Subject: Re: ITDs From: =?ISO-8859-1?Q?Martin_Ekl=F6f?= <martin.eklof@xxxxxxxx> Date: Wed, 23 Sep 2009 12:46:33 +0200 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Dear David, Maybe this is too basic but for completeness: One reason that high frequency sinusoids does not provide reliable ITD clues is the fact the distance between the ears is limited (~23 cm). This yields a maximum ITD of 690 us. Which in turn corresponds to more than one period of a 1500Hz sinusoid so a certain ITD can correspond to more than one angle. The ITD gets more and more ambiguous as the frequency goes beyond that. See pages 236-237 in "An introduction to the Psychology of Hearing", Brian CJ Moore Best regards, Martin Eklöf ________________ MSc Karolinska University Hospital, Huddinge Cochlear implant clinic, M43 http://www.karolinska.se/ci martin.eklof@xxxxxxxx Tel: +46(0)8 - 585 89 329 Fax: +46(0)8 - 585 87 960 AUDITORY - Research in Auditory Perception <AUDITORY@xxxxxxxx> skrev 2009-09-23 10:20:22 : > Re: [AUDITORY] ITDs > John Culling > 2009-09-23 10:29 > > ITD is not an effective cue at high frequencies for pure tones, > but other waveforms - noise bands, high-pass-filtered clicks > and particularly "transposed stimuli" (cf. JASA papers by > Bernstein, van de Par etc.) - it is still effective. > > The reason it is not effective for pure tones is > presumed to be the fact that there is a loss of phase-locking to > the fine structure of the stimulating waveform at stages of the > auditory system that precede binaural interaction. It is known, > for instance, that the capacitance of inner hair cells prevents > their intracellular potential from following carrier frequencies > in excess of 4-5 kHz in mammals. This results in a corresponding > loss of encoding on the auditory nerve. Carrier ITDs cease to be > effective above about 1500 Hz, however, so there may be > further losses upstream. ITDs encoded by the waveform > envelope (which are present for noises, clicks etc.) are not > subject to this limitation, > > John. >