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ECE 598: The Speech Chain

ECE 598: The Speech Chain. Lecture 9: Consonants. Today. International Phonetic Alphabet History SAMPA – an IPA for ASCII Sounds with a Side Branch Nasal Consonants Reminder: Impedance of a uniform tube Liquids: /l/, /r/ Events in the Release of a Syllable-Initial Stop Consonant

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ECE 598: The Speech Chain

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  1. ECE 598: The Speech Chain Lecture 9: Consonants

  2. Today • International Phonetic Alphabet • History • SAMPA – an IPA for ASCII • Sounds with a Side Branch • Nasal Consonants • Reminder: Impedance of a uniform tube • Liquids: /l/, /r/ • Events in the Release of a Syllable-Initial Stop Consonant • Transient and Frication Sources • Aspiration • Formant Transitions

  3. Topic #1:International Phonetic Alphabet

  4. International Phonetic Alphabet: Purpose and Brief History • Purpose of the alphabet: to provide a universal notation for the sounds of the world’s languages • “Universal” = If any language on Earth distinguishes two phonemes, IPA must also distinguish them • “Distinguish” = Meaning of a word changes when the phoneme changes, e.g. “cat” vs. “bat.” • Very Brief History: • 1446: King Sejong of Chosen publishes a distinctive-feature based phonetic notation for Korean. • 1867: Alexander Melville Bell publishes a distinctive-feature-based universal phonetic notation in “Visible Speech: The Science of the Universal Alphabetic.” His notation is rejected as being too expensive to print. • 1886: International Phonetic Association founded in Paris by phoneticians from across Europe; begins developing IPA notation. • 1991: Unicode provides a standard method for including IPA notation in computer documents.

  5. International Phonetic Alphabet: Vowels SAMPA i / y I / Y e / 2 E / 9 { a SAMPA ? / u U ? / o V / O A / Q @ 3 * SAMPA: An international standard for the ASCII transcription of the IPA phonemes. Maps most IPA phones to the ASCII printable characters.

  6. Vowels: Sample WordsFrom http://www.phon.ucl.ac.uk/home/sampa/american.htmWith phonological feature annotation. All are [+syllabic]. • Lax Vowels [-reduced,+lax,-blade]: lax: like IPA “central,” but also short duration • I pit pIt [+high,+front] high: like IPA “close.” • E pet pEt [-high,+front] • V cut kVt [-high,-front] • U put pUt [+high,-front] • Tense Vowels: [-reduced,-lax] • i ease iz [-low,+high,+front] low: like IPA “open.” Specified if [-high,-lax] • e raise rez [-low,-high,+front] • { pat p{t [+low,+front] • u lose luz [-low,+high,-front,+round] [+round]: • o nose noz [-low,-high,-front,+round] possible if [-lax,-front] • O cause kOz [+low,-front,+round] • A pot fAD@’ [+low,-front,-round] • Classic Diphthongs: • aI rise raIz • OI noise nOIz • aU rouse raUz • Schwa and Syllabic /r/: • 3’ furs f3’z [-reduced,+lax,+blade,-anterior,-distributed] • @ allow @laU [+reduced,-blade] • @’ corner kOrn@’ [+reduced,+blade,-anterior,-distributed]

  7. IPA: Regular Consonants Tongue Body Tongue Blade ? gq k p b t d n m N 4 h B f v T D s z S Z C x G r j l L

  8. Obstruent Consonants: Sample WordsFrom http://www.phon.ucl.ac.uk/home/sampa/american.htmWith phonological feature annotation. All are [-syllabic]. • Stops [-sonorant,-continuant]: • p pin pIn [+lips,-round,-voice] • b bin bIn [+lips,-round,+voice] • t tin tIn [+blade,+anterior,-distributed,-voice] anterior: of the alveolar ridge • d din dIn [+blade,+anterior,-distributed,+voice] distributed: tongue tip flat • k kin kIn [+body,+high,-voice] • g give gIv [+body,+high,+voice] • Affricates [-sonorant,-continuant]: • tS chin tSIn [+blade,-anterior,+distributed,-voice] • dZ gin dZIn [+blade,-anterior,+distributed,+voice] • Fricatives [-sonorant,+continuant]: • f fin fIn [+lips,-round,-voice] • v vim vIm [+lips,-round,+voice] • T thin TIn [+blade,+anterior,+distributed,-voice] • D this DIs [+blade,+anterior,+distributed,+voice] • s sin sIn [+blade,+anterior,-distributed,-voice] • z zin zIn [+blade,+anterior,-distributed,+voice] • S shin SIn [+blade,-anterior,+distributed,-voice] • Z measure mEZ@’ [+blade,-anterior,+distributed,+voice] • h hit hIt [+glottal] --- voicing is not specified, depends on context

