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Pitch in a non-animate world

Dear list,

The discussion on the interrelationships of animals with the sounds of
their natural environments has interesting implications. I think it should
be pursued. Here's a simplistic version of my thinking.

Animals evolved "ears" as a sensor to enhance survival. To do this each
species has evolved auditory processing technology to handle problems
peculiar to its environmental niche. Each niche imposes auditory
requirements and constraints that are increasingly demanding in proportion
to each evolutionary level.

As Al has pointed out, animal-free environments have essentially no
periodic or tonal sources. Periodic sounds have appeared as a result of the
evolution of animals. To an animal, tonal or impulsive events in the
natural environment have usually represented significant threats to
survival. Tonal/periodic sounds as well as impulsive sounds therefore
represent animals that are either threats or benefits. Thus, ears,
especially in mammals, have evolved technology that can extract meaning
from both tonal and atonal sounds, not to mention the fact that the sounds
are generally intermixed...the well-known acoustic scene. To accomplish all
this the ear's processing methods, regardless of species, have responded
successfully to conflicting fundamental requirements in time and frequency.
For example, temporal requirements for locating sounds impose extremely
fast response times that are incompatible with the frequency domain...And
then there's the problem of unravelling mixed spectra in informational
masking. The question is: How have animals been able to resolve this conflict?

One should ask whether the cochlea really does a spectral analysis or
whether some kind of an alternative processor is subtly in place.


John Bates