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Exam 1997 Question 7

"Outline the principles behind spectrographic analysis, discussing why both wide and narrow band filters are used to study speech signals. Contrast the filters used in the spectrograph to analyse speech with those supposed to operate in the cochlea."

20 things you should mention:

  • Spectrography
    • time axis
    • freq axis
    • amplitude as shades of grey
    • consider as bank of filters
    • constant spacing
    • constant bandwidth
    • Narrow = 45 Hz
    • shows harmonics
    • info about Fx
    • good frequency resolution
    • Wide = 300Hz
    • shows striations
    • and formant damping
    • info about formant freqs.
    • good temporal resolution
  • Cochlea
    • arise from masking effects
    • not constant bandwidth
    • narrow at low, wide at high
    • not constant spacing
    • closer at low, further apart at high

© 2000 Mark Huckvale University College London