  9. Doubly-Articulated Consonants SAMPA w H

  10. Sonorant Consonants: Sample WordsMostly from http://www.phon.ucl.ac.uk/home/sampa/american.htmWith phonological feature annotation • Flap [+sonorant,-continuant,-nasal,-syllabic]: • 4 butter bV43’ [+blade,+anterior,-distributed] • Nasals [+sonorant,-continuant,+nasal]: • m mock mAk [+lips,-round,-syllabic] • n knock nAk [+blade,+anterior,-distributed,-syllabic] • =n button bV4=n [+blade,+anterior,-distributed,+syllabic] • N thing TIN [+body,+high,-syllabic] • Liquids [+sonorant,+continuant,-syllabic]: • r wrong rON [+blade,-anterior,-distributed] • l long lON [+blade,+anterior,-distributed] • Glides [+sonorant,+continuant,-syllabic]: • w wasp wAsp [+lips,+round] • j yacht jAt [+blade,-anterior,-distributed]

  11. Examples: SAMPA • You wish to know all about my grandfather. Well, he is nearly ninety-three years old, but he still thinks as swiftly as ever. • ju wIS tu no Al @baUt maI gr}ndfaD@r. wEl, hi iz nirli naInti-Tri yirz old, bVt hi stIl Tinks }z swIftli }z Ev@r.

  12. Example: Phonological Feature Matrix

  13. Non-Pulmonic Consonants

  14. Topic #2:Sounds with Side Branches: Nasal Consonants, /l/, /r/

  15. Nasal Murmur “the mug” “the nut” “sing a song” Observations: Low-frequency resonance (about 300Hz) always present Low-frequency resonance has wide bandwidth (about 150Hz) Energy of low-frequency resonance is very constant Most high-frequency resonances cancelled by zeros Different places of articulation have different high frequency spectra High-frequency spectrum is talker-dependent and variable

  16. Acoustic Description of Vocal Tract with a Side Branch UN(0,w) Continuity Equations at the Juncture (x=0): • Conservation of mass uP(0,w)+uN(0,w)+uM(0,w)=0 • Continuity of pressure pP(0,w)=pN(0,w)=pM(0,w) AP AM UP(0,w) UM(0,w) x 0 -LP LM

  17. Reminder: How to Calculate Impedance of a Uniform Tube • Express u(x,w), p(x,w) in terms of p+ and p- p(x,w) = p+e-jwx/c + p-ejwx/c u(x,w) = A v(x,w) = (A/rc)(p+e-jwx/c - p-ejwx/c) • Impose one boundary condition • u(L,w)=0: p- =p+e2jwL/c • ... or … • p(L,w)=0: p- = -p+e2jwL/c • Calculate impedance at the other boundary • z(0,w) = p(0,w)/v(0,w) = (rc)(p++p-)/(p+-p-) • ... or … • z(0,w) = p(0,w)/u(0,w) = (rc/A)(p++p-)/(p+-p-) • Result (for a uniform tube, using z=p/u): • u(L,w)=0: z(0,w) = j(rc/A)cot(wL/c) • … or … • p(L,w)=0: z(0,w) = -j(rc/A)tan(wL/c)

  18. Resonant Frequencies (“Formants”) of a Nasal Consonant • Air Flow from Pharynx must equal Air Flow to Nose and Mouth uP+uN+uM=0 • Therefore, the admittances sum to zero (1/zP)+(1/zN)+(1/zM)=0 • Plug in the true admittances -j(AP/rc)tan(wLP/c)+j(AN/rc)cot(wLN/c)-j(AM/rc)tan(wLM/c)=0 • For most resonant frequencies: Eq. (3) must be solved numerically on a computer (or graphically, as in Fujimura, JASA 1962)

