Speech and speaker normalization (in vowel normalization)

1. Speech and speaker normalization (in vowel normalization) Venice International University Phonetic and technological aspects of speaker characteristics Prof. Dr. J. Harrington Presented by Clara Tillmanns clarainindia@yahoo.com 18.10.2007

2. Contents • Speech and speaker normalization in vowel normalization: definition • Influencing parameters and instruments for vowel normalization • Theories • Studies: Johnson 1990 and 1999 • Recapitulation Clara Tillmanns - Speech and speaker normalization

3. Definition Normalization. We know there is extensive variation in speech. How come that listeners agree in their perception of vowels? Clara Tillmanns - Speech and speaker normalization

4. Fig. 1: Scatter plot of first and second formant values of American English vowels. From Peterson & Barney 1952 Clara Tillmanns - Speech and speaker normalization

5. Definition Normalization. Which information influences this decision? Clara Tillmanns - Speech and speaker normalization

6. Definition Normalization. And, which mechanism leads to the decision? Clara Tillmanns - Speech and speaker normalization

7. Contents • Speech and speaker normalization: definition • Influencing parameters and instruments for vowel normalization • Context • Formant ratio • F0 • Visual information • Auditory gestalts • Theories • Studies: Johnson 1990 and 1999 • Recapitulation Clara Tillmanns - Speech and speaker normalization

8. Influencing parameters and instruments for vowel normalization Extrinsic Intrinsic Context Formant ratio F0 Auditory gestalts Visual information Clara Tillmanns - Speech and speaker normalization

9. Influencing parameters and instruments for vowel normalization Syllable internal Syllable external Extrinsic Intrinsic Context Formant ratio F0 Auditory gestalts Visual information Clara Tillmanns - Speech and speaker normalization

10. Influencing parameters and instruments for vowel normalization Syllable internal Syllable external Extrinsic Intrinsic Context Formant ratio Vocalic Prosodic F0 Tonal Auditory gestalts Visual information Clara Tillmanns - Speech and speaker normalization

11. Influencing parameters and instruments for vowel normalization Context: Perceived vowel quality is influenced • by the formant frequencies of context vowels (Ladefoged & Broadbent 1957) • by the F0 range of the carrier phrase (Johnson 1990) Tones: Pitch range of a context utterance influences Mandarin Chinese tones (Leather 1983) Clara Tillmanns - Speech and speaker normalization

12. Influencing parameters and instruments for vowel normalization Syllable internal Syllable external Extrinsic Intrinsic Context Formant ratio Vocalic Relative patterns Prosodic Gender F0 Tonal Auditory gestalts Visual information Clara Tillmanns - Speech and speaker normalization

13. Influencing parameters and instruments for vowel normalization Formant ratio Vowels are relative patterns - no absolute frequencies Clara Tillmanns - Speech and speaker normalization

14. Influencing parameters and instruments for vowel normalization Formant ratio Fig. 2: Spectrogram of a man and a woman saying “cat”. The three lowest vowel formants (vocal tract resonant frequencies are marked as F1, F2 and F3) (Johnson 2004) Clara Tillmanns - Speech and speaker normalization

15. Influencing parameters and instruments for vowel normalization F0 Miller 1953 doubled F0 and found vowel category shift for most American English vowels Fujisaki & Kawashime 1968: Found F1 boundary shifts from 100Hz to 200Hz for F0 shifts of 200Hz Clara Tillmanns - Speech and speaker normalization

16. Influencing parameters and instruments for vowel normalization Syllable internal Syllable external Extrinsic Intrinsic Context Formant ratio Vocalic Relative patterns Prosodic Gender F0 Tonal Auditory gestalts Visual information Articulatory gestures Gender / Age Clara Tillmanns - Speech and speaker normalization

17. Influencing parameters and instruments for vowel normalization Visual information • Gender: boundary shift much like the F0 shift (Strand & Johnson 1996) • Age • Vowel quality: boundary shift through differing visual phonetic information (Johnson 1999) • Sociocultural: Speech intelligibility is reduced, when the voice is associated with an Asian looking face (Rubin 1992) Clara Tillmanns - Speech and speaker normalization

18. Influencing parameters and instruments for vowel normalization Auditory gestalts - “secondary cues” Duration Formant frequency movement trajectories: • Lehiste & Metzger 1973: • Fixed duration vowels synthesized with steady-state formant frequencies (51% correct) - mixed lists of the original vowels from men, women and children 79% correct. • Hillenbrand & Neary 1999: • Flat-formant vowels were correctly identified 74% of the time, while vowels synthesized with the original formant frequency trajectories were correctly identified 89% of the time. Clara Tillmanns - Speech and speaker normalization

19. Contents • Speech and speaker normalization in vowel normalization: definition • Influencing parameters and instruments for vowel normalization • Theories 3.1 Vocal tract normalization (VTN) 3.2 Talker normalization (TN) 4. Studies: Johnson 1990 and 1999 5. Recapitulation Clara Tillmanns - Speech and speaker normalization

20. Theories - VTN Vocal tract normalization theories consider that listeners perceptually evaluate vowels on a talker specific coordinate system.” (Johnson 2004) • Context vowels (reference) • Visual information about the size of the vocal tract Clara Tillmanns - Speech and speaker normalization

21. Theories - VTN But: Talkers may differ from each other at the level of their articulatory habits of speech: “Perception may not be able to depend on vocal tract normalization to “remove” talker differences by removing vocal tract differences.” (Johnson 2004)  Speaker/speech variation depends on anatomical differences only? Clara Tillmanns - Speech and speaker normalization

