Articulation L5 - Speech Production Moodle.pptx

Speech Production Air flow • A steady-state, unmodulated, subglottal air supply can be placed under pressure by introducing resistance to airflow • Resistance to air flow can occur at a number of points along the vocal tract • Resistance to air flow at the level of the larynx leads to a glottal tone...

Speech Production Air flow • A steady-state, unmodulated, subglottal air supply can be placed under pressure by introducing resistance to airflow • Resistance to air flow can occur at a number of points along the vocal tract • Resistance to air flow at the level of the larynx leads to a glottal tone • Vibratory movements of the vocal folds initiate sounds to be modified by articulatory changes in the vocal tract to produce speech sounds Speech Production Vocal Folds • When the vocal folds vibrate, they release one short-duration burst of air into the vocal tract each cycle • If vocal folds vibrate at a rate of 150 times per second, the fundamental frequency is 150 Hz. • Voice is a complex tone. It has a fundamental frequency, but also harmonics. Speech Production Vocal Tract • Vocal tracts have a natural resonant frequency of vibration. • Each chamber in the vocal tract has a different resonant frequency (depending on the size and shape of the chamber). • The larger the cavity, the lower the frequency (males vs females) • Vibrations die away quickly because their vibratory energy is dissipated: damping Spectrogram A graphic representation of three dimensions of sounds in terms of their component frequencies is called a spectrogram. • Time is always represented on the x-axis • Frequency (pitch) on the yaxis • Intensity (loudness) is depicted by the relative darkness of the frequencies shown Formants • Formants are the frequencies that are being best resonated based on the configuration of the vocal tract. • Differences in how the vocal tract resonates the column of air, produce different formants. • The spectrogram represents the intensity – loudness- of the frequencies in the speech sound including formants. Speech Production • A vocal tone comes from the larynx. • That tone gets modified by the size and shape of the vocal tract. Movements of articulators such as teeth, tongue, cheeks change the cavity, therefore change the frequencies of the tone e.g., /α/, /o/, /u/ • The modifications produce formants (e.g., F1, F2, F3) of different frequencies Speech Production Parameters of Vocal Tract Vibrations and Modifications • Vibrations generated by the vocal folds have 3 parameters: frequency, intensity, duration; • In order to produce speech, these vibrations must be modified by the structures that lie between the vocal folds and the mouth • Most modifications can be accounted for by the principles of resonance and damping (the opposite of resonance) Resonance As tension of the vocal folds increases, rate of vocal fold vibration increases. As mass of the vocal folds increases, rate of vocal fold vibration decreases. These two aspects dictate fundamental frequency As the size of a vocal tract increases, the frequencies that resonate decrease As the size of the vocal tract decreases, the frequencies that resonate increase (children, small tubes high frequencies) These two aspects dictate formants frequencies Characteristics of the Glottal Sound Source Laryngeal tone is complex; composed of many different frequencies Fundamental frequency is determined by the rate at which the vocal folds are vibrating (tension and mass). Partials are harmonics (whole number multiples) of the fundamental frequency. The harmonics that are enhanced are determined by the size and shape of the cavities in the resonator (vocal tract). Depending on the vocal tract configuration certain frequencies will resonate, while other frequencies will dampen. • If the Fundamental Frequency = 100 Hz (100 vibrations per second) then the laryngeal tone = 100 Hz + whole number multiples of 100 Hz (e.g., 200, 300, 400 Hz) • Amplitude of partials ↓ as frequency ↑. The loudness of the harmonics decreases as the frequency increases. Males typically have more harmonics in their voices • Fundamental Frequency + Partials → the source spectrum generated by the larynx; this is the raw material which is shaped by the vocal tract to produce speech. Haskins Lab Yale.edu Source Filter Model • The configuration of the vocal tract approximates that of a uniform tube: the crosssectional area is fairly uniform • Average vocal tract length: – adult males = 17.5 cm – adult females = 14.7 cm – very small children = 8.75 cm • Think of the vocal tract as a uniform tube, closed at one end (because of the high resistance at the glottis compared to virtually no resistance at the lips) • Resonance curves of the vocal tract represent its transfer function, i.e., filter shape Source Filter Model • Tube closed at one end resonates best at a frequency which has a wavelength 4 times the length