ep-4yy13 DSP – week 7

frequency domain

transforming signals

  • DFT, FFT, STFT
  • The FFT produces a stream of complex numbers representing energy at frequencies across the spectrum
  • The length of the FFT determines the frequency resolution (number of bins)
  • Increasing length of FFT frame degrades resolution in time domain (rhythmic accuracy)
  • Amplitude = root of (r*r) + (i*i)  = magnitude
  • Phase = arctangent of i/r = angle

Practical Applications

  • Convolution/Deconvolution
  • Analysis
  • Spectral processing (pitch and timbre)
  • Amplitude processing: noise gates, crossovers
  • phase vocoder
  • radio

Examples

  • Max/MSP tutorials 25-26
  • Max/MSP Example DSP patches (in Extras | ExamplesOverview | MSP | FFT fun
    • convolution workshop
    • Forbidden planet
  • Fourier Filter (Vetter)
  • fft-tz2 (basics, SSB ring modulator)
  • fplanet-tz.maxpat: hacked version of forbidden-planet example which uses granular indexing to do spectral convolution and make spaceship sounds. To use patch: 1 ) turn on audio, 2) then press message boxes inside the green panel
  • fp-fft-tz.maxpat: pfft~ subpatch for above
  • fourierfilter (folder) containing fourierfiltertest.maxpat: Katja Vetter’s complex spectral filter example
  • Tristan Jehan’s frequency detector object
  • Little Tikes piano: https://reactivemusic.net/?p=6993
  • Helicopter frame rate video: http://www.youtube.com/watch?v=jQDjJRYmeWg
download example Max patches here:
Resources

Assignments

See notes from previous weeks: https://reactivemusic.net/?p=10109