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Syllables and Stress
October 24, 2011
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Practicalities Review session on Wednesday.
Mid-term on Friday.
Note: well deal with the outstanding transcription
homeworks on Wednesday
(reference transcriptions will be posted to the course
web page)
On Wednesday, well also take a listen to the accents ofEnglish samples (Scottish + Boston)
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Review: Suprasegmentals
Last time, we learned that there were three kinds of
languages:
1. Tone languages (Chinese, Navajo, Igbo)
lexically determined tone on every syllable or word
2. Accentual languages (Japanese, Swedish)
the location of an accent is lexically marked.
3. Stress languages (English, Russian)
its complicated
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What is Stress? Examples of stress in English:
(V) vs. (N)
(V) vs. (N)
Phonetically, stress is hard to define
I.e., it is hard to measure.
It seems to depend on an interaction of three
quantifiable variables:
Pitch
Duration
Loudness
And also: quality
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Loudness
How do we measure how loud a sound is?
Recall: one parameter of a sinewave is its amplitude.
Peak amplitude (for sound) is the highest sound pressure
reached during a particular wave cycle.
peak-to-peak
amplitude
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Amplitude/Loudness Examples The higher the peak amplitude of a sinusoidal sound, the
louder the sound seems to be.
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RMS amplitude
Peak-to-peak amplitude is sufficient for characterizingthe loudness of sinewaves, but speech sounds are more
complex.
Another method of measuring loudness:
root-mean-square (RMS) amplitude
To calculate RMS amplitude:
1. Square the pressure value of the waveform at each
point (sample) in the sound file
2. Average all the squared values
3. Take the square root of the average
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RMS example
pressure 1 0.707 0 -0.707 -1 -0.707 0 0.707 1
sample 1 2 3 4 5 6 7 8 9
A small sampling of a sinewave has the following
pressure values:
It looks like this (in Excel):
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RMS calculationspressure 1 0.707 0 -0.707 -1 -0.707 0 0.707 1
sample 1 2 3 4 5 6 7 8 9
To calculate RMS amplitude for this sound, first square the
values of each sample:
Then average all the squared values
(1 + .5 + 0 + .5 + 1 + .5 + 0 + .5 + 1) / 9 = 5/9 = .555
Then take the square root of the average
RMS amplitude = .745
square 1 0.5 0 0.5 1 0.5 0 0.5 1sample 1 2 3 4 5 6 7 8 9
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Another example What about the RMS amplitude of this sound wave?
It looks like this (in Excel):
pressure 1 1 1 -1 -1 -1 1 1 1
sample 1 2 3 4 5 6 7 8 9
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More Complex Waveforms The following waveforms all have the same peak-to-peak
amplitude:
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Intensity
Two related concepts are acoustic powerand intensity.
Poweris just the square of amplitude.
P = A2
The intensity of a sound is its power relative to the power of
some reference sound.
Intensity is usually measured in decibels (dB).
Decibels is a measure of intensity with reference to the
quietest sound human ears can hear.
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Some Numbers The intensity of a sound x can be measured in bels,
where a bel is defined as:= log10 (x
2 / r2)
r2 is the power of the reference sound
x2
is the power of sound x.
A decibel is a tenth of a bel.
Some typical decibel values:
30 dB Quiet library, soft whispers
40 dB Living room, refrigerator
50 dB Light traffic, quiet office
60 dB Normal conversation
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Numbers, continued
Some typical decibel values:
70 dB Vacuum cleaner, hair dryer
80 dB City traffic, garbage disposal
90 dB Subway, motorcycle, lawn mower
100 dB Chain saw, pneumatic drill
120 dB Rock concert in front of speakers, thunderclap
130 dB Pain threshold
140 dB Gunshot blast, jet plane
180 dB Rocket launching
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Intensity Interactions
Perceived loudness depends on frequency, as well asamplitude.
Mid-range frequencies sound louder than low or extremely
high frequencies.
100 Hz
250 Hz
440 Hz
1000 Hz
4000 Hz
10000 Hz
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An Interesting Fact
Some vowels are louder than others
dB of different vowels relative to (Fonagy, 1966):
: 0.0[e] : -3.6
[o] : -7.2
[i] : -9.7[u] : -12.3
Why?
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Another Interesting Fact
Some vowels are inherently longer than others.
Data from Swedish (Elert, 1964):
long shorthigh [i y u] 140 msec 95
mid 155 103
low 164 111
Why?
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Sonority
Loudness is also a highly context-dependent measure.
Can vary wildly within speaker, from speaker to
speaker, from room to room, and across speaking
contexts.
However, all things being equal, some speech sounds are
louder than others.
Course in Phonetics:The sonority of a sound is its loudness relative to that
of other sounds with the same length, stress and pitch.
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From Ladefoged
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A Sonority Scale
low vowels
high vowelsglides
liquids
nasals
fricatives
stops
high sonority
low sonority
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Sonority and Syllables
An old idea (e.g., Pike, 1943): syllables are organized
around peaks in sonority.
This is the Sonority Sequencing Principle (SSP).
Example: [bd] is a well-formed syllable in English.
[]
[b] [d]
high sonority
low sonority
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Sonority and Syllables
An old idea (e.g., Pike, 1943): syllables are organized
around peaks in sonority.
This is the Sonority Sequencing Principle (SSP).
Example: [blnd] works well, too.
[]
[l] [n]
[b] [d]
high sonority
low sonority
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Technical Terms
[]
[l] [n]
[b] [d]
high sonority
low sonority
sonority peak
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Technical Terms
The sonority peak forms the nucleus of the syllable.
[]
[l] [n]
[b] [d]
high sonority
low sonority
nucleus
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Technical Terms
The sonority peak forms the nucleus of the syllable.
The sounds that precede the nucleus form the syllable onset.
[]
[l] [n]
[b] [d]
high sonority
low sonority
onset
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Technical Terms
The sonority peak forms the nucleus of the syllable.
The sounds that precede the nucleus form the syllable onset.
The sounds that follow the nucleus form the syllable coda.
[]
[l] [n]
[b] [d]
high sonority
low sonority
coda
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Technical Terms The sonority peak forms the nucleus of the syllable.
The sounds that precede the nucleus form the syllable onset.
The sounds that follow the nucleus form the syllable coda.
Together, the nucleus and coda form the syllable rhyme.
[]
[l] [n]
[b] [d]
high sonority
low sonority
rhyme
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Some basic principles Onsets must rise in sonority towards the syllable peak.
Examples:
stop - {liquid/glide} play quick
fricative - {liquid/glide} fling thwack
[s] - {liquid/nasal/glide} slide snowsweet
What onset clusters should be ruled out?
Can you think of any English examples where this
principle might not work?
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Some basic principles Codas must drop in sonority away from the syllable peak.
Examples:
nasal - {fricative/stop} tenthhand
liquid - {fricative/nasal/stop} help helmheart
fricative - stop test
What coda clusters should be ruled out?
Can you think of any English examples where this
principle might not work?
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Other ProblemsThe Sonority Sequencing Principle doesnt always work.
How can we define a syllable?
An alternative idea: each syllable is a chest pulse
(Stetson, 1951)
It turns out this doesnt work, either.
Chest muscles dont necessarily contract for each
syllable (Ladefoged, 1967)
Any better ideas?