device location and background noise have been explored, but little attention has been paid to the role of individual user differences. Because BC signals travel through an individual's skull and facial tissues, demographic factors such as user age, sex, race, or regional origin may influence sound transmission. Vocal traits such as pitch, spectral tilt, jitter, and shimmer may also play a role. Along with microphone placement and background noise, these factors can affect BC speech intelligibility. Eight diverse talkers were recorded with bone microphones on two different skull locations and in different background noise conditions. Twenty-four diverse listeners listened to these samples over BC and completed Modified Rhyme Tests for speech intelligibility. Forehead bone recordings were more intelligible than condyle recordings. In condyle recordings, female talkers, talkers with high fundamental frequency, and talkers in background noise were understood better, as were communications between talkers and listeners of the same regional origin. Listeners' individual traits had no significant effects. Thoughtful application of this knowledge can help improve BC communication for diverse users.