Re: [Audacity-quality] ERB scale

[Paul L. <pau...@gm...>]

On Mon, Aug 31, 2015 at 1:17 PM, Steve the Fiddle <ste...@gm...>
wrote:

> On 31 August 2015 at 16:18, James Crook <cr...@in...> wrote:
> > On 31/08/2015 16:00, Peter Sampson wrote:
> >
> > Hi Paul,
> >
> > I've been doing my best to update the page in the 2.1.2 Manual
> > for Spectrograms Preferences:
> > http://manual.audacityteam.org/man/Spectrograms_Preferences
> >
> > I got fairly stuck on the various Scale and Algorithm settings, but
> ploughed
> > ahead with Wikipedia as "my friend" - so it *will* need a fair bit of
> > editing
> > in those two sections.
> >
> > In particular I note that Wikipedia refers to:
> >  "equivalent rectangular bandwidth or ERB"
> >
> > On this basis it seems to me that perhaps your nomenclature for ERBS
> > is tautologous in its use of the final S for scale - i.e. a scale which
> is
> > ERB
> > Scale. And thus the  name for this scale might be better as simply "ERB".
> >
> > And this is an allowably fixable item under semi-freddo.
> >
> > Not just allowable.  If these kind of changes are wanted/valid/correct,
> > positively encouraged.
> >
> > Later, in Frozen, it's more locked down.  P1 fixes in Frozen are always
> > automatically OK.  P2s are generally good, but ask first.
> >
> > The RM.
> >
>
> I've been looking at this to see if I can help Peter with it, and
> there is something very confusing here:
>
> The Spectrogram "preferences" and track "settings" refer to "Scale",
> which I think suggests that it is referring to the scale of the
> vertical track ruler. However, the units of the vertical ruler are not
> the units of the scale.
>
> Example:
> This image from Wikipedia indicates that 3500 Hz is approximately 2000
> mel, https://upload.wikimedia.org/wikipedia/commons/a/aa/Mel-Hz_plot.svg
> yet in the track Spectrogram view, a frequency of 3500 Hz is shown
> with a value of "3500" (Hz) on the vertical ruler, not "2000" (mel).
>

It has also been true that log(f) was a choice, and the height the a
frequency plots to is proportional to its logarithm, but the vertical ruler
is labelled with Hz or kHz.

The relabelling of the ruler is a future project.


>
> "1/f" is also confusing because the inverse of a large number is a
> small number, but it is not shown that way.
>

I said I wanted to change that to "Period" and I have done so.  In this
case the distance of a frequency from the top of the fully zoomed-out scale
is inversely proportional to frequency, or directly proportional to
period.  It is true that periods decrease rather than increasing then as
you ascend the scale.  But I can't think of a better short name than
"period."


>
> Steve
>
>
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