Hi, somebody pointed out to me that there are already the filter-graph-1 and filter-graph-2 abstractions for plotting frequency responses of filters They seem to work by doing a frequency sweep in a way similar to spectrum analysers,.

/doc/3.audio.examples/H13.butterworth.pd has a nice example of it.

You are right about the aliasing if the filter's stop band isn't attenuating enough. I was counting on the aliased signal energy being negligible. I am going to give the impulse response approach a try nevertheless and maybe compare it to the frequency sweep method.

Thanks for the answer!

Thanks a lot @whale-av ! I definetly remember seeing Katja's page before. It is a wonderful resource. I will dig a little bit into it to see if I can come up with something more elegant for my frequency response graphs. My problem is not actually with understanding the filter behaviour itself or the trade-offs but more of implementing nice "visualization" or debugging tools in pd.

Thanks for the hints!

Hi, I am conducting a little study on filters and currently finding a way to obtain their frequency response by feeding them a wideband signal and plotting their FFT.

I am new to the PD environment and currently the best I could do is generate N/2 oscillators with different frequencies (N being the sample size of the audio buffer). I am sure there is a smarter way of doing this (generating lists for the oscillator frequencies and/or sequencing them). Any suggestions?

I could write an external but a relatively simple subpatch or expression is better.

As an alternative I could feed white noise and average the FFT curves over time, but the result would not be as smooth.

Thank you!

lop_example.pd

Hi, has anyone tried to make bode plots? Which techniques have you used/heard of for best characterizing filters within the environment?