CENTER FOR SPOKEN LANGUAGE UNDERSTANDING 1

PREDICTION AND SYNTHESIS OF PROSODIC EFFECTS ON SPECTRAL

BALANCE OF VOWELS

Jan P.H. van Santen and Xiaochuan Niu

Center for Spoken Language UnderstandingOGI School of Science & Technology at OHSU

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OVERVIEW

1. IMPORTANCE OF SPECTRAL BALANCE2. MEASUREMENT OF SPECTRAL BALANCE3. ANALYSIS METHODS4. RESULTS5. SYNTHESIS6. CONCLUSIONS

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1. IMPORTANCE OF SPECTRAL BALANCE

• Linguistic Control Factors– Stress-like factors– Positional factors– Phonemic factors

• Acoustic Correlates– Traditionally TTS-controlled:

• Pitch, timing, amplitude

– Demonstrated in natural speech, but usually not TTS-controlled:• Spectral tilt, balance• Formant dynamics• …

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2. MEASUREMENT OF SPECTRAL BALANCE

• Data:– 472 greedily selected sentences

• Genre: newspaper• Greedy features: linguistic control factors

– One female speaker– Manual segmentation– Accent: independent rating by 3 judges

• 0-3 score

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2. MEASUREMENT OF SPECTRAL BALANCE

• Energy in 5 formant-range frequency bands– B0: 100-300 Hz [~F0]

– B1: 300-800 Hz [~F1]

– B2: 800-2500 Hz [~F2]

– B3: 2500-3500 Hz [~F3]

– B4: 3500- max Hz [~fricative noise]

• In other words, multidimensional measure• Filter bank Square

Average [1 ms rect.] 20 log10(Bi )

• Subtract estimated per-utterance means

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2. MEASUREMENT OF SPECTRAL BALANCE

• Details:– Confounding with F0

• Measure pitch-corrected and raw– For certain wave shapes, pitch directly related to fixed-frame

energy– Why do both: wave shapes may change in unknown ways

• F0 not confined to B0 [female speech]

– Vowel formants not quite confined to bands [e.g., F1 for /EE/ and F3 for /ER/]

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2. MEASUREMENT OF SPECTRAL BALANCE

• Why not more or different bands?– Multiple interacting Linguistic Control Factors

• Need measurements that minimize interactions

– 5 bands Different vowels “behave similarly”• Can model vowels as a class

• Why not simply spectral tilt?– 5 bands more information than single measure– Supply more information for synthesis

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3. ANALYSIS METHODS

• Measures likely to behave like segmental duration:– Multiple interacting, confounded factors:

• Interaction: Magnitude of effects on one factor may depend on other factors

• Confounding: Unequal frequencies of control factor combinations

– “Directional Invariance”• Direction of effects on one factor

independent of other factors

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3. ANALYSIS METHODS

• Need method that – can handle multiple interacting,

confounded factors and – takes advantage of Directional

Invariance:

• Used: Sums of Products Model:

Ki Ij

jjini

i

cSccB )(),...,( ,0

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3. ANALYSIS METHODS

• Special cases:– Multiplicative model: K = {1}, I1 = {0,…,n}

)()(),...,( ,100,10 nnni cScSccB

)()(),...,( 1,01,00 nnni cScSccB

– Additive model: K = {0,…,n}, Ii = {i}

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3. ANALYSIS METHODS

• Used additive model

• Note: Parameter estimates are:– Estimates of marginal means …– … in balanced design:

),...,,...,()( 0,...,,...,

1,00

niiCcccCc

ii cccBMeancSnnii

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3. ANALYSIS METHODS

• Pitch correction:

)(log20)(log20 10010][

wici tfBB

• Confounding with F0: Show both

<B0, B1, B2, B3, B4> and:

<B0 + B1, B2, B3, B4>

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4. RESULTS: (A) POSITIONAL EFFECTS

5 Bands, not pitch-correctedSolid: right position, dashed: left position. Y-axis: corrected mean

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4. RESULTS: (A) POSITIONAL EFFECTS

5 Bands, pitch-corrected

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4. RESULTS: (A) POSITIONAL EFFECTS

4 Bands, not pitch-corrected

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4. RESULTS: (A) POSITIONAL EFFECTS

4 Bands, pitch-corrected

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4. RESULTS: (B) STRESS/ACCENT EFFECTS

5 Bands, not pitch-correctedSolid: stressed syllable, dashed: unstressed. Y-axis: corrected mean

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4. RESULTS: (B) STRESS/ACCENT EFFECTS

5 Bands, pitch-corrected

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4. RESULTS: (B) STRESS/ACCENT EFFECTS

4 Bands, not pitch-corrected

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4. RESULTS: (B) STRESS/ACCENT EFFECTS

4 Bands, pitch-corrected

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4. RESULTS: (C) TILT EFFECTS

4

3

2

1

0

)2,1,0,1,2(

B

B

B

B

B

Tilt

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5. SYNTHESIS

• Use ABS/OLA sinusoidal model:s[n] = sum of overlapped short-time signal frames sk[n]

sk[n] = sum of quasi-harmonic sinusoidal components:

sk[n] lAk,l cos(k,l n + k,l

• Each frame of unit is represented by a set of quasi-harmonic sinusoidal parameters;

• Given the desired F0 contour, pitch shift is applied to the sinusoidal parameter component of the unit to obtain the target parameter Ak,l ;

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5. SYNTHESIS

• Considering the differences of prosody factors between original and target unit, band differences:

iii BB ˆ

• Transform the band difference into weights applying to the sinusoidal parameters:

i

2010 iiw

• ,when the j’th harmonic is located in

the i'th band;ikjkj wAA

• Spectral smoothing across unit boundaries.

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5. SYNTHESIS

5 Bands modification example [i:]

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CONCLUSIONS

• Described simple methods for predicting and synthesizing spectral balance

• But: Spectral balance is only one “non-standard acoustic correlate”

• Others that remain to be addressed:– Spectral dynamics– Phase