The Articulation and Acoustics of Consonants

Speech ScienceFall 2009

Oct 28, 2009

OutlineAcoustical characteristics of

Nasal Speech SoundsStop ConsonantsFricativesAffricates

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.

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

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.

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

Stops: Acoustic features1) Silent gapIt is the hold period

in articulation (no flow of air out of the vocal tract)

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

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

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.

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.

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.

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.

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.

Formant transitions

http://www.umanitoba.ca/faculties/arts/linguistics/russell/phonetics/acoustic/img/formant-transitions.png

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.

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

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.

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.

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

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.

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/.

AffricatesAcoustically, these

sounds present combination of stop and fricative featuresStop closureBust noise (release

of stop)Extended duration

of aperiodic sound (friction)