Transcript Administrative Stuff

Stop + Approximant Acoustics
November 30, 2011
Updates
• Grading of Production Exercise #3 continues apace.
• Production Exercise #4 has been posted.
• due on Wednesday the 7th
Voiced Aspirated
• Some languages distinguish between (breathy) voiced
aspirated and voiceless aspirated stops and affricates.
• Check out Hindi:
[phal]
Hindi
[dhol]
Bengali
voiced +
breathy
aspirated
voiced +
aspirated
Zhu|hoasi Stop Contrasts
• Zhu|hoasi is spoken in northern Namibia.
• Last but not least, Korean makes an interesting distinction
between “emphatic” (or fortis) obstruents and unaspirated
(lenis) and aspirated obstruents.
What’s going on here?
•
A variety of things are going on in the articulation of
fortis consonants in Korean.
1. Glottis does not open as wide as in lenis stops.
 Voicing begins more quickly after stop release
2. Vocal folds are more tense than in lenis stops.
3. Increased airflow in fortis stops.
 Higher F0 after stop release.
A Basic Distinction
• Vowels
• Relatively unconstricted flow of air through vocal tract
(above the glottis)
• Shape (filter) the source of sound made at the glottis
• Consonants
• Completely or severely constricted flow of air through
vocal tract (above the glottis)
• Create a source of sound at the constriction (e.g.,
release bursts, turbulence)
• Voicing may be difficult
• Note: this is a phonological distinction, not a phonetic one.
Obstruents and Sonorants
• Phonologically speaking, there are also different kinds of
consonants.
• One important distinction is between obstruents and
sonorants.
• Obstruents
• Stops, fricatives, affricates
• Obstruct flow of air through the vocal tract so much that
voicing is difficult
• Sonorants
• Nasals, approximants (glides, liquids), trills, flaps
• Allow air to flow freely through vocal tract so that
resonance (voicing) is still possible
Stop Acoustics Overview
•
Stages of Stop Production
1. Closing
2. Closure
3. Release
4. Opening
•
Acoustic Cues for Place of Articulation
1. Formant transition out of vowel
2. Closure voicing {or nothing}
3. Release burst
4. Formant transition into vowel
Release Bursts
• The acoustic characteristics of a stop release burst tend
to resemble those of a fricative made at the same place
of articulation.
• Ex: labial release bursts have a very diffuse spectrum,
just like bilabial and labio-dental fricatives.
[p] burst
Release Bursts: [t]
• Alveolar release bursts tend to lack acoustic energy at
the bottom of the spectrum.
• To some extent, higher frequency components are
more intense.
[t] burst
Release Bursts: [k]
• Velar release bursts are relatively intense.
• They also often have a strong concentration of energy
in the 1500-2000 Hz range (F2/F3).
• There can often be multiple [k] release bursts.
[k] burst
Closure Voicing
• During the stop closure phase, only low frequency
information escapes from the vocal tract (for voiced stops)
• “voicing bar” in spectrogram
• analogy: loud music from the next apartment
Armenian:
[bag]
• This acoustic information provides hardly any cues
to place of articulation.
[bag] vs. [bak]
• From Armenian (another language from the Caucasus)
[bag]
[bak]
Formant Transitions
• The resonant frequencies of the vocal tract change as
stop gestures enter or exit the closure phase.
• Ex: Formant frequencies usually decrease in making the
transition from bilabial stop to vowel (or vice versa)
Formant Transitions: alveolars
• For other places of articulation, the type of formant
transition that appears is more complex.
• From front vowels into alveolars, F2 tends to slope
downward.
• From back vowels into alveolars, F2 tends to slope
upwards.
[hid]
[hæd]
Formant Locus
• Whether in a front vowel or back vowel context...
• The formant transitions for alveolars tend to point to
the same frequency value. ( 1650-1700 Hz)
• This (apparent) frequency value is known as the locus of
the formant transition.
• According to one theory of perception...
• the locus frequency can be used by listeners to
reliably identify place of articulation.
Velar Transitions
• Velar formant transitions do not always have a reliable
locus frequency for F2.
• Velars exhibit a lot of coarticulation with neighboring
vowels.
• Fronter (more palatal) next to front vowels
• Locus is high: 1950-2000 Hz
• Backer (more velar) next to back vowels
• Locus is lower: < 1500 Hz
• F2 and F3 often come together in velar transitions
• “Velar Pinch”
The Velar Pinch
[bag]
[bak]
Fricative Transitions
• You get transition cues for fricatives at different places of
articulation, too.
Transitions
• American
:
tongue tip
between teeth
• British
:
tongue tip behind
upper teeth
•
has a little bit
of a transition cue
Approximants
•
Approximants = one articulator is close to another, but
without producing audible turbulence.
•
They come in two flavors:
1. Glides (English [w], [j])
2. Liquids (English
, [l])
• This distinction is also phonological…
• Glides are essentially high-vowel articulations which
are not in a syllabic peak.
• In English, liquids may form syllables (or syllable
peaks).
Glides
• Each glide corresponds to a different high vowel.
Vowel
Glide
Place
[i]
[j]
palatal
(front, unrounded)
[u]
[w]
labio-velar
(back, rounded)
[y]
labial-palatal (front, rounded)
velar
(back, unrounded)
Glide Examples
• French contrasts palatal, labio-palatal and labio-velar
glides:
• Japanese has velar vowels, but not necessarily velar
glides...
Glide Acoustics
• Glides are shorter than vowels
• They also tend to lack “steady states”
• and exhibit rapid transitions into (or from) vowels
• hence: “glides”
• Also: lower in intensity
• especially in the higher formants
[j] vs. [i]
[w] vs. [u]
Vowel-Glide-Vowel
[iji]
[uwu]
More Glides
[wi:]
[ju:]