  19. First Nasal Formant • The true resonance equation: -jAPtan(wLP/c)+jANcot(wLN/c)-jAMtan(wLM/c)=0 • Low-frequency approximation: -AP(wLP/c)+AN/(wLN/c)-AM(wLM/c)=0 -(AMLM+APLP)(w/c)2+AN/LN=0 w2 = c2(AN/LN)/(AMLM+APLP) • Typical example, nasal F1: APLP=60cm3, AMLM=40cm3, AN/LN=(3.5cm2/9cm) = 2/5cm F1=(c/2p)(1/250)1/2 ≈ 350Hz

  20. Nasal Consonant Formants = Resonances of the Oral-Nasal-Pharyngeal Combined System Fourth Nasal Resonance ≈ 2400 Third Nasal Resonance ≈ 1800 Second Nasal Resonance ≈ 1400 First Nasal Resonance ≈ 350Hz, with broad bandwidth B ≈ 300Hz

  21. Nasal Consonant Anti-Resonances • Anti-Resonances (zeros) occur because of energy lost into the side-branch • Continuity of pressure at the juncture: pP(0,w)=pN(0,w)=pM(0,w) • If it turns out that pN(0,w)=0, that’s OK; that’s just part of the normal standing wave pattern in the nostrils. • If it turns out that pM(0,w)=0, that’s extra: it means that the side branch (into the mouth) is draining away all of the energy that would otherwise go out through the nostrils.

  22. Nasal Consonant Anti-Resonances • Anti-Resonances (zeros) occur at any frequency such that, regardless of uM(0,w), pM(0,w) is required to be zero • In other words: zM(0,w)=pM/uM=0 • Uniform tube: zM(0,w)=(rc/AM)cot(wLM/c) • Therefore Fzm=(mc/2LM)-(c/4LM) • Anti-resonances of the English nasal consonants: • /m/: LM ≈ 8cm, Fzm ≈ 1100, 3300, 5500Hz • /n/: LM ≈ 5cm, Fzm ≈ 1700, 5100, 8500Hz • /ng/: LM ≈ 2cm, Fzm ≈ 4400Hz, …

  23. Liquids • /l/: • Main airway: around the tongue (on both sides, so there may be zeros because of added transfer functions) • Side branch: above the tongue • L = 6cm • FZ = 35400/4L = 1500Hz, between F2 and F3, pushes F2 down • /r/: • Main airway: as in a vowel • Side branch: under the tongue • L = 3.5cm • FZ = 2500Hz, between F3 and F4, pushes F3 down

  24. Topic #3:Events in the Release of a Stop (Plosive) Consonant

  25. Events in the Release of a Stop “Burst” = transient + frication (the part of the spectrogram whose transfer function has poles only at the front cavity resonance frequencies, not at the back cavity resonances).

  26. Events in the Release of a Stop Transient Frication Aspiration Voicing Aspirated (/t/) Unaspirated (/b/)

  27. Pre-voicing during Closure To make a voiced stop in most European languages: Tongue root is relaxed, allowing it to expand so that vocal folds can continue to vibrating for a little while after oral closure. Result is a low-frequency “voice bar” that may continue well into closure. In English, closure voicing is typical of read speech, but not casual speech. “the bug”

  28. Transient: The Release of Pressure

  29. Transfer Function During Transient and Frication: Poles Turbulence striking an obstacle makes noise Front cavity resonance frequency: FR = c/4Lf Example: FR=2250 = c/4Lf Lf = 4cm “the shutter”

  30. Transfer Function During Frication: An Important Zero

  31. Transfer Function During Frication: An Important Zero

  32. Transfer Function During Aspiration

  33. Formant Transitions: A Perceptual Study The study: (1) Synthesize speech with different formant patterns, (2) record subject responses. Delattre, Liberman and Cooper, J. Acoust. Soc. Am. 1955.

  34. Perception of Formant Transitions

  35. Summary • International Phonetic Alphabet • “Distinct” = distinguishes words • “Universal” = distinct any language → distinct in IPA • Sounds with a Side Branch • Poles=poles of entire system (oral-nasal-pharyngeal) • Zeros=resonances of side branch (P=0 at juncture) • Events in the Release of a Syllable-Initial Stop Consonant • Transient “pop,” triangular shape, about 0.5ms long • Frication = turbulence at the constriction, about 5ms • Aspiration = turbulence at glottis, 0-70ms • Formant Transitions may start during aspiration (in the case of an unvoiced stop release)

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