Areti Andreopoulou

Identification of perceptually relevant methods of inter-aural time difference estimation

The inter-aural time difference (ITD) is a fundamental cue for human sound localization. Over the past decades several methods have been proposed for its estimation from measured head-related impulse response (HRIR) data. Nevertheless, inter-method variations in ITD calculation have been found to exceed the known just noticeable differences (JNDs), leading to possible perceptible artifacts in virtual binaural auditory scenes, when personalized HRIRs are being used. In the absence of an objective means for validating ITD estimations, this paper examines which methods lead to the most perceptually relevant results. A subjective lateralization study compared objective ITDs to perceptually evaluated inter-aural pure delay offsets. Results clearly indicate the first-onset threshold detection method, using a low relative threshold of -30 dB, applied on 3 kHz low-pass filtered HRIRs as consistently the most perceptually relevant procedure across various metrics. Several alternative threshold values and methods based on the maximum or centroid of the inter-aural cross correlation of similarly filtered HRIR or HRIR envelopes also provided reasonable results. On the contrary, phase-based methods employing the integrated relative group delay or auditory model were not found to perform as well.

Identifying a perceptually relevant estimation method of the inter-aural time delay

The Inter-aural Time Difference (ITD) is a fundamental cue for human sound localization. Over the past decades, several methods have been proposed for its estimation from measured Head-Related Impulse Response (HRIR) data. Nevertheless, inter-method variations in ITD calculation have been found to exceed the known Just Noticeable Differences (JNDs), hence leading to possible perceptible artifacts in virtual binaural auditory scenes, even for cases when personalized HRIRs are being used. In the absence of an objective means for validating ITD estimations, this paper evaluates which methods lead to the most perceptually relevant results. A subjective lateralization study compared objective ITDs to perceptually driven inter-aural pure delay offsets. Results clearly indicate the first-onset Threshold detection method, using a low relative threshold of -30 dB, applied on 3 kHz low-pass filtered HRIRs as the most perceptually relevant procedure across various metrics. Alternative threshold values and methods ba...

Contributions of head-related transfer function choice and head tracking to virtual loudspeaker binaural rendering

This presentation will provide an overview of recent and ongoing studies regarding evaluations of sound fields using virtual loudspeaker binaural synthesis. Of specific interest is an identification of perceptual attributes affected by Head-Related Transfer Function (HRTF) choice beyond basic localization error and the sensitivity of listeners to head tracking with regards to latency and externalization judgments. A list of perceptual attributes, created using a Consensus Vocabulary Protocol elicitation method, and validated through listening tests, resulted in eight valid perceptual attributes for describing the perceptual dimensions affected by HRTF set variations. Employing prescribed head movements, sensitivity to head tracker latency showed small but significant differences between single and multichannel audio source scenes. A similar protocol was employed to comparing the sense of externalization as a function of head rotation with and without head tracking. In contrast to several previous studies,...

Feature space minimization and its affect on head related transfer functions clustering

Several approaches have been taken toward data/feature-space reduction in HRIRs, operating either in the time (original, minimum phase, normalized HRIRs) or in the frequency domain (magnitude, log-magnitude, standardized log magnitude HRTFs). Shin and Park (2008) extracted only the response of the pinna (0.23 ms of the original HRIR), Hwang and Park (2007) included also the response of the head and torso (1.5 ms), while Bondu (2006) operated on the first 100 samples of the impulse responses. Other research focuses on employing PCA for minimizing the feature space to 5–12 orthogonal components and their corresponding weights (Langendijk, 2002; Huang, 2009; Hugeng, 2010), while others have managed to isolate directional and non-directional spectral cues of non-individualized HRTFs (Hu, 2008; Diepold, 2010). In previous work, the clustering tendencies of the standardized log-magnitude HRTFs of 110 subjects on the horizontal plane have been demonstrated, by applying k-means on 256-feature filters. In this stu...