Re: maximum tatum (one tatum, two tata) (Eckard Blumschein )

Subject: Re: maximum tatum (one tatum, two tata)
From:    Eckard Blumschein  <Eckard.Blumschein(at)E-TECHNIK.UNI-MAGDEBURG.DE>
Date:    Wed, 10 Apr 2002 09:54:37 +0200

When I swept across the white keys about 50 years ago, I already expected the tones like a spectrum of colors to orderly change step by step. So I also imagined not to miss any tone. Obviously, parallel processing allows to perceive many colors (tones) almost at a time. On the other hand, a regular series of less than 40 light flashes (sound onsets) causes a superimposed typical flicker (rattling noise). I was unable to count the number of the together perceived tones. Meanwhile, I try to understand the limitations separately. Cortical limitation: If perception merely relies on distinction between only two different colors, durations, or intensities, then I guess, a limit of 10 Hz might be a reasonable estimate due to cortical sluggishness. In simplifying words: Attention of the central nervous system is typically limited to less than ten subsequent pictures a second. Conductors of an orchestra might just be able to ramify these pictures. Cochlear limitations: Even if the auditory snail is by far the fastest organ of our body, I agree with John Bates in that the traditional notion of hearing by spectral analysis in cochlea fails in case of rapidly changing signals. Well, we are certainly able to hear at least 25-ms and possibly 12.5-ms intervals between consecutive piano tones, and there is evidence for perception of much smaller ITDs. Why does this not apply for very deep or very high tones and also not for very high intensities? Aage Moller wrote: 'Cochlear spectral filtering may be important for temporal coding', and he referred to the pertaining phenomenon as 'synchrony capture'. I called it the temporal aspect of spectral code. Divenyi explained it best: The listener can use envelope analysis within similar spectral bands. Perhaps, most of so called cochlear limitations are actually set by refractory time in the auditory nerve. This might be the decisive bottleneck rather than limitations to cochlear mechanics, cochlear amplifier or nuclei of midbrain. Eckard

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