I take it you're using this formant table:

https://www.classes.cs.uchicago.edu/archive/1999/spring/CS295/Computing_
Resources/Csound/CsManual3.48b1.HTML/Appendices/table3.html

The Hz-to-Q conversion is described in the caption of the illustration here:

https://en.wikipedia.org/wiki/Q_factor

-3dB attenuation is the usual passband threshold, as discussed further in
the link below, and I expect (?) it's appropriate to use with the present
values.

https://en.wikipedia.org/wiki/Bandwidth_(signal_processing)

A secondary issue is the choice of waveform to feed into a formant filter,
and how to approximate a real "glottal pulse".  There is some interesting
discussion here

http://clas.mq.edu.au/speech/acoustics/frequency/source.html

building on work in this old paper

https://pdfs.semanticscholar.org/e504/38c1e56d4ce3f7ebe3d10cea483ea38234c6.pdf





On Tue, Feb 6, 2018 at 8:56 PM, Frank Sheeran <fshee...@gmail.com> wrote:

> I'm hoping to make some formant synthesis patches with my modular soft
> synth Moselle. http://moselle-synth.com
>
> I've looked around for formant tables and find tables with more vowels and
> fewer formants, or fewer vowels and more formants.  Tables with amplitude
> seem to have fewer vowels and only one I've found shows Q.
>
> But the Q (as shown in CSound documentation, one example pasted below) is
> specified in Hz.
>
> The parametric (const and non-const) filters I'm using need a Q input.  Is
> there a formula to convert Hz into Q?
>
> Failing that, is there a standard amplitude at which which a bandwidth
> would be measured in Hz?  EG, at -6dB or -12dB or something?  If so I could
> just eyeball it on a graph.
>
> Final question: does anyone know a more comprehensive set of such data?
> This CSound data is great but only covers 5 vowels.
>
> Frank Sheeran
>
>
> *soprano "a"*
> freq (Hz)  800  1150  2900  3900  4950
> amp (dB)  0  -6  -32  -20  -50
> bw (Hz)  80  90  120  130  140
>
>
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