- ... Abel1
- Work supported in part
by San Jose State University Cooperative Agreement NCC-2-327.
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- ... plane2
- Note that the image of the conformal map
corresponds to the domain variable of the allpass
transformation, while the input of the map corresponds to the
range variable z.
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- ... desired.3
- In
general, the unit circle is mapped once to itself by any allpass
transformation for which the number of poles Np minus the number of
zeros Nz inside the unit circle is |Np-Nz|=1. Therefore, higher
order allpass transfer functions can be used having Np poles inside the
unit circle, say, and
poles outside the unit circle.
However, such a transformation cannot be used for audio digital filter
design, our principle application, because it results in an unstable final
filter
. It similarly cannot be used in any
applications requiring time-domain implementation of the unstable allpass
filter in place of a unit delay element.
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- ... Barks4
- The
normalized warped-frequency interval
was converted to
Barks b by the affine transformation
,
where Nb is the number of Bark bands in use. For example, Nb=25 for
a 31 kHz sampling rate.
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- ...JOST:5
- Matlab functions bark2lin.m and lin2bark.m for transforming between linear and bark-warped frequency
representations are available on the internet at http://ccrma.stanford.edu/~jos/bbt/bbt.html.
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