Stop + Approximant Acoustics

November 28, 2012

Updates

• Formant measuring exercise has been graded… • Fricative + stop transcription exercise is still due on Friday.

• Production Exercise #4 due on Monday after the weekend… • By the way: Production Exam!

Voiced Aspirated

• Some languages distinguish between (breathy) voiced aspirated and voiceless aspirated stops and affricates.

• Check out Hindi:

[p h al]

Hindi voiced + breathy aspirated [d h ol] Bengali 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”

[bag]

The Velar Pinch

[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

[f] = ?

• Labio-dental and interdental fricatives are the most confusable consonants in English.

• In some dialects of English, may be replaced by [f].

• • “with” “mouth” • Stephen Fry transcription • May be distinguished visually: check out the clips.

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 [i] [u] [y] Glide [j] [w] Place palatal labio-velar (front, unrounded) (back, rounded) 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:]