in the weighted equation error solution (E.3.1) can be
multiplied by any desired application-dependent weighting.
Audio conformal maps can be adjusted by using a more general error
weighting versus frequency. For example, the weighting can be set to
zero above some frequency limit along the unit circle. A more general
weighting can also be used to obtain improved accuracy in specific
desired frequency ranges. Again, these refinements would seem to be
of interest primarily for the ERB-scale and other mappings, since the
Bark-scale warping is excellent already. The diagonal weighting matrix
in the weighted equation error solution (E.3.1) can be
multiplied by any desired application-dependent weighting.
As another variation, an auditory frequency scale could be defined
based on the cochlear frequency-to-place function [96].
In this case, a close relationship still exists between equal-place
increments along the basilar membrane and equal bandwidth increments
in the defined audio filter bank. Preliminary comparisons
[96, Fig. 9] indicate that the first-order conformal map
errors for this case are qualitatively between the ERB and Bark-scale
cases. The first-order conformal map works best when the auditory
filter bandwidths level off to a minimum width at low frequencies, as
they do in the Bark-scale case below 
Hz. Thus, the question of
the ``audio fidelity'' of the first-order conformal map is directly
tied to the question of what is really the best frequency resolution
to provide at low frequencies in the auditory filter bank.
