It is well known that there is substantial sensitivity to ITD for signals at all frequencies. At higher frequencies, the information is encoded in the envelope rather than in the carrier. This follows directly from the inability of the system to encode the phase of the carrier at higher frequencies – an issue the envelope encoding avoids. Some references: Henning, G. B. 1974 Detectability of interaural delay in high-frequency complex waveforms. J . Acoust. Soc. Am. 55, 84-90. Bernstein, L. R., Trahiotis, C., 2002. Enhancing sensitivity to interaural delays at high frequencies by using “transposed stimuli”. J. Acoust. Soc. Am. 112, 1026–1036. ------------------------------------------------------- Frederick (Erick) Gallun, PhD Portland VA Medical Center Associate Professor, Dept. of Otolaryngology and Neuroscience Graduate Program Oregon Health & Science University From: AUDITORY - Research in Auditory Perception [mailto:AUDITORY@xxxxxxxxxxxxxxx] On Behalf Of James Johnston Well, having read more than one paper saying that there are no time cues above 2kHz (or 3kHz, take your choice) I offer everyone the following challenge. On Sun, Jul 27, 2014 at 3:21 AM, Enda Bates <enda.bates@xxxxxxxxx> wrote: Hi Philip, yeah there's been quite a bit of work on this type of thing in audio research. You are also basically correct in that a phantom source will be a little broader than a real source, largely due to the fact that the localization of phantom sources is somewhat frequency dependent. Straightforward amplitude panning will produce a slight discrepancy between the localization at low and high frequency ranges, which leads to a slight change in timbre (manifests as a slight spectral dip at approx. 2kHz) and an increase in the Apparent Source Width (ASW) of the source when it is reproduced as a phantom image. This is a big problem when dynamically panning a sound as this change in timbre tends to highlight the loudspeakers in a negative way and it significantly reduces the smoothness of the spatial trajectory (incidentally, one the main goals of the Ambisonics spatialization system was to eliminate this issue, which it largely does but not without some costs). Ville Pullki has done a lot of research in this area, particularly in terms of his amplitude panning system VBAP. He has also conducted research on panning using three loudspeakers (again with VBAP). My recollection is that this will increase the ASW even further, and similarly reduce localization accuracy. Of course there is a strong relationship between the two factors, and the concept of locatedness is useful in this regard. Anyway, chapter 6 my PhD thesis has lots of specific references in terms of listening tests with phantom sources and the relationship between localization accuracy and apparent source width, both for stereophony and ambisonics. You can find it here -> http://endabates.net/academic.html Hope that helps, Dr. Enda Bates Music & Media Technology, Trinity College Dublin On 26 July 2014 16:45, William Yost <William.Yost@xxxxxxx> wrote: Fine work in Journal of the Acoustical Society of America by Wes Grantham William Yost Office: 480-727-7148 Home: 480-306-6755 Cell: 480-231-9250
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James D. (jj) Johnston Independent Audio and Electroacoustics Consultant |