Externalization of Virtual Sound Sources With Bone and Air Conduction Stimulation

Current research on sound source externalization primarily focuses on air conduction (AC). As bone conduction (BC) technology advances and BC headphones become more common, the perception of externalization for BC-generated virtual sound sources has emerged as an area of significant interest. However, there remains a shortage of relevant research in this domain. The current study investigates the impact of reverberant sound components on the perception of externalization for BC virtual sound sources, both with the ear open (BC-open) and with the ear canals occluded (BC-blocked). To modify the reverberant components of the Binaural Room Impulse Responses (BRIRs), the BRIRs were either truncated or had their reverberation energy scaled. The experimental findings suggest that the perception of externalization does not significantly differ across the three stimulation modalities: AC, BC-open, and BC-blocked. Across both AC and BC transmission modes, the perception of externalization for virtual sound sources was primarily influenced by the reverberation present in the contralateral ear. The results were consistent between the BC-open and BC-blocked conditions, indicating that air radiated sounds from the BC transducer did not impact the results. Regression analyses indicated that under AC stimulation, sound source externalization ratings exhibited strong linear relationships with the Direct-to-Reverberant Energy Ratio (DRR), Frequency-to-Frequency Variability (FFV), and Interaural Coherence (IC). The results suggests that BC transducers provide a similar degree of sound source externalization as AC headphones.