1. Analog and Digital Filters used in Audio Contexts Tufts University – ME 93 October 22, 2015

2. Outline Where do we use filters? History of filters How do filters do what they do? What types of filters do we use? What are the advantages and disadvantages of each?

3. Where do we use filters? ADC/DAC Equalizers Filter based effects

6. History of Filters

8. Fixed Frequencies 1971 = Parametric EQ Movable frequencies Adjustable bandwidth

9. Types of Simple Filters High/Low Pass Shelving Filters Band pass/band reject

10. Digital IIR Infinite Impulse Response filter Non-linear Delay elements are added to create phase shift Often emulated using convolution

11. Digital FIR Finite Impulse Response filter Can achieve linear phase response but adds ‘ringing’

12. What’s this sound like?

13. Next Steps Will Pirkle: Designing Audio Effects Plug-ins in C++ Musicdsp.org Kvraudio.com DSP & Plug-in development forum CCRMA Web Audio School