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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.
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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:
voiced + breathy aspirated Hindi [dhol] voiced + aspirated Bengali
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. • Glottis does not open as wide as in lenis stops. • Voicing begins more quickly after stop release • Vocal folds are more tense than in lenis stops. • 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 • Closing • Closure • Release • Opening • Acoustic Cues for Place of Articulation • Formant transition out of vowel • Closure voicing {or nothing} • Release burst • 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: • Glides (English [w], [j]) • 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
Vowel-Glide-Vowel [iji] [uwu]
More Glides [wi:] [ju:]