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Syllables and Stress. October 25, 2010. Practicalities. Some homeworks to return… Review session on Wednesday. Mid-term on Friday. Note: transcriptions have been posted to the course web page. Let’s check out the Boston English sample. Review: Suprasegmentals.

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syllables and stress
Syllables and Stress

October 25, 2010

practicalities
Practicalities
  • Some homeworks to return…
  • Review session on Wednesday.
  • Mid-term on Friday.
  • Note: transcriptions have been posted to the course web page.
  • Let’s check out the Boston English sample.
review suprasegmentals
Review: Suprasegmentals
  • Last time, we learned that there were three kinds of languages:
  • 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)

    • it’s complicated
what is stress
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
loudness
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

amplitude loudness examples
Amplitude/Loudness Examples
  • The higher the peak amplitude of a sinusoidal sound, the louder the sound seems to be.
rms amplitude
RMS amplitude
  • Peak-to-peak amplitude is sufficient for characterizing the loudness of sinewaves, but speech sounds are more complex.
  • Another method of measuring loudness:
    • root-mean-square (RMS) amplitude
  • To calculate RMS amplitude:
    • Square the pressure value of the waveform at each point (sample) in the sound file
    • Average all the squared values
    • Take the square root of the average
rms example
RMS example
  • A small sampling of a “sinewave” has the following pressure values:
  • It looks like this (in Excel):
rms calculations
RMS calculations
  • 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
another example
Another example
  • What about the RMS amplitude of this sound wave?
  • It looks like this (in Excel):
more complex waveforms
More Complex Waveforms
  • The following waveforms all have the same peak-to-peak amplitude:
intensity
Intensity
  • Two related concepts are acoustic power and intensity.
  • Power is 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.
some numbers
Some Numbers
  • The intensity of a sound x can be measured in bels, where a bel is defined as:
    • = log10 (x2 / 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
numbers continued
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
intensity interactions
Intensity Interactions
  • Perceived loudness depends on frequency, as well as amplitude.
  • Mid-range frequencies sound louder than low or extremely high frequencies.
  • 100 Hz
  • 250 Hz
  • 440 Hz
  • 1000 Hz
  • 4000 Hz
  • 10000 Hz
an interesting fact
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?
another interesting fact
Another Interesting Fact
  • Some vowels are inherently longer than others.
  • Data from Swedish (Elert, 1964):
  • long short
  • high [i y u] 140 msec 95
  • mid 155 103

low 164 111

  • Why?
sonority
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.”
a sonority scale
A Sonority Scale
  • low vowels
  • high vowels
  • glides
  • liquids
  • nasals
  • fricatives
  • stops

high sonority

low sonority