Acoustic and non-acoustic factors in modeling listener-specific performance of sagittal-plane sound localization

Abstract

The ability of sound-source localization in sagittal planes (along the top-down and front-back dimension) varies considerably across listeners. The directional acoustic spectral features, described by head-related transfer functions (HRTFs), also vary considerably across listeners, a consequence of the listener-specific shape of the ears. It is not clear whether the differences in localization ability result from differences in the encoding of directional information provided by the HRTFs, i.e., an acoustic factor, or from differences in auditory processing of those cues (e.g., spectral-shape sensitivity), i.e., non-acoustic factors. We addressed this issue by analyzing the listener-specific localization ability in terms of localization performance. Directional responses to spatially distributed broadband stimuli from 18 listeners were used. A model of sagittal-plane localization was fit individually for each listener by considering the actual localization performance, the listener-specific HRTFs representing the acoustic factor, and an uncertainty parameter representing the non-acoustic factors. The model was configured to simulate the condition of complete calibration of the listener to the tested HRTFs. Listener-specifically calibrated model predictions yielded correlations of, on average, 0.93 with the actual localization performance. Then, the model parameters representing the acoustic and non-acoustic factors were systematically permuted across the listener group. While the permutation of HRTFs affected the localization performance, the permutation of listener-specific uncertainty had a substantially larger impact. Our findings suggest that across-listener variability in sagittal-plane localization ability is only marginally determined by the acoustic factor, i.e., the quality of directional cues found in typical human HRTFs. Rather, the non-acoustic factors, supposed to represent the listeners' efficiency in processing directional cues, appear to be important.

Modeling Localization of Amplitude-Panned Virtual Sources in Sagittal Planes

“…In stage 5 these distances are mapped to similarity indices that are proportional to the predicted probability of the listener's polar-angle response. The shape of the mapping curve is determined by a listener-specific sensitivity parameter that represents the listener-specific localization performance to a large degree [13]. In stage 6 monaural spatial information is combined binaurally whereby a binaural weighting function accounts for a dominant contribution of the ipsilateral ear [15].…”

“…This model has been extensively evaluated in previous studies [12,13]. Our investigation was subdivided into two parts.…”

Effects of hearing-aid dynamic range compression on spatial perception in a reverberant environment

“…Individual BRIRs were used since it has been shown that the use of individual head-related transfer functions (HRTFs), the Fourier transformed head-related impulse responses, improve sound localization performance compared to non-individual HRTFs (e.g., Majdak et al, 2014), as a result of substantial crossfrequency differences between the individual listeners' HRTFs (Middlebrooks, 1999). Individual BRIRs were measured from the loudspeakers placed at the azimuth angles of 0, 30, 150 180, 240, and 300 deg.…”

JND-based spatial parameter quantization of multichannel audio signals

“…In some experiments on sound source localization, laser pointer-based methods [33][34][35] are often used to locate the exact location of sound source perceived and pointed by listeners. Since we mainly focus on the difference of perceived virtual sound location between processed and unprocessed multichannel audio excerpts, the listener just needs to tell how about the differences, obvious or not.…”