Hi community.

Looking to implement a particular high-pass filter. See attachment for graphs.

6khz cut off, 1.5db slope. Low frequencies experience an almost 180 degrees phase-shift. The amount of phase shift decreases as the frequency is increased.

Any ideas?

http://www.pdpatchrepo.info/hurleur/Screen_shot_2013-08-13_at_12.20.07.png

Hi community,

Trying to create a waveshaper using a sigmoid transfer function. Have read miller puckette's book and looked at the examples, but can't seem to get to grips with how to get my sigmoid function to write to an array.

The function i'm looking to use as my waveshaper is:

F(f)=h+k tanh⁡(f)

Attached is a graphical version.

Any help would be great!

http://www.pdpatchrepo.info/hurleur/Screen_shot_2013-07-10_at_16.53.53.png

Hi community.

I have 3 filters that I need to design and need some help just implementing them in Pd. Two are boundary loss filters and one is a DC killer (implementation within a waveguide model).

Here's the details of the filters:

1. 0.376/1-.6^z-1 (low-pass)
2. 1.8417+ z^-1/1 (low-pass)
3. 1-z^1/ 1-.995z^1 (dc block)

Any help would be grateful, but any form of walk through to implement these filters in pd would be great. Attached is the image of the waveguide being created.

Cheers!

http://www.pdpatchrepo.info/hurleur/Screen_shot_2013-07-03_at_14.04.30.png

Hi community

Anyone had any success with waveguide modelling in puredata?

I'm developing a waveguide model for a Flute at the moment. Had moderate success but wondered if anyone had any patches to share? I've seen Kim Taylors work on here before but wondered if anyones had any other successful examples?

Hi community.

I'm trying to implement a sigmoid transfer function for my audio input. The function I need to use is:

F(f) = h + ktanh(f)

I've tried to implement it in pd (see attach) but not sure that what i've done is correct. I also wasn't sure if there were any sigmoid objects already out there in pd land.

Any thoughts?

http://www.pdpatchrepo.info/hurleur/sigmoid.pd

Hi community,

I'm having trouble compiling bensaylor's [partconv~] object.
(http://puredata.info/Members/bensaylor/partconv~-0.2.tar.gz/file_view)

I've gone into the directory, ran make and then pd_darwin but pd still doesn't seem to recognise the object.

I have also ran the FFTW mentioned in the description.

Can anyone talk me through what I should be doing/ am doing wrong?

Cheers

Has anyone come across successful methods for lagrange interpolation/thiran allpass filters on pd?

The delwrite argument initialises the buffer with a maximum delay value. In the example above, you've created a buffer length 1000ms, and the delread reads/taps/outputs from an index 500ms along the buffer.

Hope that makes sense? Read puckette's book on delay lines if you want any more meaty information.

Any thoughts?

I believe that is the one. Any ideas on how to implement something like that or the one outlined in the first post?

I'm modelling a pipe of radius 9.4. I already have a filter implemented already, which Maelstorm you may recall, but I wanted to know more about the phase change.

I did have a quick look for it but couldn't find anything. I'd hoped it was a stock matlab object, but I know nothing of matlab so I take it it isn't!

What I can give you though is the bit of text from the thesis i'm citing.

"The characteristics of the reflection filter depend on the geometrical dimensions of the bore. Irish whistle bore radius is equal to 7,5 mm. Scavone in [6] provides a function which takes the pipe radius and calculates coefficients of an arbitrary order digital filter using the invfreqz function. Figure 3.7 presents the transmittance of the second-order digital filter corresponding to the Levine-Schwinger solution for an unflanged cylindrical pipe of radius 7,5 mm."

Hopefully this is of help!

Hello guys.

Sorry to bring an old topic back from the dead, but is it possible, in particularly for the low pass filters (1 and 2) to derive the cut-off frequency/3db point for each or is that something you have to take from drawing the function?

I'm using this transfer function within a flute waveguide. Here's the excerpt about the transfer function.

"where f is the value of the volume flow advancing towards the
embouchure hole, k is a gain term, and h describes the deviation
of the center line of the air jet from the wedge. By changing the value of h it is possible to produce asymmetrical wavefom or- in other words - sounds that also have even harmonics in their spectrum. When h is zero, the spectrum of the output of the model has very weak even harmonics"

Admittedly the following excerpt is about another slightly different function (see screenshot), but the idea is still the same.

f(x) = -1 if x<= -1.325
x^3-x if 1.325<x<-1.325
1 if x>=1.325

"If the input signal does not go beyond (-1.325,1.325) range the waveshaper inverts the phase of the input signal and introduces a third harmonic. Once the range is exceeded, hard limiting occurs and inserts odd harmonics from clipping."

http://www.pdpatchrepo.info/hurleur/Screen_shot_2013-07-12_at_10.31.44.png

Hi mod, thanks for the swift reply!

Here's my sigmoid transfer function for the equation written in my first post. Maybe i'm missing something, but I can't seem to get it to work properly. It just seems to move the waveform up and down by the factor of H which says to me the tanh isn't functioning. It's probably something very elementary, but i've got myself in a muddle trying to work it out through looking at other examples and now i'm a little lost with it.

http://www.pdpatchrepo.info/hurleur/sigmoid.pd

That's great, thanks Maelstorm. Life saver.

Sweet, thanks for the input. Any ideas for the others?

Maelstorm, any ideas?

Any thoughts?

Well you certainly know more about them than I do Maelstorm! Anyway. The last attempt I made at an interpolation filter was 4-point lagrange, but as I said, it was pretty clumsy and i'm not entirely sure it functioned properly as it was a pretty rushed effort!

Anyway i've attached it just so you could get a look. Maybe you can see where things went wrong.

And Arnaud, thats great that you've got experience and thanks for the pdf, but my french is far from workable so as much as I partly recognise some of the maths, there's not much I can extract from it. Did you produce your waveguide in pd?

Basically this is all for a flute waveguide i'm currently working on thats having a few teething issues to say the least. In it's current form it kind of sounds like a flute, but doesn't behave as such. For example once you create the resonance, turn off the air jet or excitation, the tone should stop because nothing is keeping the resonance going, yet this doesn't happen, which says to me some form of missing link in the loss filters. I recon it's the fairly dramatic oversimplification of the filter thats causing it, but wondered if any of you guys would take a look?

Should I post the waveguide on here or make another topic, Maelstorm?

http://www.pdpatchrepo.info/hurleur/4FIR.pd

Thanks Maelstorm. Will try that out. I've come to be believe that you're an expert on filters.

Have you had/seen any successful fractional delay interpolation filters in pd? I made one last year, but it was pretty clumsy. Wondered if you know of any good ones.