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 (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

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

Complexity of vocal fold vibration Vertical phase difference Longitudinal phase difference 8&sa=N&tab=wv#

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 Lower part of vocal fold Upper part of vocal fold Mechanical coupling stiffness TA muscle Coupling between mucosa & muscle

VF adducted & tensed → myoelastic pressure (P me ) Glottis is closed subglottal air pressure (P sg ) ↑ P sg ~ 8-10 cm H 2 0, P sg > P me L and R M1 separate Transglottal airflow (U tg ) = 0 As M1 separates, M2 follows due to mechanical coupling stiffness P sg > P me glottis begins to open P sg > P atm therefore U tg > 0

U tg ↑ ↑ since glottal aperature << tracheal circumference U tg ↑ P tg ↓ 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

U tg ↑ P tg ↓ due to Bernoulli effect Plus “other” aerodynamic effects P tg < P me M1 returns to midline M2 follows M1 due to mechanical coupling stiffness U tg = 0 Pattern repeats times a second

Limitations of this simple model

The Glottal Cycle

Sound pressure wave Time Instantaneous sound pressure

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

Photoglottography (PGG) Time illumination

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 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 = ↓ F o Females ↓ VF mass and length = ↑ F o Subglottal pressure adjustment – show example ↑ P sg = ↑ F o Laryngeal and vocal fold adjustments ↑ CT activity = ↑ F o TA activity = ↑ F o or ↓ F o Extralaryngeal adjustments ↑ height of larynx = ↑ F o

Fundamental Frequency (F 0 ) Average F 0 speaking fundamental frequency (SFF) Correlate of pitch Infants –~ Hz Boys & girls (3-10) –~ Hz Young adult females –~ 220 Hz Young adult males –~ 120 Hz Older females: F0 ↓ Older males: F0 ↑ 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 measure measured in Hz, semitones or octaves Males~ Hz 1 Females~ 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

Cepstrum

Amplitude Control Subglottal pressure adjustment ↑ P sg = ↑ 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: ~ dB SPL SPL Variability  SPL to mark stress Contributes to prosody Measure –Standard deviation for neutral reading material: ~ 10 dB SPL

Dynamic Range Amplitude analogue to maximum phonational frequency range ~50 – 115 dB 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 Noise ‘floor’ Frequency Amplitude Harmonic peak

From Hillenbrand et al. (1996) First harmonic amplitude

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

Pressed Breathy Spectral Tilt

Acoustic Basis of Vocal Effort F0 + RMS + Open Quotient Perception of Effort 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 F0 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 ~ % Shimmer –Can be % or dB –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 – Hz ( 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