Behrman Chapter 5 6 Place less emphasis on

Behrman Chapter 5, 6 Place less emphasis on… • Minor anatomical landmarks and features • Extrinsic muscles of the larynx • Blood supply to the larynx • Central motor control of larynx • Peripheral Sensory control of larynx • Stress-Strain Properties of Vocal Folds

Laryngeal Activity in Speech/Song • Sound source to excite the vocal tract – Voice – Whisper • Prosody – Fundamental frequency (F 0) variation – Amplitude variation • Realization of phonetic goals – – – Voicing Devoicing Glottal frication (/ /, / /) Glottal stop (/ /) Aspiration • Para-linguistic and extra-linguistic roles – Transmit affect – Speaker identity

The vocal fold through life… • 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 Glottal Cycle

http: //video. google. com/videosearch? source=ig&hl=en&rlz=&q=high%20 speed%20 video%20 voice&um=1&ie=UTF-8&sa=N&tab=wv Complexity of vocal fold vibration Vertical phase difference Longitudinal phase difference

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

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

• VF adducted & tensed → myoelastic pressure (Pme ) • Glottis is closed • subglottal air pressure (Psg) ↑ • Psg ~ 8 -10 cm H 20, Psg > Pme • L and R M 1 separate • Transglottal airflow (Utg) = 0 As M 1 separates, M 2 follows due to mechanical coupling stiffness Psg > Pme glottis begins to open Psg > Patm therefore Utg > 0

Utg ↑ ↑ since glottal aperature << tracheal circumference Utg ↑ Ptg ↓ due to Bernoulli effect Pressure drop across the glottis Bernoulli’s Law P + ½ U 2 = K where P = air pressure = air density U = air velocity

Utg ↑ Ptg ↓ due to Bernoulli effect Plus “other” aerodynamic effects Ptg < Pme M 1 returns to midline M 2 follows M 1 due to mechanical coupling stiffness Utg = 0 Pattern repeats 100 -200 times a second

Limitations of this simple model

The Glottal Cycle

Instantaneous sound pressure Sound pressure wave Time

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 • Voicing vs. whispering

Glottal Aerodynamics • Volume Velocity • Driving Pressure • Phonation Threshold Pressure – Initiate phonation – Sustain phonation • Laryngeal Airway Resistance

Measuring Glottal Behavior • Videolaryngoscopy – Stroboscopy – High speed video

illumination Photoglottography (PGG) Time

Electroglottography (EGG) • Human tissue = conductor • Air: conductor • Electrodes placed on each side of thyroid lamina • high frequency, low current signal is passed between them • VF contact = impedance

Electroglottogram

Glottal Airflow (volume velocity) • Instantaneous airflow is measured as it leaves the mouth • Looks similar to a pressure waveform • Can be inverse filtered to remove effects of vocal tract • Resultant is an estimate of the airflow at the glottis

Flow Glottogram

Synchronous plots Sound pressure waveform (at mouth) Flow glottogram (inverse filtered mask signal) Photoglottogram Electroglottogram

F 0 Control • 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

Fundamental Frequency (F 0) Average F 0 • • 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: F 0 ↓ Older males: F 0 ↑ F 0 variability • F 0 varies due to – Syllabic & emphatic stress – Syntactic and semantic factors – Phonetics factors (in some languages) • Provides a melody (prosody) • Measures – F 0 Standard deviation • ~2 -4 semitones for normal speakers – F 0 Range

Maximum Phonational Frequency Range • • • highest possible F 0 - lowest possible F 0 Not a speech measured in Hz, semitones or octaves Males ~ 80 -700 Hz 1 Females ~135 -1000 Hz 1 3 octaves often considered normal 1 Baken (1987)

Fundamental Frequency (F 0) Control • Ways to measure F 0 – Time domain vs. frequency domain – Manual vs. automated measurement – Specific Approaches • • Peak picking Zero crossing Autocorrelation The cepstrum & cepstral analysis

