Re: ITDs

[John Culling <cullingj@xxxxxxxxxxxxx>]

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.