ECE 598: The Speech Chain. Lecture 9: Consonants

Transcription

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 SyllableInitial 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 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. bat. Very Brief History: 1446: King Sejong of Chosen publishes a distinctivefeature based phonetic notation for Korean. 1867: Alexander Melville Bell publishes a distinctivefeature featurebased 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 SAMPA i / y I / Y e / / u U? / o E / 9 { a 3 V / O A / Q * SAMPA: An international standard for the ASCII transcription of the IPA phonemes. Maps most IPA phones to the ASCII printable characters.

6 Vowels: Sample Words From With phonological feature annotation. All are [syllabic]. Lax Vowels [reduced,lax[ reduced,lax,blade]: lax: like IPA central, central, but also short duration I pit pit [high,front high,front] ] high: like IPA close. close. E pet pet [high,front] V cut kvt [high, high,front] U put put [high,front] Tense Vowels: [reduced,[ reduced,lax] i ease iz [low,high,front]] low: like IPA open. open. Specified if [high,[ high,lax] e raise rez [low, low,high,front] { pat p{t [low,front low,front] u lose luz [low,high, low,high,front,round] ] [round]: o nose noz [low, low,high, high,front,round] ] possible if [lax,[ lax,front] O cause koz [low,front,round front,round] A pot fad@ [low,front, front,round] round] Classic Diphthongs: ai rise raiz OI noise noiz au rouse rauz Schwa and Syllabic /r/: 3 furs f3 z z [reduced,lax,blade[ reduced,lax,blade,anterior, corner korn@ [reduced,blade reduced,blade,anterior, anterior,distributed]

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

8 Obstruent Consonants: Sample Words From With phonological feature annotation. All are [syllabic].[ Stops [sonorant,[ sonorant,continuant]: p pin pin [lips,round, round,voice] b bin bin [lips,round,voice round,voice] t tin tin [blade,anterior blade,anterior,distributed, distributed,voice] anterior: of the alveolar ridge d din din [blade,anterior, blade,anterior,distributed,voice] ] distributed: tongue tip flat k kin kin [body,high body,high,voice] g give giv [body,high,voice body,high,voice] Affricates [sonorant,[ sonorant,continuant]: ts chin tsin dz gin dzin [blade,anterior,distributed anterior,distributed,voice] [blade,anterior,distributed,voice anterior,distributed,voice] Fricatives [sonorant,continuant[ sonorant,continuant]: f fin fin [lips,round, round,voice] v vim vim [lips,round,voice round,voice] T thin TIn [blade,anterior,distributed blade,anterior,distributed,voice] D this DIs [blade,anterior,distributed,voice blade,anterior,distributed,voice] s sin sin [blade,anterior blade,anterior,distributed, distributed,voice] z zin zin [blade,anterior, blade,anterior,distributed,voice] S shin SIn [blade,anterior,distributed anterior,distributed,voice] Z measure mez@ [blade,anterior,distributed,voice anterior,distributed,voice] h hit hit [glottal] voicing is not specified, depends on context

9 DoublyArticulated Consonants SAMPA w H

10 Sonorant Consonants: Sample Words Mostly from With phonological feature annotation Flap [sonorant,continuant, continuant,nasal, nasal,syllabic]: syllabic]: 4 butter bv43 [blade,anterior blade,anterior,distributed] distributed] Nasals [sonorant,continuant,nasal continuant,nasal]: m mock mak [lips,round, round,syllabic] n knock nak [blade,anterior blade,anterior,distributed, distributed,syllabic] syllabic] =n button bv4=n [blade,anterior, blade,anterior,distributed,syllabic] N thing TIN [body,high body,high,syllabic] Liquids [sonorant,continuant sonorant,continuant,syllabic]: syllabic]: r wrong ron [blade,anterior, anterior,distributed] l long lon [blade,anterior blade,anterior,distributed] distributed] Glides [sonorant,continuant sonorant,continuant,syllabic]: syllabic]: w wasp wasp [lips,round lips,round] j yacht jat [blade,anterior, anterior,distributed]

11 Examples: SAMPA 1. You wish to know all about my grandfather. Well, he is nearly ninety three years old, but he still thinks as swiftly as ever. 2. ju wis tu no Al mai wel,, hi iz nirli naintitri yirz old, bvt hi stil Tinks }z swiftli }z

12 Example: Phonological Feature Matrix Example: Phonological Feature Matrix [high] [high] [pharyngeal/low] [pharyngeal/low] [lax] [lax] [lips] [lips] [glottal] [glottal] [voice] [voice] [nasal] [nasal] [front] [front] [body] [body] [distributed] [distributed] [anterior] [anterior] [blade] [blade] [round] [round] [reduced] [reduced] [continuant] [continuant] [sonorant] [sonorant] [syllabic] [syllabic] K I t s u

13 NonPulmonic Consonants

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

15 Nasal Murmur the mug the nut sing a song Observations: Lowfrequency resonance (about 300Hz) always present Lowfrequency resonance has wide bandwidth (about 150Hz) Energy of lowfrequency resonance is very constant Most highfrequency resonances cancelled by zeros Different places of articulation have different high frequency spectra Highfrequency spectrum is talkerdependent and variable

