1. Feedback Filters n A feedback filter processes past output samples, as well as current input samples: n Feedback filters create peaks (poles or resonances) in the spectrum of their output. n Feedback filters are also called resonant filters or recursive filters. Frequency response/

2. Lowpass Filters Feedforward Cutoff frequency oscillates between 400 Hz and 4000 Hz Feedback White noise

3. Lowpass Filters Feedforward Cutoff frequency oscillates between 400 Hz and 4000 Hz Feedback Sawtooth wave

4. A Feedforward Highpass Filter Simple HPF - white noise Cutoff frequency oscillates: 400 - 4000 Hz Duration: 7.5 sec Range: 0 - 6 kHz Simple HPF - sawtooth Cutoff frequency oscillates: 400 - 4000 Hz Duration: 7.5 sec Range: 0 - 6 kHz

5. Feedback Highpass Filter n A feedback filter performs multiplications on samples that it has output, as well as samples that are input to it: Frequency response/

6. Feedback Highpass Filter Resonant HPF - white noise Cutoff frequency oscillates between 400 - 4000 Hz Note the spectral peak (dark band) at the cutoff frequency Range: 0 - 10 kHz Duration: 7.5 seconds Resonant HPF - sawtooth Cutoff frequency oscillates between 400 - 4000 Hz Note the spectral peak (dark band) at the cutoff frequency Range: 0 - 6 kHz Duration: 7.5 seconds

7. Bandpass Filter n Bandpass filters are typically feedback filters—also called resonz, since they resonate at a center frequency.

8. Bandpass Filter n Bandpass filters are typically feedback filters—also called resonz, since they resonate at a center frequency. n It is difficult to do this degree of spectral shaping with feedforward filters.

9. Bandpass Filter n Bandpass filters are typically feedback filters—also called resonz, since they resonate at a center frequency. n It is difficult to do this degree of spectral shaping with feedforward filters. n Bandpass filters are covered in the presentation Feedforward Filtering.