From: Mikael Ogren <mikael@bu...> - 2006-10-20 07:07:47
My name is Mikael, and I am a scientist/engineer working with acoustics. =
have used Audacity a lot for mixing sounds of different kinds, but have
used other proprietary software for analysis such as A-weighted levels,
octave band levels and so on. But I have realized that using a Nyquist
plug-in such an analysis would be a simple thing to add to Audacity.
However, I quickly reached the point were I got stuck, and hence I=92m
sending this mail to ask for help.
I would like to filter a signal in my Nyquist plugin with a set of digita=
filter coefficients (often called =93a=94 and =93b=94 coefficients). This=
possible in Nyquist, since all the filters use this approach, but I have
found no way of directly giving values for the coefficients a and b. All =
can find in the Nyquist documentation and the source code of other
plug-ins is filter functions where you give transition frequencies and
such, and then the low level stuff including calculating the coefficients
gets done automagically.
Beeing more specific: I have two different filters I would like to
implement, one being the A-weighting filter (see
http://en.wikipedia.org/wiki/A-weighting). I have made a bilinear
approximation which uses five =93a=94 and seven =93b=94 coefficients, how=
filter a signal with these home-made coefficients in Nyquist?