Head-related impulse response (HRIR) describes the acoustic effects of the physical reflection and refraction around the listener's head and ears on a free-field sound. Exploring the structure of HRIR is crucial for understanding the directional perception mechanism in hearing and for achieving high-precision binaural sound field reproduction. Interaural time difference (ITD) is an important cue for sound localization in binaural hearing, especially for azimuth direction. The frequency dependence of the ITD has been known for several decades, and such frequency-dependent temporal responses possibly provide cues to elevation angle. Standard time- and frequency-domain analyses are difficult to apply to the frequency-dependent response of HRIRs. However, linear time-frequency analysis methods such as short-time Fourier transform (STFT) are not suitable for analyzing short-term HRIRs due to uncertainties in time and frequency. In this study, we investigate the frequency dependence of the propagation time of HRIRs using the second-order time-reassigned synchrosqueezing transform (TSST2). TSST2 can estimate the time of arrivals robustly against the influence of the rear components.
Kusano et al. (2025) studied this question.