Syllables and Stress, part II

March 3, 2014

Where Things Stand• Your mid-terms are still being graded.

• Your first production exercises are, too.

• The mid-terms will hopefully be back by Wednesday…

• And the production exercises some time after that.

• For the next couple of weeks, we’ll be focusing on acoustics.

• Note: acoustics is hard.

• The final exam has been scheduled!

• Tuesday, April 29th, 3:30 – 5:30 pm

• Location TBA

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• 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• 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• 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• 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• 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?

Frequency and Vowels• In the mystery tone language exercise, you may have noticed that the fundamental frequency of [i] was slightly higher than that of [a], for the same tones

“Intrinsic” Pitch• It’s been observed that F0 is usually higher for high vowels than for low vowels

[i] 183 Hz

[e] 169

[æ] 162

[a] 163

[o] 170

[u] 182

• Data from Lehiste & Peterson (1961) for American English

• The “Tongue Pull” Hypothesis (Honda, 2004):

• Raising the tongue for high vowels also raises the larynx

• The cricoid cartilage rises up and around the spine…

• Thus stretching the vocal folds

• and increasing longitudinal tension.

An Intrinsic Summary High Vowels Low Vowels

Intensity Less More

Duration Shorter Longer

F0 Higher Lower

• A word of caution:

• All of these factors (intensity, duration, F0) factor into perceived prominence and stress.

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.”

From Ladefoged

A Sonority Scale

low vowels

high vowels

glides

liquids

nasals

fricatives

stops

high sonority

low sonority

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: [bæd] is a well-formed syllable in English.

[æ]

[b] [d]

high sonority

low sonority

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: [blænd] works well, too.

[æ]

[l] [n]

[b] [d]

high sonority

low sonority

Technical Terms

[æ]

[l] [n]

[b] [d]

high sonority

low sonority

sonority peak

Technical Terms• The sonority peak forms the nucleus of the syllable.

[æ]

[l] [n]

[b] [d]

high sonority

low sonority

nucleus

Technical Terms• The sonority peak forms the nucleus of the syllable.

• The sounds that precede the nucleus form the syllable onset.

[æ]

[l] [n]

[b] [d]

high sonority

low sonority

onset

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.

[æ]

[l] [n]

[b] [d]

high sonority

low sonority

coda

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.

[æ]

[l] [n]

[b] [d]

high sonority

low sonority

rhyme

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’ ‘snow’ ‘sweet’

• What onset clusters should be ruled out?

• Can you think of any English examples where this principle might not work?

Some basic principles• Codas must drop in sonority away from the syllable peak.

Examples:

nasal - {fricative/stop} ‘tenth’ ‘hand’

liquid - {fricative/nasal/stop} ‘help’ ‘helm’ ‘heart’

fricative - stop ‘test’

• What coda clusters should be ruled out?

• Can you think of any English examples where this principle might not work?

Other Problems• The Sonority Sequencing Principle doesn’t always work.

• How can we define a “syllable”?

• An alternative idea: each syllable is a “chest pulse” (Stetson, 1951)

• It turns out this doesn’t work, either.

• Chest muscles don’t necessarily contract for each syllable (Ladefoged, 1967)

• Any better ideas?

Interesting Patterns• Check out the following words:

Atlantic atrocious

America arcade

astronomy arthritic

• When is the first vowel a ?

• Is there a difference between the /t/ in ‘atrocious’ and the /t/ in ‘Atlantic’?

• Why?

Syllables “defined”• “Syllables are necessary units in the organization and

production of utterances.” (Ladefoged, 1982)

• The construct of a “syllable” can account for a variety of interesting phonological patterns:

1. Vowel reduction in unstressed syllables in English.

2. Fricatives and stops devoice at the end of syllables in German, Russian (and many other languages)

3. Place contrasts disappear in coda position in Japanese (and many other languages)

4. Voiceless stops are aspirated at the onset of stressed syllables in many Germanic languages.

Back to Stress• Stress is a suprasegmental property that applies to whole syllables.

• Stressed syllables are higher in pitch (usually)

• Stressed syllables are longer (usually)

• Stressed syllables are louder (usually)

• Stressed syllables reflect more phonetic effort.

• The combination of these factors give stressed syllables more prominence than unstressed syllables.

Stress: Pitch

(N)

Complicating factor: pitch tends to drift downwards at the end of utterances

(V)

Stress: Intensity

(N)

(V)

Perception of stress is highly correlated with the area under the intensity curve

“Phonetic Effort”• Voiceless stops are more aspirated at the onset of

stressed syllables in English

• Vowels are often reduced to in unstressed syllables in English.

• There is less coarticulation across syllable boundaries in stressed syllables.

• X-Ray microbeam study (deJong et al., 1993); two utterances:

1. I said put the TOAST on the table, not the napkins!

2. I said PUT the toast on the table, don’t throw it!

X-ray microbeam data

Varying Levels of Stress/Prominence

• English has both primary and secondary stress.

• Example: “exploitation”

vowel X X X X

full vowel X X X

stress X X

tonic accent X