Effects of Bone Vibrator Position on Auditory Spatial Perception Tasks

Objective: This study assessed listeners' ability to localize spatially differentiated virtual audio signals delivered by bone conduction (BC) vibrators and circumaural air conduction (AC) headphones. Background: Although the skull offers little intracranial sound wave attenuation, previous studies have demonstrated listeners' ability to localize auditory signals delivered by a pair of BC vibrators coupled to the mandibular condyle bones. The current study extended this research to other BC vibrator locations on the skull. Method: Each participant listened to virtual audio signals originating from 16 different horizontal locations using circumaural headphones or BC vibrators placed in front of, above, or behind the listener's ears. The listener's task was to indicate the signal's perceived direction of origin. Results: Localization accuracy with the BC front and BC top positions was comparable to that with the headphones, but responses for the BC back position were less accurate than both the headphones and BC front position. Conclusion: This study supports the conclusion of previous studies that listeners can localize virtual 3D signals equally well using AC and BC transducers. Based on these results, it is apparent that BC devices could be substituted for AC headphones with little to no localization performance degradation. Application: BC headphones can be used when spatial auditory information needs to be delivered without occluding the ears. Although vibrator placement in front of the ears appears optimal from the localization standpoint, the top or back position may be acceptable from an operational standpoint or if the BC system is integrated into headgear.