I’ve been thinking about adding a custom notch filter to Asterisk somehow to filter out / attenuate specific frequencies (e.g. 2600 Hz). It seems like the most efficient way to do this would be using Goertzel, just like the DTMF and MF filters in dsp.c do. goertzel_init seems to be promising. I’m not sure what the best way would be to have this set with a function - I’m thinking similar to how you can do Set(VOLUME(TX)=-5) or Set(MUTEAUDIO(in)=on), something like SET(NOTCH_FILTER(2600)=on) or SET(NOTCH_FILTER(2600)=4) (to control the attenuation). When I look at examples of new DSPs being created though, it’s all in the context of applications which are blocking, such as creating a new DSP for silence detection and then releasing it. I’d want this to be active for the duration of the call. I’m wondering if anyone has thoughts on the optimal way this might be architected. Thanks!