Spatial audio through a bone conduction interface

Abstract

Headphones are the standard presentation device for radio communication in the military. Although bone conduction devices possess several advantages over headphones for some military applications, they are generally considered inappropriate for inclusion in a multi-channel system. The current study tested the feasibility of a multi-channel bone conduction system by measuring the localizability of spatialized auditory stimuli presented through a pair of bone conduction vibrators. Listeners localized a Gaussian noise stimulus spatialized with individualized head-related transfer functions (HRTFs). The sounds were presented from eight virtual locations on the horizontal plane (0, +/-45, +/-90, +/-135, and 180 degrees ) through either stereo headphones or a stereo bone conduction system. Localization performance was found to be nearly identical for both audio systems, indicating that bone conduction systems can be effectively used for displaying spatial information.

An Empirical Study of Hear-Through Augmented Reality: Using Bone Conduction to Deliver Spatialized Audio

“…In this study, we opted to use captured spatial audio rather than use HRTFs. While we feel that captured audio should be used for RW sounds, in order to leverage the quality of the sample, we also feel that HRTFs should be used for CG sound, as others have found that localization performance using HRTFs to be indistinguishable comparing headphones to BCH devices [9]. Another conclusion has to do with the frequency response of the BCH unit used in our study.…”

“…This occurs because vibrations from the transducer on one side of the head not only reach the near cochlea, but also the cochlea of the far ear. However, MacDonald et al (2006) showed that the interaural level difference and the interaural time delay of signals displayed using bone conduction are sufficient for users to achieve localization performance similar to standard headphones [9]. The study by MacDonald et al used individualized HRTFs for spatialized headphone and bone-conduction audio, and measured how well four listeners could judge the source of a sound played at one of eight locations equally spaced around the listener in the horizontal plane of the head.…”

“…It is clear from this data that when in doubt, subjects tended to err away from the Center position, and towards the Left or Right extremes. MacDonald et al (2006) refer to this as subjects being able to correctly lateralize the sounds, but not necessarily localize the sounds [9]. Lateralization means subjects knew from which side of the head the sounds came, but had difficulty being more precise than that.…”

“…Table 6 shows the mean relative error for each reference position. As in MacDonald et al [9], we calculate localization error as the angular distance between the perceived and actual (reference) locations in degrees. The relative error shows the direction of the error, with negative numbers indicating errors to the left of the reference tone.…”

Sensory Augmentation through Tissue Conduction

“…Until recently, TC conveyed audio signal but not spatial information, and so the experience was not equivalent (in this respect) to real-world hearing. Latterly, researchers have shown that a considerable of degree of lateralisation, in some case approaching that of normal binaural hearing, is feasible [10][11][12]. Nevertheless, the results lack equivalence in terms of overall spatial performance, significantly lacking spatial attributes such as externalisation, spaciousness, range perception and elevation perception.…”