Greg Detre
Tuesday, 10 October, 2000
Dr Utman, LT-C
Lecture � L&C II Speech Production
Acoustics of
speech production
vocal folds/cords (glottis) + vocal tract
glottis located in larynx (voice box) � 2 flaps of skin attached to bits of cartilege, which are moved by muscles to flap the flaps together
adduction (move them together) / abduction (move them apart)
gross movements, make fine pitch distinctions
vowels: close the vocal folds, blow outwards, produces sub-glottal pressure on the flaps, blows them open and closed again (very rapidly, 100-300/s) producing a buzzing, raspberry sound = phonation (building block of speech, basis of many vowel and some consonant sound). it�s a passive property of air passing through the vocal folds, rather than being actively generated by the muscles
the rate they open + close varies the pitch
the pitch + quality of the voice depends on the tension of the vocal cords (and how carefully you can control them), as well as the physical quality of the vocal folds themselves
thickness + length of vocal cords affect your fundamental frequency (pitch)
children have higher fundamental frequency than adults, because vocal cords lengthen with age. men�s are longer than women�s (hence, deeper)
Tubes/cavities
oral (mouth)
pharyngeal (throat)
nasal
Points of articulation
teeth/alveolar ridge (right behind your teeth) (�tttt�)
hard palate (�shhh�) / velum (�kkkk�, �gggg�) (a little floppy thing at the back)
Articulators
tongue
lips
velum
larynx (vocal folds)
Consonants are usually produced by (partially) closing the vocal tracts at different points along the tube
Articulation = the timing + execution of the articulators
languages vary from 3-46 vowels, 6-95 consonants
Linguists classify the consonant sounds according to 3 dimensions:
place = the location of the constriction of the closure along the vocal tract
voicing = presence or absence of phonation in the vocal folds
manner = implementation of these articulatory movements
Voicing �ba� and �pa�
both labial (articulated by the lips), but they differ in the lag time between the opening of the lips and the opening/closing of the vocal cords = voice onset time (VOT)
ba VOT = 0-20ms (some people even pre-voice)���������������������������������������������������������������������������������������� (= a voiced consonant)
pa VOT = 40-120ms���������������������������������������������������������������������������������������� (= a voiceless consonant)
stopped consonant = somewhere along the vocal tract, you�re stopping the airflow (�ba�, �pa�)
fricatives = partial closure along the vocal tract, gives a kind of turbulent noise (e.g. �ssss�, �ffff�)
affricate = combination of fricative and stopped
semi-vowels (�ra�, �la� �)
nasal
liquid
glide
Different language have different combinations of place, voicing and manner
classify vowels according to:
height
backness (�oooo� = back, �eeee� = front)
rounding (with your lips, �oooo� = rounded�, �eeee� is not)
vowel features
vowel space (the dimensions of height, backness and roundedness)
the quantal vowels are �i�, �u� and �a� = the easiest vowels to distinguish from an articulatory standpoint and to listen to
they occur in all the world�s languages
languages vary in their phonemic inventory
phoneme = the smallest distinguishable sound in a language
minimal pairs = words that vary by only one phoneme
each phoneme can be made up of a selection of features in phoneme space (e.g. both �pa� and �ba� are bilabial, stopped, but �pa� is aspirated and not voiced, and vice versa for �ba�)
aspiration = a breathy �hhhh� sound, but is not considered a phonemic contrast
allophones = variations for the same phoneme, e.g. aspirated �pit� vs non-aspirated �spit�, �top� vs �stop�
aspiration is predictable according to a phonological rule, in English (for any stopped unvoiced consonant)
phonotactics = the rules governing which sounds can be combined to form legitimate words in a language
debates about the fundamental unit of speech sounds (syllable vs phoneme etc.) � though many speech sounds require a consonant-vowel combination to produce
most of the information we need to tell the sounds comes from transitions (the dynamic nature of speech)
average male glottis phonates at a fundamental frequency of 100Hz
produces a systematic increase + decrease of pressure, creating a wave of sound (pockets of dense + not so dense air), which we perceive as the human voice
harmonics = naturally occurring at multiples of frequencies (harmonic stack) (if you cut off someone�s head, you�d just hear a basic buzzing)
damping = obstructing the sound source
the vocal tract is a tube, and filters out some of the sounds
tubes resonate (e.g. blowing into a bottle, makes a humming noise), i.e. certain frequencies (i.e. multiples) passing through are reinforced
the resonance depends on the length of the tube
average vocal tract length = 16-17cm
characterise resonances of half-closed tube = 500Hz, 1500Hz and 2500Hz
the thickness of vocal tract affects fundamental frequency because it changes the speed of opening/closing
the glottis (vocal folds) = the source
your tongue can change the filter functions (characteristics) of your vocal tract by opening/closing it
is the sub-glottal pressure �voicing�?
what�s the larynx? is it the vocal folds/box???
vocal folds = plural?