Autocorrelation Data Correlation + 1. 0 + 0. 1 - 0. 82 + 0. 92

Cepstrum

Amplitude Control • Subglottal pressure adjustment ↑ Psg = ↑ sound pressure • Laryngeal and vocal fold adjustments ↑ medial compression = ↑ sound pressure • Supralaryngeal adjustments

Measuring Amplitude • Pressure • Intensity • Decibel Scale

Sound Pressure Level (SPL) Average SPL • Correlate of loudness • conversation: • ~ 65 -80 d. BSPL Variability • SPL to mark stress • Contributes to prosody • Measure – Standard deviation for neutral reading material: • ~ 10 d. BSPL

Dynamic Range • Amplitude analogue to maximum phonational frequency range • ~50 – 115 d. B SPL

Vocal Quality • no clear acoustic correlates like pitch and loudness • However, terms have invaded our vocabulary that suggest distinct categories of voice quality Common Terms • Breathy • Tense/strained • Rough • Hoarse

Are there features in the acoustic signal that correlate with these quality descriptors?

Breathiness Perceptual Description • Audible air escape in the voice Physiologic Factors • Diminished or absent closed phase • Increased airflow Potential Acoustic Consequences • Change in harmonic (periodic) energy – Sharper harmonic roll off • Change in aperiodic energy – Increased level of aperiodic energy (i. e. noise), particularly in the high frequencies

harmonics (signal)-to-noise-ratio (SNR/HNR) • harmonic/noise amplitude • HNR – Relatively more signal – Indicative of a normality • HNR – Relatively more noise – Indicative of disorder • Normative values depend on method of calculation • “normal” HNR ~ 15

Harmonic peak Amplitude Noise ‘floor’ Harmonic peak Noise ‘floor’ Frequency

First harmonic amplitude From Hillenbrand et al. (1996)

Prominent Cepstral Peak

Spectral Tilt: Voice Source

Spectral Tilt: Radiated Sound

Peak/average amplitude ratio

From Hillenbrand et al. (1996)

WMU Graduate Students

Tense/Pressed/Effortful/Strained Voice Perceptual Description • Sense of effort in production Physiologic Factors • Longer closed phase • Reduced airflow Potential Acoustic consequences • Change in harmonic (periodic) energy – Flatter harmonic roll off

Spectral Tilt Pressed Breathy

Perception of Effort Acoustic Basis of Vocal Effort F 0 + RMS + Open Quotient Tasko, Parker & Hillenbrand (2008)

Roughness • Perceptual Description – Perceived cycle-to-cycle variability in voice • Physiologic Factors – Vocal folds vibrate, but in an irregular way • Potential Acoustic Consequences – Cycle-to-cycle variations F 0 and amplitude – Elevated jitter – Elevated shimmer

Period/frequency & amplitude variability • Jitter: variability in the period of each successive cycle of vibration • Shimmer: variability in the amplitude of each successive cycle of vibration …

Jitter and Shimmer Sources of jitter and shimmer • Small structural asymmetries of vocal folds • “material” on the vocal folds (e. g. mucus) • Biomechanical events, such as raising/lowering the larynx in the neck • Small variations in tracheal pressures • “Bodily” events – system noise Measuring jitter and shimmer • Variability in measurement approaches • Variability in how measures are reported • Jitter – Typically reported as % or msec – Normal ~ 0. 2 - 1% • Shimmer – Can be % or d. B – Norms not well established

Vocal Register What is a vocal register?

Vocal Registers Pulse (Glottal fry) – – – 30 -80 Hz, mean ~ 60 Hz Closed phase very long (90 % cycle) May see biphasic pattern of vibration (open, close a bit, open and close completely) Low subglottal pressure (2 cm water) Energy dies out over the course of a cycle so parts of the cycle has very little energy Hear each individual cycle

Vocal Registers Modal – – – VF are relatively short and thick Reduced VF stiffness Large amplitude of vibration Possesses a clear closed phase The result is a voice that is relatively loud and low in pitch Average values cited refer to modal register

Vocal Registers Falsetto – – – – 500 -1100 Hz (275 -600 Hz males) VF are relatively long and thin Increased VF stiffness Small amplitude of vibration Vibration less complex Incomplete closure (no closed phase) The result is a voice that is high in pitch