Analog and Digital Filters used in Audio ContextsTufts University – ME 93October 22, 2015

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?

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

History of Filters

History of Filters

History of Filters• Fixed Frequencies• 1971 = Parametric EQ• Movable frequencies• Adjustable bandwidth

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

DigitalIIR• Infinite Impulse Response filter• Non-linear• Delay elements are added to create

phase shift• Often emulated using convolution

DigitalFIR• Finite Impulse Response filter• Can achieve linear phase response but

adds ‘ringing’

What’s this sound like?

Next Steps• Will Pirkle:

Designing Audio Effects Plug-ins in C++• Musicdsp.org

Kvraudio.com DSP & Plug-in development forum• CCRMA• Web Audio School