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Vowels, part 4

Vowels, part 4. March 19, 2014. Just So You Know. Today: Source-Filter Theory For Friday: vowel transcription! Turkish, British English and New Zealand English For next Wednesday: Production Exercise #3 (on Vowels, natch) Formant Measuring Exercise. The Great Lakes Shift.

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Vowels, part 4

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  1. Vowels, part 4 March 19, 2014

  2. Just So You Know • Today: Source-Filter Theory • For Friday: vowel transcription! • Turkish, British English and New Zealand English • For next Wednesday: • Production Exercise #3 (on Vowels, natch) • Formant Measuring Exercise

  3. The Great Lakes Shift • One chain shift is currently taking place in the northern United States. • Prevalent in Chicago, Detroit, Cleveland, Buffalo, and many places in between • (but not in Toronto) • (but maybe in Windsor!) • GeneralGreat Lakes

  4. fronting

  5. [æ] raising

  6. backing “ahead”

  7. Female Talkers

  8. Female Talkers

  9. New Zealand Vowel Shift http://www.youtube.com/watch?v=JT5AQIlmM0I

  10. A Word of Caution • The vowel system of English can vary greatly from one dialect to another. • Ex: the vowels of Canadian English have shifted away from their American counterparts… • (for some, but not all, speakers) • Shift #1:  Unshifted: Unshifted: • Shift #2:  • There are also new shifts underway! • Shift #3:  “head” • Shift #4:  “hid” • Shift #5:  “hood”

  11. Source/Filter Theory: The Source • Developed by Gunnar Fant (1960) • For speech, the source of sound = complex waves created by periodic opening and closing of the vocal folds

  12. Source Differences adult male voice (F0 = 150 Hz) child voice (F0 = 300 Hz)

  13. Just So You Know • Voicing, on its own, would sound like a low-pitched buzz. • Check out the sawtooth wave spectrum: • Vowels don’t sound like this because the source wave gets “filtered” by the vocal tract.

  14. “Filters” • For any particular vocal tract configuration, certain frequencies will resonate, while others will be damped. • analogy: natural variation/environmental selection • This graph represents how much the vocal tract would resonate for sinewaves at every possible frequency.

  15. Source + Filter = Output + =

  16. A Vowel Spectrum F1 F2 F4 F3 Note: F0  160 Hz

  17. Output Example: [i] • Different vowels are characterized by different formant frequencies. • These reflect changes in the shape of the sound filter. • (the vocal tract)

  18. Vowel Spectrum #2: [i] F1 F3 F2 F0 = 185 Hz

  19. at different pitches 100 Hz 120 Hz 150 Hz

  20. Narrow-Band Spectrogram • A “narrow-band spectrogram” clearly shows the harmonics of speech sounds. • …but the formants are less distinct. harmonics

  21. Wide-Band Spectrogram • By changing the parameters of the Fourier analysis, we can get a “wide-band spectrogram” • This shows the formants better than the harmonics. formants

  22. Wide-Band Spectrogram • By changing the parameters of the Fourier analysis, we can get a “wide-band spectrogram” • This shows the formants better than the harmonics. F3 formants F2 F1

  23. Wide-Band Spectrogram • By changing the parameters of the Fourier analysis, we can get a “wide-band spectrogram” • This shows the formants better than the harmonics. F3 formants F2 F1 voice bars (glottal pulses)

  24. Spectrographically • This is what it looks like when you change the source independently of the filter. • The formants stay the same, but the F0 and harmonics change.

  25. The Flip Side • This is what it looks like when you change the filter independently of the source. • The resonating frequencies change, but the F0 and harmonics stay the same.

  26. More Relevantly • In diphthongs, the filter changes while the source can remain at the same F0. “Boyd” • Check out the narrow-band spectrogram…

  27. More Music • With (most) musical instruments, we can only change the frequency of the sound source. • Timbre is a musical term for the “quality” of a sound. • I.e., its characteristic resonances. • E.g., compare the same note played by a trumpet vs. a violin. • In speech, you can independently change both source and filter frequencies at the same time. • Like changing the size of a piano… • As you press different keys on the keyboard. • This makes the acoustics of speech at least twice as complex as the acoustics of music.

  28. Formant-Reading Tip #1 • Another distinction between source and filter characteristics is formant bandwidth. • Harmonics are exact: • integer multiples of source frequency • Resonances are less exact: • they’re centered around an optimal frequency, but other frequencies may resonate to some extent, too. • Hence: formants can appear to merge in wide-band spectrograms.

  29. Bandwidth

  30. Bandwidth

  31. Merged Formants F2 F1

  32. Another Problem: Dynamics F2 F2 F1 F1 “hod” • vowel formants are typically not “steady-state” for very long

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