Laryngeal Function and Speech Production

1. Laryngeal Function and Speech Production

2. Learning Objectives • Describe the basic role of the larynx in speech and song.

3. What is the basic role of the larynx in speech and song • Sound source to excite the vocal tract • Voice • Whisper • Prosody • Fundamental frequency (F0) variation • Amplitude variation • Realization of phonetic goals • Voicing • Devoicing • Glottal frication (//, //) • Glottal stop (//) • Aspiration • Para-linguistic and extra-linguistic roles • Transmit affect • Speaker identity

4. Learning Objectives • Possess a knowledge of laryngeal anatomy sufficient to understand the biomechanics, aerodynamics and acoustics of phonation.

5. The hyo-laryngeal complex SPPA 4030 Speech Science

6. Extrinsic/Supplementary Muscles SPPA 4030 Speech Science

7. Intrinsic muscles SPPA 4030 Speech Science

8. Muscular Actions SPPA 4030 Speech Science

9. CA joint function SPPA 4030 Speech Science

10. Muscular actions on vocal folds • Alter position • Adduction • LCA, IA, TA • Abduction • PCA • Alter tension (and length) • Increase/decrease longitudinal tension • Balance between TA and CT SPPA 4030 Speech Science

11. Extrinsic/supplementary muscles • Holds the larynx in the neck • Allows positional change of the larynx • Elevates when swallowing • Elevates during certain speech activities • Elevating pitch • High vowel production SPPA 4030 Speech Science

12. The larynx SPPA 4030 Speech Science

13. “Layered” structure of vocal fold SPPA 4030 Speech Science

14. Basic Structure of the vocal fold • epithelium • connective tissue • superficial layer • tissue loosely connected to the other layers • intermediate layer • elastic fibers • deep layer • collagen fibers (not stretchy) • muscle (TA) Lamina propria Vocal ligament SPPA 4030 Speech Science

15. Newborns No layered structure of LP LP loose and pliable Children Vocal ligament appears 1-4 yrs 3-layered LP is not clear until 15 yrs Old age Superficial layer becomes edematous & thicker Thinning of intermediate layer and thickening of deep layer Changes in LP more pronounced in men Muscle atrophy The vocal fold through life…

16. Learning Objectives • Describe the control variables of laryngeal function.

17. Laryngeal Opposing Pressure • Pressure that opposes translaryngeal air pressure • Sources • Muscular pressure • Surface tension • Gravity

18. Laryngeal Airway Resistance (LAR) • Components of LAR • Translaryngeal pressure • Translaryngeal flow • Values can vary widely Resistance=Pressure/Flow

19. Glottal Size

20. Vocal Fold Stiffness

21. “Effective” Mass and Length

22. Learning Objectives • Outline and briefly describe the different types of sounds that can be produced by the larynx.

23. Laryngeal Sound Generation • Transient vs. Continuous • Glottal stops • Aperiodic vs. Periodic • Glottal fricatives • Whispering • Voice production/phonation

24. Laryngeal Sound Generation Glottal stop Glottal fricative

25. Learning Objectives • Describe a single cycle of vocal fold oscillation • Describe why phonation is considered “quasi-periodic” • Describe the relationship between vocal fold motion (kinematics), laryngeal aerodynamics and sound pressure wave formation • Describe and draw idealized waveforms and spectra of the glottal sound source

26. Complexity of vocal fold vibration Vertical phase difference Longitudinal phase difference

27. The Glottal Cycle

28. Phonation is actually quasi-periodic • Complex Periodic • vocal fold oscillation • Aperiodic • Broad frequency noise embedded in signal • Non-periodic vocal fold oscillation • Asymmetry of vocal fold oscillation • Air turbulence

29. Flow Glottogram

30. Synchronous plots Sound pressure waveform (microphone at mouth) Glottal Airflow (inverse filtered mask signal) Glottal Area (photoglottogram) Vocal Fold Contact (electroglottogram)

31. Sound pressure wave Instantaneous sound pressure Time

32. Learning Objectives • Explain vocal fold motion using the 2-mass model version of the myoelastic-aerodynamic theory of phonation

