In everyday life, localizing a sound source in free-field entails more than the sole extraction of monaural and binaural auditory cues to define its location in the three-dimensions (azimuth, elevation and distance). In spatial hearing, we also take into account all the available visual information (e.g., cues to sound position, cues to the structure of the environment), and we resolve perceptual ambiguities through active listening behavior, exploring the auditory environment with head or/and body movements. Here we introduce a novel approach to sound localization in 3D named SPHERE (European patent n° WO2017203028A1), which exploits a commercially available Virtual Reality Head-mounted display system with real-time kinematic tracking to combine all of these elements (controlled positioning of a real sound source and recording of participants' responses in 3D, controlled visual stimulations and active listening behavior). We prove that SPHERE allows accurate sampling of the 3D spatial hearing abilities of normal hearing adults, and it allowed detecting and quantifying the contribution of active listening. Specifically, comparing static vs. free head-motion during sound emission we found an improvement of sound localization accuracy and precisions. By combining visual virtual reality, real-time kinematic tracking and real-sound delivery we have achieved a novel approach to the study of spatial hearing, with the potentials to capture real-life behaviors in laboratory conditions. Furthermore, our new approach also paves the way for clinical and industrial applications that will leverage the full potentials of active listening and multisensory stimulation intrinsic to the SPHERE approach for the purpose rehabilitation and product assessment.

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