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Re: Wasn't v. Helmholtz right?

> Dear Bill,
> thank you for the address! My question rather implicated a judgement by Roy
> Patterson, since I was aware of a poster by S. Fobel, St. Uppenkampf, R.
> Patterson, and B. Kollmeier, entitled Asymmetry in Perception of Short
> Chirp Cignals, presented in Oldenburg, and dealing with two types of
> stimuli. Chirps with rising frequency were calculated to compensate for the
> dispersion of traveling wave. Dau postulated that this up-chirping will
> sound more compact than an ordinary click and much more compact than chirps
> with falling frequency. The opposite seems to be true.
> Concerning the reply by Jont Allen, I feel a little bit embarrassed.
> Fortunately, I have no idea who is suggested to die and why.
> - Eckard

Just for clarification, some short remarks on short chirps with
rising and falling instantaneous frequency:

Dau et al. (JASA 107, pp. 1530-1540, 2000) demonstrated that short
frequency chirps with rising instantaneous frequency designed to compensate
for BM dispersion will increase wave V of the auditory brainstem response,
when compared to click reponses. ABR to time reversed ("down-") chirps
shows less synchronisation than a click response. This is a nice and
very clean result which can be explained by increased synchronisation
of the low frequency channels in case of the up-chirps. It does, however,
not include any "postulate" of how these signals sound like (and therefore
there is nothing on sound quality in that paper).

When listening to these synchronising chirps and its time-reverse,
it is obvious that up-chirps sound less like a click than down-chirps,
despite the increased synchronisation of BM sections (as reported on
that poster at the DAGA meeting in Oldenburg this year). We interprete
this finding as indication for a process of temporal integration
beyond the structures generating ABR wave V, that transforms the time
code into a time-interval code - effectively removing between-
channel phase differences while preserving within-channel fine
structure. More on this during the forthcoming ISH meeting in Mierlo

Stefan Uppenkamp