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Examining articulatory settings using MRI: pilot results

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Gully, A., Foulkes, P., French, J. P., Harrison, P., and Hughes, V. (2019) Examining articulatory settings using MRI: pilot results. Paper presented at the International Association of Forensic Phonetics and Acoustics Conference. Istanbul, Turkey. 14-17 July 2019.

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Examining articulatory settings using MRI: pilot results

  1. 1. Examining articulatory settings using MRI: pilot results Amelia Gully, Paul Foulkes, Peter French, Philip Harrison & Vincent Hughes IAFPA 14-17 July 2019 1
  2. 2. Background – Voice Quality Analysis • Analysis of voice quality common in forensic speaker comparison • E.g. Vocal Profile Analysis (VPA) • Often perceptual analysis only • Aim: establish validity of voice quality analysis Articulation Acoustics Perception 2
  3. 3. Research Questions 1. Do the auditory descriptions (e.g. VPA) match the actual articulation? • E.g. does ‘fronted tongue body orientation’ really involve moving the tongue body forward? 2. Do different speakers use different articulations to produce the same auditory voice quality? 3. What are the acoustic correlates of the different articulatory settings? • Disclaimer: pilot results for 1 speaker, partly addressing Q. 1 3
  4. 4. Methods • In MRI scanner • 2D scans – running speech • Dynamic - video at 4 frames per second • 3D scans – sustained vowels • Simultaneous optical microphone recording • Range of opposing VQs including: • Neutral, fronted tongue, backed tongue, lip rounding, lip spreading… • Produced by trained phoneticians: • Running speech – The North Wind & The Sun • Range of sustained vowels 4
  5. 5. Methods • In anechoic chamber • Complete replication of MRI stimulus • Recorded via • headband microphone • measurement microphone • Laryngograph • mobile phone • Subject lying down • MRI scanner noise via headphones • Range of opposing VQs including: • Neutral, fronted tongue, backed tongue, lip rounding, lip spreading… • Produced by trained phoneticians: • Running speech – The North Wind & The Sun • Range of sustained vowels 5
  6. 6. Limitations • High quality audio recordings are not simultaneous with MRI scans • Effects of gravity from being horizontal • MRI noise Lombard speech • Trained linguists producing range of extreme VQs • Do linguists emulate VQs in the same way that habitual VQs are produced? 6
  7. 7. MRI 2D Scan Output • All speech frames from The North Wind and the Sun • Neutral setting 7
  8. 8. Methods (1) • Manual segmentation of 2D MRI data for running, read speech • Approx. 250ms frames • Multiple articulatory settings 8
  9. 9. Methods (2) • Geometrical feature extraction • Constrictions, heights, fronting • (distances calculated both parallel and perpendicular to “top” and “back” vectors) • LMEM (Linear Mixed Effects Model) comparison with articulatory setting as fixed effect • These results are for a single subject (male) 9
  10. 10. Results • NEUTRAL range of motion → • Results that follow are all compared to neutral setting • Significant effect of settings on: • jaw height and angle • velum and epiglottis tip position • larynx height • pharynx length • protrusion of upper and lower lips • lip aperture • tongue tip and body fronting • pharynx constriction • tongue height “The North wind and the sun were disputing which was the stronger when a traveller came along wrapped in a warm cloak.” 10
  11. 11. “The North wind and the sun were disputing which was the stronger when a traveller came along wrapped in a warm cloak.” Results: tongue fronting • Tongue not fronted? Tip 1.19mm more back Average 1.11mm more back (p<0.005, ±0.37 and 0.29 std.err. respectively) • Jaw lower p<0.0001; 4.12mm ± 0.36 std.err. • Wider jaw angle p<0.0001; 6.7° ± 0.29 std.err. • Lower velum tip p<0.01; 2.24mm ± 0.81 std.err. • No effect on tongue height 11
  12. 12. Results: tongue backing “The North wind and the sun were disputing which was the stronger when a traveller came along wrapped in a warm cloak.” • Tongue more back Tip 2.78mm more back Average 4.41mm more back (p<0.0005, ±0.72 and 0.60 std.err. respectively) • Tongue lower p<0.0001; mean 6.80mm ± 0.51 std.err. • Longer pharynx p<0.0001; 13.69mm ± 0.55 std.err. • Narrower pharynx p<0.0001; 4.48mm ± 0.76 std.err. • Lowered larynx p<0.0001; 16.13mm ± 0.66 std.err. 12
  13. 13. Results: lip rounding “The North wind and the sun were disputing which was the stronger when a traveller came along wrapped in a warm cloak.” • Upper lip more protruding p<0.0001; 2.39mm ± 0.20 std.err. • No significant effect on lower lip? • Tongue more back p<0.001; mean 1.83mm ± 0.56 std.err. • Tongue lower p<0.05; mean 1.47mm ± 0.57 std.err. • Jaw lower p<0.0001; 2.18mm ± 0.37 std.err. 13
  14. 14. Results: lip spreading “The North wind and the sun were disputing which was the stronger when a traveller came along wrapped in a warm cloak.” • Lips less protruding Upper lip 4.58mm less protruding Lower lip 4.16mm less protruding (p<0.0001, ±0.12 and 0.25 std.err. respectively) • Jaw higher p<0.0001; 5.70mm ± 0.34 std.err. • Tongue more back p<0.0001; mean 3.21mm ± 0.43 std.err. • Longer pharynx p<0.0001; 3.41mm ± 0.42 std.err. • Lowered larynx p<0.0001; 3.13mm ± 0.43 std.err. 14
  15. 15. Discussion/Preliminary Conclusions • Clear differences in articulation for each setting • Each setting involves change in relative position of multiple articulators – mostly where expected • Fronted tongue requires more open jaw • Backed tongue requires longer pharynx • Some surprising effects (e.g. for tongue fronting) • May reflect suitability of features • RQ. 1 - Do the auditory descriptions (e.g. VPA) match the actual articulation? • Yes & no – at least for this speaker in these conditions 15
  16. 16. Future work • Tongue shape characterisation (e.g. Principle Component Analysis) • Additional subjects (male and female) • Additional settings (closed/open jaw; raised/lowered larynx) • 3D data (held vowels only) → non-midsagittal and volume features • Acoustic analysis • Variability of parameters • (Semi-) automatic segmentation of MRI images • Determine if different subjects use different strategies to achieve the same goal 16
  17. 17. Thank you for listening! Questions??? IAFPA 14-17 July 2019 17

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