of the tube. It will resonate at frequencies that are oddnumbered multiples of the lowest resonant frequency. • For a tube 17.5 cm in length the first resonant frequency would be 485.7 Hz; if we round this to 500 Hz, the second resonance would be at 1500 Hz (500 x 3) and the 3rd at 2500 Hz (500 x 5). • The first two or three formants are necessary for correct vowel perception. F1 F2 F3 Formant Frequencies (Resonances) F1 F2 F3 Source: VF Filter: Output: vocal tract VF spectrum shaped by the vocal tract Effects of Configurations of the Vocal Tract Formant frequencies are determined by the length and shape of the vocal tract: • As vocal tract is lengthened, all the formant frequencies ↓ • As vocal tract is shortened, the frequencies ↑ (that’s why we find highest formants in children, lowest in adult males) • Changes in the cross-sectional area of the vocal tract will also shift individual formant frequencies: for vowels – Tongue Height (high, mid, low) – largely responsible for F1 – Tongue Placement (front, central, back) – largely responsible for F2 /i/ /ɪ/ /ɛ/ /æ/ Let’s look at the effect of tongue height on F1 /i/ / ɪ/ / ɛ/ /æ/ Let’s look at the effect of tongue front to back position on F2 Vowels Four aspects of an articulatory gesture shape the vocal tract for vowel production 1. point of major constriction – tongue placement (front, central, back) 2. degree of constriction – tongue height (high, mid, low) 3. degree of lip rounding (spread, rounded) 4. degree of muscle tension (tense, lax) Vowels: lip rounding and muscle tension Lip rounding Spread: lips are in a comparatively spread position [i] [I] Rounded: lips are in a comparatively round position [o] [u] Muscle tension Serves to differentiate vowels which share almost precisely the same place and degree of constriction, and lip rounding Tense: more heightened muscular activity; longer in duration; more powerful acoustically. You can hold it out [i] Lax: less heightened muscular activity. You can’t hold it out [I] Diphthong Vowels •A blend of two consecutive vowels, spoken within the same syllable •Tongue changes position during production •There are three major diphthongs in American English: – /aɪ/ (bite) – /aʊ/ (cow) – /ɔɪ/ (boy) Diphthong Vowels (in Isolation) /aɪ/ /aʊ/ /ɔɪ/ Vowel Articulation • The vocal tract does not affect the frequency of the harmonics in the glottal source; it reinforces the amplitudes of those harmonics that coincide or nearly coincide with the natural frequencies (resonances or formants) of the vocal tract. • Each vowel in English is characterized by its own unique energy distribution or spectrum due to resonances (formants); the spectrum is the consequence of the cross-sectional area properties and length of the vocal tract; these changes in the acoustic properties are mediated by the articulators. F1 F2 F3 Vowel Articulations - Formants Length of the Vocal Tract • First formant frequency will have a wavelength that is four times the length of the tube • Frequencies of the formants are inversely proportional to the length of the vocal tract • Anything that increases the effective length of the vocal tract (lip rounding, depression of the larynx) will lower all formants – Vowels with lip rounding, have lower formants. Consonants • Characterized physiologically by an obstruction of the vocal tract • Consonants comprise about 62% of sound in running speech; vowel comprise about 38% • Consonants often initiate and terminate syllables • Consonants carry more information than vowels do; contrast in meaning between two words is more often conveyed by a minimal difference between consonants than it is between vowels • Accents are usually present in the vowels; that’s why you can understand most accents. • Consonants are shorter in duration than vowels Classification of Consonants • Place of Articulation: describes where the consonant is made or point of constriction; includes – – – – – use of lips (labial, bilabial) gums (alveolar) hard palate (palatal) soft palate (velar) glottis (glottal) • Manner of Articulation: describes the degree of constriction as a consonant is produced, in other words describes how the sound is made: – – – – – Stops/plosives Fricatives Affricates Nasals Glides/liquids, semivowels Classification of Consonants • Voicing: each consonant can be classified as either voiced or unvoiced Voiced sounds: produced with the vocal folds vibrating; primary excitation source is the larynx with a secondary constriction somewhere along the vocal tract • Often a given articulatory gesture is associated with a pair of consonants that differ only in their voiced-unvoiced feature • Cognates: pairs of consonants with same articulation, but differ in whether they are voiced or voiceless • Examples include [b] and [p], [z] and [s], and [v] and [f] Classification on the Basis of Articulation: Place, Manner, Voicing j #1 The vowel /i/ is a high-front vowel. First and second formant frequencies (F1 and F2) will be A. Middle and low B. High and low C. Low and middle D. High and middle E. Low and high #1 The vowel /i/ is a high-front vowel. First and second formant frequencies (F1 and F2) will be A. Middle and low B. High and low C. Low and middle D. High and middle E. Low and high #2 Vocal fold vibration initiates sound that includes A. Formant frequencies B. Fundamental frequency C. Harmonics D. A. and B. E. B and C. #2 Vocal fold vibration initiates sound that includes A. Formant frequencies B. Fundamental frequency C. Harmonics D. A. and B. E. B and C. F1 F2 F3 #3 Consonants are characterized by the following articulatory features A. First and Second Formants B. Tongue Tip, Blade, Front, Back C. Place, Manner, Voicing D. Tongue Height and Front/Back Position #3 Consonants are characterized by the following articulatory features A. First and Second Formants B. Tongue Tip, Blade, Front, Back C. Place, Manner, Voicing D. Tongue Height and Front/Back Position Stops • Dependent upon complete closure of the vocal tract at some point • Articulation usually occurs at lips (b/p), with tongue against the alveolar ridge (d/t) and with the tongue against the soft palate (g/k) • Production of stop consonants is very dependent upon integrity of the speech mechanism; the articulators must be brought into full contact, firmly, to resist the air pressure being generated Fricatives • Generated by a noisy excitation of the vocal tract turbulence of air) is generated at some constriction along the vocal tract • Except for /h/ which is generated at the glottis, all voiced fricatives have a voiceless cognate • In English fricatives can be produced with the following places of articulation: labiodental (v/f), dental (/δ/ the; /ɵ/ theta), alveolar (z/s), palatal (/ʒ/ azure; /ʃ/ shoe), glottal (h) Glides and Liquids (semivowels) • Characterized by frequency transitions during production, voicing, radiating from the mouth, and a lack of nasal coupling • They are very vowel-like, except that they are generated with more vocal tract constriction than are the vowels • Place of articulation forms glides: palatal (/j/ you) and labial (/w/ we) and liquids: palatal (/r/ red) and alveolar (/l/ as in let) Nasals • Nasals are voiced: excitation from vibrating vocal folds • Nasal sounds in American English are produced with complete constriction of the vocal tract by lips /m/, tongue at the alveolar ridge /n/, or dorsum of tongue against hard and/or soft palate /ŋ/ • The nasopharyngeal port is opened so most of the sound radiated is from the nostrils Coarticulation • Coarticulation occurs when two or more speech sounds overlap in such a way that their articulatory gestures blend from one sound to the next. • Try to sound out “can” /kæn/ by producing each phoneme separately. Then say the whole word. Because of coarticulation the vowel /æ/ takes on a nasal quality in transition to producing the final consonant /n/. • Coarticulation is a necessary component of speech physiology due to the very rapid nature of speech sound production. Role of Feedback in Speech Production Auditory Feedback • Auditory feedback: a principal avenue by which we monitor our speech production Motor Feedback • There is also interaction between the motor and other sensory modalities which control our speech production mechanism Swallowing • • • • Swallowing or deglutition is a basic biological function Initiating a swallow is voluntary Completing a swallow is reflexive Swallowing is a demanding activity involving the lips, tongue, velopharynx, jaw, lower pharynx, larynx, hyoid bone, and the esophagus; • Neurological coordination required for swallowing places demands on a number of cranial nerves • Injury or disease almost anywhere in the head and neck can lead to dysphagia a difficulty in swallowing. Swallowing • Swallowing has 4 stages that are not discrete movements, yet rather they follow in rapid succession: – Oral Prep stage is voluntary and includes putting food/liquid in the oral cavity, mastication, and bolus formation. – Oral stage is movement of the bolus from the anterior oral cavity to the posterior oral cavity. The swallow is initiated (reflexive part) once the bolus reaches the anterior faucial pillars. – Pharyngeal stage is a variety of movements for airway protection. The epiglottis flips down, the laryngeal complex moves anteriorly and superiorly, the vocal folds close, respiration stops, the upper esophageal sphincter (cricopharyngeus muscle) opens, and the bolus moves from the oropharynx into the esophagus. – Esophageal stage – the bolus moves from the upper esophagus to the lower esophagus and into the stomach. Evaluation of Swallowing Normal Swallow Animation Normal Modified Barium Swallow Study Abnormal Modified Barium Swallow Study Announcements • Exam review session is – Tuesday Nov 28, 6:30-8:00 pm, Zoom • Exam is Thursday Nov 30 – Bonus questions will address innervation of the main muscles