16 Acoustic Description of Vocal Tract with a Side Branch U N (0,ω) A P U P (0,ω) U M (0,ω) A M L P 0 Continuity Equations at the Juncture (x=0): 1. Conservation of mass 2. Continuity of pressure u P (0,ω)u N (0,ω)u M (0,ω)=0 p P (0,ω)=p N (0,ω)=p M (0,ω) L M x

17 Reminder: How to Calculate Impedance of a Uniform Tube 1. Express u(x,ω), p(x,ω) ) in terms of p and p p(x,ω) ) = p e jωx/c p e jωx/c u(x,ω) ) = A v(x,ω) ) = (A/( A/ρc)(p e jωx/c p e jωx/c 2. Impose one boundary condition 1. u(l,ω)=0: p = p e 2j or 3. p(l,ω)=0: p = p e 2j 2jωL/c 2jωL/c 3. Calculate impedance at the other boundary 1. z(0,ω) ) = p(0,ω)/v(0, )/v(0,ω)) = (ρc)(p( p )/(p p ) or 3. z(0,ω) ) = p(0,ω)/u(0, )/u(0,ω)) = (ρc/a)(p( p )/(p p ) 4. Result (for a uniform tube, using z=p/u p/u): 1. u(l,ω)=0: z(0,ω) ) = j(ρc/a)cot( c/a)cot(ωl/c) 2. or 3. p(l,ω)=0: z(0,ω) ) = j( j(ρc/a)tan( c/a)tan(ωl/c) x/c )

18 Resonant Frequencies ( Formants( Formants ) of a Nasal Consonant 1. Air Flow from Pharynx must equal Air Flow to Nose and Mouth u P u N u M =0 2. Therefore, the admittances sum to zero (1/z P )(1/z N )(1/z M )=0 3. Plug in the true admittances j(a P /ρc)tan( c)tan(ωl P /c)j(a N /ρc)cot( c)cot(ωl N /c)j(a M /ρc)tan( c)tan(ωl M /c)=0 4. For most resonant frequencies: Eq.. (3) must be solved numerically on a computer (or graphically, as in Fujimura, JASA 1962)

19 First Nasal Formant 1. The true resonance equation: ja P tan(ωl P /c)ja N cot(ωl N /c)ja M tan(ωl M /c)=0 2. Lowfrequency approximation: A P (ωl P /c)a N /(ωl N /c)a M (ωl M /c)=0 (A M L M A P L P )(ω/c) 2 A N /L N =0 ω 2 = c 2 (A N /L N )/(A M L M A P L P ) 3. Typical example, nasal F 1 : A P L P =60cm 3, A M L M =40cm 3, A N /L N =(3.5cm 2 /9cm) = 2/5cm F 1 =(c/2π)(1/250) 1/2 350Hz

20 Nasal Consonant Formants = Resonances of the OralNasal NasalPharyngeal 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 AntiResonances 1. AntiResonances (zeros) occur because of energy lost into the sidebranch 2. Continuity of pressure at the juncture: p P (0,ω)=p N (0,ω)=p M (0,ω) 3. If it turns out that p N (0,ω)=0, that s s OK; that s just part of the normal standing wave pattern in the nostrils. 4. If it turns out that p M (0,ω)=0, that s 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 AntiResonances 1. AntiResonances (zeros) occur at any frequency such that, regardless of um(0,w), p M (0,ω) ) is required to be zero 2. In other words: z M (0,ω)= )=p M /u M =0 3. Uniform tube: z M (0,ω)=( )=(ρc/a M )cot(ωl M /c) 4. Therefore F zm 5. Anti zm =(mc/2l M )(c/4l M ) Antiresonances of the English nasal consonants: 1. /m/: L M 8cm, F zm 1100, 3300, 5500Hz 2. /n/: L M 5cm, F zm 1700, 5100, 8500Hz 3. /ng/: L M 2cm, F zm 4400Hz,

23 /l/: Liquids Main airway: around the tongue (on both sides, so there may be zeros because of added transfer functions) Side branch: above the tongue /r/: L = 6cm F Z = 35400/4L = 1500Hz, between F2 and F3, pushes F2 down Main airway: as in a vowel Side branch: under the tongue L = 3.5cm F Z = 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 Unaspirated (/b/) Transient Frication Aspiration Voicing Aspirated (/t/)

27 Prevoicing 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 lowfrequency 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: F R = c/4l f Example: FR=2250 = c/4l f L f = 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

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 (oralnasal nasalpharyngeal) Zeros=resonances of side branch (P=0 at juncture) Events in the Release of a SyllableInitial Stop Consonant Transient pop, pop, triangular shape, about 0.5ms long Frication = turbulence at the constriction, about 5ms Aspiration = turbulence at glottis, 070ms0 Formant Transitions may start during aspiration (in the case of an unvoiced stop release)