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Vowel Acoustics, part 2

Vowel Acoustics, part 2. November 14, 2012. The Master Plan. Acoustics Homeworks are due! Today: Source/Filter Theory On Friday: Transcription of Quantity/More Vowels of the World There’s also another production exercise due next Wednesday! Production of exotic vowels

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Vowel Acoustics, part 2

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  1. Vowel Acoustics, part 2 November 14, 2012

  2. The Master Plan • Acoustics Homeworks are due! • Today: • Source/Filter Theory • On Friday: • Transcription of Quantity/More Vowels of the World • There’s also another production exercise due next Wednesday! • Production of exotic vowels • Measure your own vowel formants!

  3. Vowel Acoustics • Vowels are primarily distinguished by their first two formant frequencies: F1 and F2 • F1 corresponds to vowel height: • lower F1 = higher vowel • higher F1 = lower vowel • F2 corresponds to front/backness: • higher F2 = fronter vowel • lower F2 = backer vowel • Also: lip rounding tends to lower both formants. • A caveat: rounded vowels (like [u] and [o]) are often fronted in modern English.

  4. “Normalcy” “booed” “bode”

  5. Feeling Minnesota “booed” “bode”

  6. Looking California “booed” “bode”

  7. Vowel Diacritics • The IPA contains a few diacritics which are especially relevant to vowels. • The most important of these is the diacritic for nasalization. • Ex: = nasalized [e] • Nasalized vowels are produced by lowering the velum during the production of a vowel • air flows through both the nose and the mouth • Contrastive nasal vowels are found in  20% of the world’s languages

  8. Back to French

  9. Nasal Vowel Acoustics • The acoustics of nasal vowels are very complex. • One general pattern: nasalization expands bandwidths. • this smears formants Chinantec Examples

  10. Nasal Vowel Acoustics • Nasalization smears vowel bandwidths, which can obscure F1 (vowel height) differences • high vowels sound low • low vowels sound high • Note: American English “pen” vs. “pin” • French: [le] vs. • [lo] vs.

  11. Nasal Spreading • Nasalization often spreads from consonants to vowels • Sundanese (spoken in Indonesia) has a famous pattern of nasal spreading, which is blocked by certain consonants.

  12. http://www.kayelemetrics.com/Product%20Info/6400/6400.htm Nasometer • A tool which has been developed for studying the nasalization of vowels (and other segments) is the Nasometer. • The Nasometer uses two microphones to measure airflow through both the mouth and nose at the same time.

  13. More Nasometer • The Nasometer spits out readings of the amount of air flowing out of the nose and the mouth at the same time. • nasal vowels: concomitant airflow through both mouth and nose • nasal stops: airflow only through nose

  14. 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

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

  16. 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.

  17. “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.

  18. Source + Filter = Output + =

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

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

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

  22. at different pitches 100 Hz 120 Hz 150 Hz

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

  24. 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

  25. 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

  26. 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)

  27. 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.

  28. 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.

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

  30. Women and Men • The acoustics of male and female vowels differ reliably along two different dimensions: • Sound Source • Sound Filter • Source--F0: depends on length of vocal folds • shorter in women  higher average F0 • longer in men  lower average F0 • Filter--Formants: depend on length of vocal tract • shorter in women  higher formant frequencies • longer in men  lower formant frequencies

  31. [i] [u] [æ]

  32. [i] [u] [æ]

  33. Prototypical Voices • Andre the Giant: (very) low F0, low formant frequencies • Goldie Hawn: high F0, high formant frequencies

  34. F0/Formant mismatches • The fact that source and filter characteristics are independent of each other… • means that there can sometimes be source and filter “mismatches” in men and women. • What would high F0 combined with low formant frequencies sound like? • Answer: Julia Child.

  35. F0/Formant mismatches • Another high F0, low formants example: • Roy Forbes, of Roy’s Record Room (on CKUA 93.7 FM) • The opposite mis-match = • Popeye: low F0, high formant frequencies

  36. In Conclusion • Everybody’s vowel space is different. • A vowel space is defined by a speaker’s range of first formant (F1) and second formant (F2) frequencies. • We identify vowels on the basis of the patterns formed by their formants within that acoustic space. • F1 determines the height of vowels. • F2 determines the front/backness of vowels. • Questions?

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