Periodic artifacts on output of IIR Filter

Hello,

you don't describe the "artifacts" in detail. Are this low amplitude "limit cycles"? Basically, the filter must have some resolution extra internally to be accurate up to the resolution of input/output signal. If so, and with appriorate rounding at the ouput, limit cycles should disappear at the output. I noticed, that the referenced literature isn't discussing quantization effects in filter design, also in Matlab or Octave simulation, they would be ignored unless you particularly simulate fixed point arithmetics. For an exact simulation of quantization noise, overflow, and possible limit cycles or even dynamic instability this would be necessary.

I also don't understand exactly, how you scale input signal respectively how you handle possible overflows when truncating the multiply results. What's nominal full scale signal with your 16.16 format, how do you scale 16 or 24 bit digital audio to it? generally, in a filter, the signal amplitude can appear magnified at some nodes. You have to assure, that the signal isn't truncated with any arbitrary full scale input anyway. Thus some headroom must be granted in signal scaling. On the other hand the said resolution extra could be lost when scaling the input too low.

Regards,

Frank