Binaural signal synthesis is typically formulated as forward modelling using head-related transfer functions (HRTFs). We explore an inverse auditory modelling perspective in which binaural ear signals are estimated directly from a source signal and its azimuth. We present a lightweight complex-valued neural network that predicts frequency-domain binaural filters from the input source spectrum and azimuthal direction, which are then applied to synthesize binaural signals. Controlled experiments evaluate how excitation bandwidth and angular sampling density affect reconstruction and generalization. Results show accurate spectral reconstruction and interpolation to unseen source directions even when training uses sparse angular grids, while bandwidth strongly influences problem conditioning and error behaviour. This work focuses on characterizing compact signal-conditioned inverse models as efficient components for binaural signal generation.
Single-sided deafness (SSD) reduces access to binaural cues and can make spatial-audio localization difficult in virtual reality (VR). This study investigated short-term localization training under simulated SSD in a VR task using generic, non-individualized head-related transfer function (HRTF) rendering with head-movement-contingent auditory updating, and examined whether an enhanced HRTF could improve performance by emphasizing monaurally available spectral cues at the better-hearing ear. The rationale was that, although directional judgment in normal binaural listening depends strongly on interaural differences, monaural listening must rely more heavily on direction-dependent spectral characteristics that remain available at the better-hearing ear. Twenty normal-hearing participants performed a 13-source horizontal-plane localization task using a VR headset and headphones under simulated SSD. Participants were assigned to either normal-HRTF training or enhanced-HRTF training (n = 10 each). The experiment comprised pre-test, three training sessions, and post-test, and all participants were tested with both normal and enhanced HRTFs, yielding four train-test combinations. Performance was evaluated using accuracy (ACC), mean absolute error (MAE), and response time (RT). Localization performance improved with training under the present VR simulated-SSD condition. ACC increased and MAE decreased from pre-test to post-test, whereas RT showed no clear change. No significant overall between-group difference in cumulative improvement was observed. However, during training, the enhanced-HRTF group showed a significant first-session advantage, and matched train-test combinations showed descriptively larger gains than mismatched combinations. These results suggest that short-term VR localization training can improve directional judgment under simulated SSD and that enhancing monaural spectral cues may provide an early benefit by making direction-specific patterns easier to associate with source direction. The findings are limited to localization performance in the present VR task under simulated SSD and should not be directly generalized to clinical SSD populations, real-world auditory rehabilitation, or broader everyday 3D spatial-audio experience.
