anatomic aspects larynx: sytem of muscles, cartileges and ligaments. primarly for controlling vocal...
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Anatomic Aspects
• Larynx: Sytem of muscles, cartileges and ligaments.
• Primarly for controlling vocal folds• Folds 13-15mm
• Glottis: Slit like opening between folds• Folds move and change tension• Vocal folds and epiglottis close during
eating (also false vocal folds)• False vocal folds are likely open during
speech prouction
Larynx
Top View
Voicing Breathing
Three Primary States of Vocal Folds: Breathing, Voiced and Unvoiced
• BREATHING: Arytenoid cartileges move outward, fold muscles are relaxed.
• VOICING:The size/mass and tension of folds determines pitch (60-400 Hz)
MOTION OF FOLDS DURING VOICING
Mechanical Model of Folds
Periodic Glottal Flow Velocity
Mathematical Model of Glottal Flow
Glottal flow waveform
npngnu *
Glottal flow over a single cycle (imp. Resp.)
Impulse train
;
k
kPnnp
P : pitch period
Looking through a small window ,nw
npngnwnu *,,
Absence of window would yield impulses
k
k
GWP
U
*,1
,
Practical Phenomena
• Fixed pitch is not possible even in sustained cases “pitch jitter”
• Airflow velocity within a glottal cycle may differ across consecutive periods “shimmer”
• Jitter and shimmer yield “naturalness” and contributes to the “voice character”.
UNVOICING no vibration of vocal folds
Folds are close to each other but open and tense
Turbulance / aspiration/h/ whisper
• Aspiration normally occurs during voicing also.• If strong breathy voice.
Other Forms of Vocal Fold Movement
• Creaky Voice: Folds are very tense and vibrating part is small. – It is a harsh sounding voice.– High and irregular pitch is observed.
• Vocal Fry: When folds are massy and relaxed.– Abnormally low and irregular pitch.– Secondary glottal pulses arise within the open phase– Folds may couple with false vocal folds.– Vocal fry may ocur in normal speech at the edn of a phrase when
folds relax and lung pressure decreases.
• Diplophonic: Secondary pulses in the closed phase.– Generally in low pitch speakers.– It may arise in normal voices at the end of a phrase or word.
• Vocal fry and diplophonic can be modelled as
0~ nngngng
Vocal Fry
Diplophonic
Vocal Tract
~17 cm and up to ~20 cm2
• Vocal tract colors the source• It also generates new sources for sound production• It can be approximated by a linear filter.
– Resonance frequencies are called “formants”
– Formant bandwidth and formant amplitude.
• The peaks of the spectrum of vocal tract response are approximately formants.
00r
formant
00
jer
Related to bandwidth
All-pole model
• ck : pole, resonance freq., formant
• Formants: F1, F2, ... From low-to-high
• In general, formant frequencies decreaseas vocal tract length increases. (male, female, child)
iN
kkk zczc
AzH
1
1*1 11
Vocal Tract Output
Vocal tract impulse response
npngnhnx **
In a small window (to pick a stationary portion)
nxnwnx ,,
kkGHW
PX *,
1,
k
kkk WGHP
X ,1
,
Speech Sounds - Phonemes
• Broad classification is “vowels” and “consonants”.• Finer classification:
Vowels
Front
Center
Back
Consonants
Nasals
Plosives
Whispers
Fricatives
Voiced
Unvoiced
Voiced
Unvoiced
Transitional
Affricates
chew
just
Diphtongs
hide
boy
out
new
Semi-Vowels
Liquids
read
let
Glides
we
you
• Vowels: No constriction along the vocal tract.– Voiced. Vocal folds vibrate. – Front, center or back; according to the tongue position.– Rounded, unrounded according to the position of lips.– Also, high-low according to tongue height.
• Normal breathing yields low sound. The high intensity of vowels is because of vocal fold vibration.
Vowels
Fricatives
Plosives
Nasals
Transitional Sounds
Spectrogram of the diphtong /O/ in “boy”.