speech science fall 2009 oct 28, 2009. outline acoustical characteristics of nasal speech sounds...
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The Articulation and Acoustics of Consonants
Speech ScienceFall 2009
Oct 28, 2009
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OutlineAcoustical characteristics of
Nasal Speech SoundsStop ConsonantsFricativesAffricates
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Acoustics of the NasalsThe addition of nasal cavity creates vocal
tract a longer and larger resonator.Therefore, it naturally responds to lower
frequencies.Acoustic result is called “murmur”This murmur or formant lies within the 200-
300 Hz range Acoustically, nasal consonants are weak due
to antiresonances within the vocal tract.
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Acoustics of the NasalsThe antiresonances are frequency regions in which
the amplitudes of the source components are severely attenuated.
Consonants are articulated with more constriction or occlusions than vowels.
Resonances and antiresonances can cancel each other if those frequencies are close enough or one formant may appear as two.
The elongated vocal tract also causes weak nasal consonants.
Antiresonances can also attributed to soft walls of nasal cavity
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Acoustics of the NasalsThe frequency ranges
for the antiresonances associated with nasal sounds vary with place of articulation.
For /m/, antiresonance is in the range of 500-1500 Hz.
For /n/, the range is between 2000-3000 Hz and for / /, it is above 3000 Hz.
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Nonresonant Consonants: StopsStop consonantsVoiceless: /p/, /t//
and /k/Voiced: /b/, /d/,
and /g/These sounds are
articulated with the greatest degree of obstruction to the breath stream
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Stops: Acoustic features1) Silent gapIt is the hold period
in articulation (no flow of air out of the vocal tract)
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Stops: Acoustic features2) Noise burst It is at the moment of
releaseIt appears as a vertical
line in spectrogramsNoise bursts are very
brief (i.e., 10-35 ms) and covers broad range of frequencies with varying intensity
Most intense frequency depends upon the place of articulation
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Stops: Acoustic features3) Rise and fall timeThe speed with which
the acoustic signal attains maximum intensity (syllable initial stops) or falls to minimum intensity (for syllable final stops)
Rise and fall times are both very rapid for stop consonants
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Stops: Acoustic features4) Change in F1The first formant rises
rapidly after the release of initial stops
It falls rapidly before the completion of the closure for the final stops.
(review: first formant frequency is positively correlated with the size of mouth opening).
This rise and fall depend upon the neighboring vowels.
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Stops: Acoustic featuresStops: Place of articulationA) Most intense frequency
of the transient burst varies with place of articulation.
/p/ and /b/ generally have maximum intensity around 600 Hz and below.
/t/ and /d/ have most intensity in high frequency area around 3000 Hz.
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Stops: Acoustic featuresStops: Place of
articulation/k/ and /g/ present a
variable picture.Spectral peaks of
bursts are associated F2 of the following vowel after stop.
Intense portion of burst extends upward from the f2 of the following vowel.
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Stops: Acoustic featuresStops: Place of articulationB) Formant transitionRight after occlusion is
released, the rapid movements of the articulators cause sudden change in resonance peaks of vowel tract.
They occur during transition from one speech sound to another
They are called formant transitions.
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Stops: Acoustic featuresStops: Place of
articulationB) F2 transition(review: F2 was
correlated with the length of the front cavity)
For stops, F2 varies with the neighboring vowel.
Direction of frequency change in F2 changes with vowel preceding or following a stop.
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Formant transitions
http://www.umanitoba.ca/faculties/arts/linguistics/russell/phonetics/acoustic/img/formant-transitions.png
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Stops: Acoustic featuresStops:Voiced and voicelessDuring intervocalic
contexts, for /b/, /d/, and /g/, phonation continues through out the period of articulatory closure.
For /p/, /t/, /k/, phonation ceases during closure.
During prevocalic contexts, we do not normally phonate during the closure of above sounds.
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Stops: Acoustic featuresStops:Voice onset time (VOT)For /b/, /d/, and /g/,
phonation begins at or very shortly after stop release.
For /p/, /t/, and /k/, there is a delay of at least 50 ms before phonation begins after the release.
This relative timing of stop release and the initiation of phonation has been called voice onset time (VOT).
Lisker and Abramson
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Stops: Acoustic featuresVOT : it is measured in
milliseconds as the duration between the onset of transient burst of stop release and the first vocal pulse.
If onset of phonation follows stop release, VOT values are positive.
If voicing onset precedes stop release, VOT values are negative.
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Stops: Acoustic featuresStops:AspirationIt is a period of voicelessness
after stop release.It is associated only with
/p/, /t/, and /k/.Open glottis at the moment
of stop release allows the breath stream to flow freely into the upper vocal tract without generating phonation.
The reverse is true for voiced stops.
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FricativesEnglish fricatives have
five articulatory positions: labio-dental: f,v - fine, vine
dental: þ,ð - think, this
alveolar: s,z - price, prize
post-alveolar: , - mission, vision
glottal: h - hard
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FricativesThe fricative noise
originates at the articulatory constriction.
Spectrum at the lips is determined by the resonant characteristics of the constriction and portion of the vocal tract anterior to the noise source.
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Fricatives For /v/, and /f/, fricative energy is
very low in intensity because there is no appreciable resonating cavity anterior to the point of constriction. But frequency band is broad.
/s/ and /z/ have a very narrow band of frequency and high energy noise.
For /s/, most of the energy is above 4000 Hz.
For [ʃ], it energy is around 2000 Hz because point of articulation is farther back in the mouth, thus resonating cavity anterior to that is longer .
This results in lower frequencies for [ʃ] than /s/.
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AffricatesAcoustically, these
sounds present combination of stop and fricative featuresStop closureBust noise (release
of stop)Extended duration
of aperiodic sound (friction)