[sdiy] math question - somewhat OT

[jbv]

Magnus,

thanks for the reply.
yes, that's what I'm looking for.
But I actually need to know the mathematical way
to compute that for a software routine that will
draw any freq on a log scale.

for instance, if I have 3 freqs (190Hz, 445Hz, 895Hz),
I want that routine to draw each freq at their exact position
on a scale in which perfect partials (220, 440, 880) would
have equal distance of 100 pixels.
so the distance between 190 and 445 would be 107 pixels,
and the distance between 445 and 895 would be 109 pixels
(these aren't the right values, I'm just throwing in these
figures for the example).

Thanks,
JB

>
> > Hi folks,
> >
> > I have a blank.
> > I want to represent frequencies (partials of a sound
> > for instance) on a linear scale (instead of exponential).
> > IOW the distance between the following values :
> > 220, 440, 880, 1760 should be equal (but the freqs
> > aren't always perfect harmonics values).
> > How do I compute that ?
>
> If you want "equal distance" you GOT to do it on a logarithmic scale.
> The only thing you do is to mark it by the non-logaritmized values.
>
> So, let's say that 220 Hz is on the 3rd mark, 440 Hz is on the 4th mark and
> 880 Hz is on the 5th mark, each mark being say 1 cm apart, then you just write
> 220 Hz on the 3rd mark, 440 Hz on the 4th mark and 880 Hz on the 5th mark.
> The scale is logarithmic, but the scale marking isn't. Ain't that confusing?
>
> Now, is that what you are looking for (but maybe not expected)?
>
> If not, describe better what you are after.
>
> Cheers,
> Magnus