Transcript 23-FricativesVOT

Fricatives + Voice Onset Time
March 31, 2014
In the Year 2000
• Today: we’ll wrap up fricatives…
• and then move on to stops.
• This Friday, there will be one final transcription exercise.
• On Bengali, Quebecois French, and Arabic.
• I just posted it right before class.
Acoustic Enhancement
• Note:
is post-alveolar and [s] is alveolar
•  more space in vocal tract in front of
• including a “sub-lingual cavity”
• This “filter” of
resonates at lower frequencies
• In English, this acoustic distinction is enhanced
through lip rounding for
• this extends the vocal tract
• further lowers the resonant frequencies of
The Sub-lingual Cavity
•Let’s check the videotape...
Behind the Constriction
[s]
• Let’s check the ultrasound…
Other Examples
• Susie and David say “speech”:
• Also: Where the shtreets have no name
• And: Tina Fey
• Note: there are no word-initial /sr/ sequences in English.
•
“shriek”
*“sreek”
Polish
• Note: lip-rounding can be used to enhance other fricative
contrasts
• In Polish, it enhances the contrast between (post-)alveolar
and dental fricatives
• the (post-)alveolars have the rounding
Polish, continued
• Polish also has what are known as alveolo-palatal
fricatives.
• = constriction in the post-alveolar region
• + raised tongue in the palatal region (behind the fricative)
Polish Sibilants
vs.
Palatography
[kasa]
Palatography
Polish Clusters
• Just for kicks...
Four Fricatives
Mandarin Sibilants
• Mandarin Chinese also has dental, post-alveolar and
alveolo-palatal sibilant fricatives.
• The post-alveolars are sometimes retroflex
Mandarin
Before I forget…
• There are two remaining fricative symbols in the IPA
that we have yet to learn.
1. Some dialects of English still have a voiceless
labio-velar fricative (a voiceless /w/):
2. In Swedish, there is a fricative which combines the
articulations of post-alveolar
and velar [x]:
Affricates
• Affricates are transcribed
as stop-fricative sequences
•
• Acoustically, amplitude
rises faster in affricates
than in plain fricatives
• “rise time”
• Phonologically, affricates
are [-continuant]
Affricate Typology
• More numbers from the UPSID database:
• 522 affricates in 316 languages
•
141
• [ts] 95
•
80
• [dz] 30
• 485 affricates have sibilant fricatives
• Other affricate types are rarer:
• [pf] (German) [tx] (Navajo)
Fricative vs. Affricate
“shy”
“chime”
Polish, Again
• Polish contrasts affricates with stop + fricative sequences
Stop + Fricative vs. Affricate
Fricative Acoustics Summary
• Turbulence provides the source of fricative noise
• Voiced fricatives also have a sound source at the glottis
• Obstacle turbulence tends to be louder than channel
turbulence
• Sibilants are particulary high in intensity
• The filter of fricative turbulence noise changes depending on
the place of articulation
• sibilants: very short filter, emphasizing high frequencies
• labials: essentially no filter (flat spectrum)
• back fricatives: longer, more vowel-like filter
• Affricates: stop-fricative sequences with shorter rise time
Review: Stops and Voicing
• Stops
• Three stages: close, maintain, release
• Pressure build-up behind closure
• “Release Burst”
• Voicing
• Vocal folds are lightly brought together (adducted)
• Sub-glottal pressure higher than supra-glottal
pressure
• Airflow through glottis causes cycle of vocal fold
opening and closing
• Voiceless: k > t > p
Voiced: b > d > g
It’s not that simple
•
The voicing of stops is difficult, so the contrast between
voiced and voiceless stops often takes a different form
•
•
Making use of a different property: aspiration
An aspirated stop has the following timing:
1. Stop closure is made
2. Airflow builds up pressure behind closure
3. Closure is released (with a “burst”)
4. Air flows unimpeded through glottis (“aspiration”)
5. Vocal folds close; voicing begins
An Aspirated Stop: [phœt]
aspiration
release burst
voicing (vowel)
[t] closure
[t] release burst
An Unaspirated Stop: [pœt]
release burst voicing (vowel)
A Voiced Stop: [byt]
release burst
voicing (closure) voicing (vowel)
Voice Onset Time
• Voice Onset Time (VOT) is defined as the length of time
between the release of a stop closure and the onset of
voicing.
• For aspirated stops--voicing begins after the release, so:
• VOT  50 - 150 milliseconds
• For unaspirated stops--voicing begins at the release, so:
• VOT  0 - 20 milliseconds
• For voiced stops--voicing begins before the release, so:
• VOT < 0 milliseconds
(VOT can be negative)
Thai Stops
• In stressed onset position, English distinguishes
between:
• unaspirated and aspirated stops.
• Languages like French, Dutch and Spanish distinguish
between:
• voiced and voiceless unaspirated stops.
• Thai splits up the VOT continuum into three parts:
• voiced, voiceless unaspirated, voiceless aspirated
Thai Stops
[ba]
[pa]
English Stop Contrasts
1. In onset position:
•
/p/ is voiceless aspirated
•
/b/ is voiceless unaspirated
2. In medial position (between voiced segments):
•
/p/ is voiceless unaspirated
•
/b/ is voiced
3. After /s/, in the same syllable:
•
only voiceless unaspirated stops (no contrast)
Beak, Peak, Speak
Rabid vs. Rapid
English Stop Contrasts
4. In syllable-final position:
•
•
vowels preceding /p/ are short
•
vowels preceding /b/ are longer
•
/p/ closure tends to be longer than /b/ closure
Moral of the story:
•
Phonological voiced vs. voiceless contrast in
English is abstract
•
It may exhibit different phonetic manifestations
•
Phonemes vs. Allophones