Our ability to localize sounds is based on the relative time and level differences between the wavefronts arriving at the two ears. These parameters are measured as interaural time difference (ITD) and interaural level difference (ILD), respectively. ITD is the dominant cue at low frequencies and ILD is more important at high frequencies. ITD is of the order of less than a millisecond and is difficult to estimate based on sampled data. We consider the problem of ITD estimation and show that the ITD manifests as a change in the zero-crossing rate (ZCR) of the head related transfer functions (HRTFs). As a result, it becomes possible to estimate the ITD precisely by comparing the ZCRs of the left and right HRTFs. Our experimental results indicate that zero-crossings of the HRTFs alone (which are devoid of amplitude information) contain sufficient information to estimate ITD as reliably as the state-of-the-art techniques.
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