The Csound reson and butterworth filters are all 2^nd order, so you can check them out in the sources.

 

But if you’re looking for simple C code, not tied to Csound, I’ve found this book useful: “C Language Algorithms for Digital Signal Processing” by Paul Embree:

 

https://www.amazon.com/Language-Algorithms-Digital-Signal-Processing/dp/0131334069

 

He also has some more recent books advertised on the same page, which look interesting, but I haven’t read them.

 

From: A discussion list for users of Csound [mailto:CSOUND@LISTSERV.HEANET.IE] On Behalf Of Emmett Palaima
Sent: Thursday, February 16, 2017 10:10 PM
To: CSOUND@LISTSERV.HEANET.IE
Subject: [Csnd] Simple Second Order Lowpass Filter Formula

 

Hi, I'm doing some audio programming in C, and I'm looking for a simple 2nd order lowpass filter design I can implement. Not looking for anything too fancy, just need something like the Tone opcode but with a steeper cutoff. I was looking in the Audio Programming book but it only covers 1st order IIR filters. 

 

Any suggestions?

 

Thanks! 

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