This document analyzes, models, and synthesizes British, Australian, and American accents. It discusses the acoustic differences between accents, including differences in phonetic transcriptions and realizations, as well as prosodic correlates like formants, pitch, duration, and voice quality. The document then describes methods for accent analysis using tools like HMMs, formant tracking, and pitch estimation. It also presents techniques for accent morphing through formant and prosody modification to transform a source accent into a target one.

1. Analysis, Modelling and Synthesis of British, Australian and American Accents Qin Yan Saeed Vaseghi Multimedia Communication Signal processing Lab Department of Electronic and Computer Engineering Brunel University Supported by EPSRC

7. (b) Pitch prosody correlates of accents, include : (i) Pitch trajectory at various linguistic contexts and positions . e.g. pitch rise, at the beginning of a voiced group or phrase, pitch fall at the end of a phrase . (ii) Pitch nucleus i.e. the timing and magnitude of the prominent pitch event in a voiced group. (c) Duration and Timing correlates of accents, (i) Duration of vowels and dip h thongs . (ii) Relative duration and timings of the two constituent vowels of dip h thongs. (d) Laryngeal (glottal) correlates of accents , i.e the voice quality of speech segments in certain contexts as a function of accent .

9. Accent Profile (AP) Parameters Comments Rank Phonetic Parameters Substitution, insertion, deletion Pronunciation differences obtained from phonetic transcription dictionaries ***** Supra-laryngeal and Laryngeal Correlates Formants & their trajectories 2 nd formant with largest variance is most sensitive to accent **** Glottal pulse (Voice Quality) Durations and shapes of opening and closing of glottal folds ** Prosody Correlates F 0 mean Average of pitch * F 0 range Range of pitch * Pitch Nucleus Prominent point (stressed) within an intonation group (Tone Unit) *** Initial Pitch Rise First pitch slope of a narrative utterance *** Final Pitch Lowering Final fall pitch slope of a narrative utterance *** Final Pitch Rise Final rise pitch slope of a narrative utterance *** Timing and Delivery Correlates Speaking Rate Phonemes or words per second * Phoneme Duration Vowel duration elongation and complete pronunciation all affect *** Excessive Co-articulation Clipped or short duration sounds ****

11. Analysis of Duration Correlate of AU, US and UK Accent Speech Figure: Comparison of s peaking rates of British, Australian and American. Figure: Comparison of phoneme durations of British, Australian and American. 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 aa ae ah ao aw ay eh er ey ih iy ow oy uh uw Australian British American Duration (sec)

15. Three spectrogram examples of formant tracks superimposed on LPC spectrum of speech

16. Comparison of histograms (thin solid line) and Gaussian HMMs of formants of Australian English (bold dashed line). X axis: frequency (Hz); Y axis: probability. The figures show that HMMS are excellent models of the distribution of the formants.

18. Figure : Comparison of trajectories and target time of formant of British, Australian and American accents

21. Formant Transformation via Non-Uniform LP Frequency Warping Figure Illustration of a non-uniform frequency warping using LP model frequency response. The spectrum is divided into a number of bands centered on the formants and a different set of warping parameters is applied to each band. F 01 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 -75 -70 -65 -60 -55 -50 -45 -40 -35 F 12 F 23 F 34 F 45 BW 1 BW 2 BW 3 BW 4 I 12 I 23 I 34 Magnitude (dB) Frequency (Hz) Figure : Illustration modification of spectrum towards formants of target accent Speech Linear Prediction Model LP Spectrum Mapping Formant Estimation Formant Transformation Ratios Accent modified spectrum Formant HMMs Polynomial roots Pole estimation

22. The frequency bands of the source speaker [ F 01 F 12 F 23 F 34 F 45 ] are mapped to the target accent using a set of warping ratios derived from differences in the formants of phonetic segments of speech across accents as ) 1 ( ) 1 ( ) 1 (     i i i i i i f f  S i S i T i T i i i f f f f       1 1 ) 1 (  Where f i T and f i S are the i th formants of the source and target accents The frequency mapping can be expressed as Figure : Illustration of warped(solid line) and original(dash dot line) formant trajectories of /aa/ in accent conversion from Australian to British.

24. Examples of changes in accent/duration modulation of pitch (a) ‘article’ in Australian, (b) Australian-accent ‘article’ transformed to British accent (c) ‘asked’ in Australian, (d) Australian-accent ‘article’ transformed to British accent (a) (b) (c) (d)

25. Model Estimation LP Model Formant Trajectory Source Speech Target Speech LP Model Formant Trajectory Mapped Speech Warping Factors Target Speaker HMM Model Source Speaker HMM Model Formant Tracking Formant Mapping Speech Recon struction Speech Reconstruction LPC - Spectrum Warping / Pole Rotation Model Estimation LP Model Formant Trajectory Source Speech Target Speech LP Model Formant Trajectory Mapped Speech Warping Factors Target Speaker HMM Model Source Speaker HMM Model Formant Tracking Formant Mapping Speech Recon - struction Speech Reconstruction LPC - Spectrum Warping / Pole Rotation Transformed(AM m->f) American male American female An Outline of Voice-Morph: A system for Voice and Accent Conversion An example of voice conversion

26. Accent Conversion Demonstration Australian British Transformed British American Transformed ‘ Article’ ‘ Claim’ ‘ Cooperation ’ ‘ Beige’ Source Accent Target Accent Spoken word ‘ Boston’ ‘ Opposition’ ‘ The occupied’

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