[Fluxus] puzzle

[Kassen]

2010/1/18 evan.raskob [lists] <lists at lowfrequency.org>

> Usually it's as Kassen said - looks like an exponential curve to me, but
> the theory behind it is that the frequency bands should be double with each
> step, like Kassen said.


I don't think they need double; that would put a lot of the bands in a
extremely low range for higher numbers of bands. If we have a grand piano
and split the keyboard into 8 sections then they indeed double for every
section (give or take a few keys). If we'd split it equally into more
sections then clearly they won't double per band any more (instead the
factor becomes some number between 1 and 2). For less bands the step per
band would be some factor over 2.


I don't think it makes much sense to consider DC offset ( 0 Hz) because
general purpose adc's can't reach that anyway, 20Hz as a lowest frequency
and the Nyquist as a upper bound makes more sense to me. I assume we can
poll Jack for the sample-rate, 20Hz as a lower bound is a constant so from
there on the band width will follow from the desired number of bands.

Instead of trying to deal with unequal band distribution for variable band
numbers we could also make it set a number of bands that would default to a
equal distribution, then have bands that are movable from code. This would
enable us to focus on certain regions, for example when working with a live
acoustical instrument with a limited frequency range. Conditions like that
can't really be anticipated; what's reasonable for electronic dance music
will not be for solo piccolo performance. It might also be interesting to
try to get the most prominent frequency from the fft as a exact number
(instead of a approximation by band) so we could track that too. If we are
already spending the cpu on a fft analysis we might as well try to get as
much from it as we can.

Yours,
Kas.
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