Minimum-Phase HRTF Modeling of Pinna Spectral Notches using Group Delay Decomposition
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Accurate reconstruction of HRTFs is important in the design and development of high quality 3D binaural sound synthesis systems. Conventionally, minimum phase HRTF model development for reconstruction of HRTFs has been limited to minimum phase-pure delay models which ignore the all pass component of the HRTF. In this paper, a novel method for minimum phase HRTF modeling of Pinna Spectral Notches (PSNs) using group delay decomposition is proposed. The proposed minimum phase model captures the PSNs contributed by both the minimum phase and all pass component of the HRTF thus facilitating an accurate reconstruction of the HRTFs for all spatial angles which was hitherto not possible in the minimum phase-pure delay model. The purely minimum phase HRTF components and their corresponding spatial angles are first identified using a Fourier Bessel Series method that ensures a continuous evolution of the PSNs. The minimum phase-pure delay model is used to reconstruct HRTF for these spatial angles. Subsequently, the spatial angles which require both the minimum phase and all pass component of the HRTF are also identified. For these spatial angles, a second order all pass filter is cascaded with the minimum phase-pure delay HRTF model. The all pass filter designed in this work captures the spectral cues contributed by the all pass component of the HRTF. The minimum phase HRTF model proposed in this work is able to reconstruct accurate HRTFs since it is able to capture PSNs with a high degree of resolution. Performance of the proposed minimum phase HRTF model is evaluated by conducting experiments on PSN extraction, cross coherence analysis, and 3d binaural sound synthesis. Both objective and subjective evaluation results obtained using CIPIC, KEMAR, and the MiPS database are used to indicate the significance of the proposed model in 3D binaural sound synthesis.
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