Pitch Manipulation with Phase Vocoding

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Pitch Manipulation with Phase Vocoding
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The Voder

• Dudley 1928
• Speech comprises slowly modulated periodic and
  aperiodic signals
• Transmit low freq modulations and re-create
  using pulses (periodic) / noise (aperiodic)

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"At the 1939 World's Fair a machine called a
Voder was shown . A girl stroked its keys and it
emitted recognsable speech. No human vocal cords
entered into the procedure at any point the keys
simply combined some electronically produced
vibrations and passed these on to a
loud-speaker." ("As We May Think" by Vannevar
Bush, 1945. )
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Heres the science!

• Analysis Synthesis
• Input -gt Bandpass filters
• Filters are binsfor freqs across the spectra
  (1/2 Nyquist)
• Can alter no. bins and fourier windows
• Scaling and reconstruction

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Examples

• Varying parameters -gt trade-off frequency
  smear and resolution

..\Studio Work\Vocoder
http//www.panix.com/jens/pvoc-dolson.par
http//eamusic.dartmouth.edu/book/MATCpages/chap.
5/5.4.pvoc.html
Elements of Computer Music (Moore)