22. Theories - VTN Cross-linguistic gender differences Bladon, Henton and Pickering (1984): The difference between men and women vary from language to language. • Cultural factors are involved in defining and shaping male or female speech • Anatomy does not completely determine the vowel formant frequencies Clara Tillmanns - Speech and speaker normalization

23. Theories - VTN Fig. 3 Spectral shift needed to normalize male and female spectra From Bladon, Henton & Pickering (1984) Clara Tillmanns - Speech and speaker normalization

24. Theories - VTN “This seems to suggest that talkers choose different styles of speaking as social, dialectal gender markers. A speaker normalization that removes vocal tract differences will fail to account for the linguistic categorical similarity of vowels that are different due to different habits of articulation.” (Johnson 2004) Clara Tillmanns - Speech and speaker normalization

25. Theories - TN Talker normalization is subject to expectations: Magnuson & Nusbaum (1994) compared 1-voice with 2-voice instructions in a mixed-talker and blocked-talker experiment. Advantage of blocked-talker disappeared when subjects didn’t know about the different F0s of the two voices. Talker normalization is an active process: Kato & Kakehi (1988) Listener adaptation to talker voice: Increase in recognition accuracy over the course of 5 stimuli presented in noise Clara Tillmanns - Speech and speaker normalization

26. Theories - TN “In this approach, cognitive categories are represented as collections of the stored cognitive representations of experienced instances of the category, rather than as normalized abstract representations from which category-internal structure has been removed” (Johnson 2004) Clara Tillmanns - Speech and speaker normalization

27. Contents • Speech and speaker normalization in vowel normalization: definition • Influencing parameters and instruments for vowel normalization • Theories • Studies 4.1 Johnson 1990 4.2 Johnson 1999 5. Recapitulation Clara Tillmanns - Speech and speaker normalization

28. Studies “The role of perceived speaker identity in F0 normalization of vowels” (Johnson 1990) Presentation of vowels from a “hood”-”hud” continuum in two different intonational contexts which were judged to have been produced by different speakers, even though the F0 of the test word was identical in the two contexts. Clara Tillmanns - Speech and speaker normalization

29. Studies “The role of perceived speaker identity in F0 normalization of vowels” (Johnson 1990) • Shift in identification as a result of the intonational context • which was interpreted as evidence for the role of perceived speaker identity in vowel normalization Clara Tillmanns - Speech and speaker normalization

30. Studies “Auditory-visual integration of talker gender in vowel perception” (Johnson 1999) Exp. 1 found, that the gender of auditory-visually presented stimuli shift the phoneme boundary of a vowel continuum Exp. 2 found that visual phonetic information is integrated in the boundary shift Exp. 3 showed that listeners integrate abstract gender information with phonetic information in speech perception Clara Tillmanns - Speech and speaker normalization

31. Contents • Speech and speaker normalization in vowel normalization: definition • Influencing parameters and instruments for vowel normalization • Theories • Studies: Johnson 1990 and 1999 • Recapitulation Clara Tillmanns - Speech and speaker normalization

32. Recapitulation • Great internal and external influence on the perception (of vowels) • Explanation must integrate repeated learning • Information on speaker identity influences the perception (of vowels) • But: Is the perception of speaker identity influenced by certain components of the speech signal? • May speaker identity be manipulated? Clara Tillmanns - Speech and speaker normalization

33. References Bladon, R.A., Henton, C. G. & Pickering, J. B. (1984) Towards an auditory theory of speaker normalization. Language Communication 4, 59-69. Fujisaki, H. & Kawashima, T. (1968) The roles of pitch and higher formants in the perception of vowels. IEEE Transactions on Audio and Electroacoustics AU-16, 73-77. Hillenbrand, J. M. & Neary, T. M. (1999) Identification of synthesized /hVd/ utterances: Effects of formant contour. J. Acoust. Soc. Am. 105, 3509-3523. Ladefoged, P. & Broadbent, D. E. (1957) Information conveyed by vowels. J. Acoust. Soc. Am. 29, 98-104 Leather, J. (1983) Speaker normalization in the perception of lexical tone. Journal of Phonetics 11, 373-382 Lehiste, I. & Metzger, D. (1973) Vowel and speaker identification in natural and synthetic speech. Language and Speech 16, 356-364. Johnson, K., Strand, E. A. & D’Imperio, M. (1999) Auditory-visual integration of talker gender in vowel perception. Journal of Phonetics 27, 359-384 Johnson, K. (2004) Speaker normalization in speech perception. Ohio State University Johnson, K. (1990) The role of percieved speaker identity in F0 normalization of vowels. J. Acoust. Soc. Am. 88 642-654 Kato, K & Kakehi, K. (1988) Listener adaptability to individual speaker differences in monosyllabic speech perception. J. Acoust. Soc. Of Japan 44, 180-186 Magnuson, J. & Nusbaum, H. (1994) Are representations used for talker identification available for talker normalization? Proceedings of the International Conference on Spoken Language Processing. Miller, R. L. (1953) Auditory tests with synthetic vowels. J. Acoust. Soc. Am. 25, 114-121. Peterson, G. E. & Barney, H. L. (1952) Control methods used in the study of vowels. J. Acoust. Soc. Am. 24, 175-184 Rubin, D. L. (1992) Non-language factors affecting undergraduates’ jedgements of non-native English-speaking teaching assistants. Research in Higher Education 33, 4. Strand, E. A. & Johnson, K. (1996) Gradient and visual speaker normalization in the perception of fricatives. In Natural languag processing and speech technology: results of the 3rd KONVENS conference, Bielefeld, (D. Gibbon, Ed.), Berlin: Mouton de Gruyter (pp. 14-26). Clara Tillmanns - Speech and speaker normalization