33. Glottal Aerodynamics: Some Terminology • Subglottal pressure • Translaryngeal Pressure (Driving Pressure) • Translaryngeal Airflow (Volume Velocity) • Laryngeal Airway Resistance • Phonation Threshold Pressure • Initiate phonation • Sustain phonation

34. Myoelastic Aerodynamic Theory of Phonation Necessary and Sufficient Conditions • Vocal Folds are adducted (Adduction) • Vocal Folds are tensed (Longitudinal Tension) • Presence of Aerodynamic pressures (driving pressure)

35. 2-mass model Upper part of vocal fold Mechanical coupling stiffness Lower part of vocal fold Coupling between mucosa & muscle TA muscle

36. Definitions of terms • Pme:myoelastic pressure (aka laryngeal opposing pressure) • Psg: subglottal pressure • Patm: atmospheric pressure • Pwg: pressure within the glottis • Utg: transglottal (translaryngeal) airflow

37. VF adducted & tensed→myoelastic pressure (Pme) • Glottis is closed • subglottal air pressure (Psg) ↑ • Psg ~ 8-10 cm H20, Psg>Pme • L and R M1 separate • Transglottal airflow (Utg) = 0 • As M1 separates, M2 follows due to • mechanical coupling stiffness • Psg > Pme • glottis begins to open • Psg > Patmtherefore Utg > 0

38. Utg↑ ↑ since glottal aperature << tracheal circumference Utg↑ Pwg↓ due to Bernoulli effect Pressure drop within the glottis Bernoulli’s Law P + ½ U2 = K where P = air pressure  = air density U = air velocity

39. Utg↑ Pwg↓ due to Bernoulli effect* Pwg< Pme M1 returns to midline M2 follows M1 due to mechanical coupling stiffness Utg = 0 Pattern repeats 100-200 times a second

40. Role of glottal shape • Current theories argue that Bernoulli effect plays a relatively small role in vocal fold closure. • More important is glottal shape. Pwg is lower for ‘divergent’ vs. ‘convergent’ shape. • As the glottis become divergent, Pwgdrops resulting in the Pwg< Pme

42. Limitations of this simple model

43. Learning Objectives • Describe how speakers control fundamental frequency. • Provide expected values for different measures of fundamental frequency. • Describe different methods for measuring fundamental frequency. • Describe how speakers control sound pressure level. • Provide expected values for different measures of sound pressure level.

44. Quantifying frequency • Hertz: cycles per second (Hz) Non-linear scales • Octave scale • 1/3 octave bands • Semitones • Cents • Other “auditory scales”: e.g. mel scale

45. Fundamental Frequency (F0)Control What factors dictate the vibratory frequency of the vocal folds? • Anatomical factors Males ↑ VF mass and length = ↓ Fo Females ↓ VF mass and length = ↑ Fo • Subglottal pressure adjustment – show example ↑ Psg = ↑ Fo • Laryngeal and vocal fold adjustments ↑ CT activity = ↑ Fo TA activity = ↑ Fo or ↓ Fo • Extralaryngeal adjustments ↑ height of larynx = ↑ Fo

46. Average F0 speaking fundamental frequency (SFF) Correlate of pitch Infants ~350-500 Hz Boys & girls (3-10) ~ 270-300 Hz Young adult females ~ 220 Hz Young adult males ~ 120 Hz Older females: F0↓ Older males: F0↑ F0 variability F0 varies due to Syllabic & emphatic stress Syntactic and semantic factors Phonetics factors (in some languages) Provides a melody (prosody) Measures F0 Standard deviation ~2-4 semitones for normal speakers F0 Range maximum F0 – minimum F0 within a speaking task Characterizing Fundamental Frequency (F0)

47. F0 in the first 10 years of life

48. F0 over the lifespan

49. Estimating the limits of vocal fold vibration Maximum Phonational Frequency Range • highest possible F0 - lowest possible F0 • Not a speech measure • measured in Hz, semitones or octaves • Males ~ 80-700 Hz1 • Females ~135-1000 Hz1 • Around a 3 octave range is often considered “normal” 1Baken (1987)

50. Approaches to Measuring Fundamental Frequency (F0) • Time domain vs. frequency domain • Manual vs. automated measurement • Specific Approaches • Peak picking • Zero crossing • Autocorrelation • The cepstrum & cepstral analysis