title: Computational models for listener-specific predictions of spatial audio quality
Creators: name: Majdak, Piotr
name: Baumgartner, Robert
Publisher: name: EAA Spatial Audio Signal Processing Symposium
Year: 2019
Subjects: sound externalization
spatial hearing

description: Millions of people use headphones every day for listening to music, watching movies, or communicating with others. Nevertheless, sounds presented via headphones are usually perceived inside the head instead of being localized at a naturally external position. Besides externalization and localization, spatial hearing also involves perceptual attributes like apparent source width, listener envelopment, and the ability to segregate sounds. The acoustic basis for spatial hearing is described by the listener-specific head-related transfer functions (HRTFs, Moller et al., 1995). Binaural virtual acoustics based on listener-specific HRTFs can create sounds presented via headphones being indistinguishable from natural sounds (Langendijk and Bronkhorst, 2000). In this talk, we will focus on the dimensions of sound localization that are particularly sensitive to listener-specific HRTFs, that is, along sagittal planes (i.e., vertical planes being orthogonal to the interaural axis) and near distances (sound externalization/internalization). We will discuss recent findings from binaural virtual acoustics and models aiming at predicting sound externalization (Hassager et al., 2016) and localization in sagittal planes (Baumgartner et al., 2014) considering the listener's HRTFs. Sagittal-plane localization seems to be well understood and its model can already now reliably predict the localization performance in many listening situations (e.g., Marelli et al., 2015; Baumgartner and Majdak, 2015). In contrast, more investigation is required in order to better understand and create a valid model of sound externalization (Baumgartner et al., 2017). We aim to shed light onto the diversity of cues causing degraded sound externalization with spectral distortions by conducting a model-based meta-analysis of psychoacoustic studies. As potential cues we consider monaural and interaural spectral-shapes, spectral and temporal fluctuations of interaural level differences, interaural coherences, and broadband inconsistencies between interaural time and level differences in a highly comparable template-based modeling framework. Mere differences in sound pressure level between target and reference stimuli were used as a control cue. Our investigations revealed that the monaural spectral-shapes and the strengths of time-intensity trading are potent cues to explain previous results under anechoic conditions. However, future experiments will be required to unveil the actual essence of these cues.ReferencesBaumgartner, R., Majdak, P. (2015): Modeling Localization of Amplitude-Panned Virtual Sources in Sagittal Planes, in: Journal of Audio Engineering Society 63, 562-569.Baumgartner, R., Majdak, P., and Laback, B. (2014). "Modeling sound-source localization in sagittal planes for human listeners," The Journal of the Acoustical Society of America 136, 791-802.Baumgartner, R., Reed, D. K., Toth, B., Best, V., Majdak, P., Colburn, H. S., and Shinn-Cunningham, B. (2017). "Asymmetries in behavioral and neural responses to spectral cues demonstrate the generality of auditory looming bias," Proceedings of the National Academy of Sciences 114, 9743-9748.Hassager, H. G., Gran, F., and Dau, T. (2016). "The role of spectral detail in the binaural transfer function on perceived externalization in a reverberant environment," The Journal of the Acoustical Society of America 139, 2992-3000.Langendijk, E. H., and Bronkhorst, A. W. (2000). "Fidelity of three-dimensional-sound reproduction using a virtual auditory display," J Acoust Soc Am 107, 528-37.Marelli, D., Baumgartner, R., and Majdak, P. (2015). "Efficient Approximation of Head-Related Transfer Functions in Subbands for Accurate Sound Localization," IEEE Transactions on Audio, Speech, and Language Processing 23, 1130-1143.Moller, H., Sorensen, M. F., Hammershoi, D., and Jensen, C. B. (1995). "Head-related transfer functions of human subjects," J Audio Eng Soc 43, 300-321.