Speech Science VII

Acoustic Structure of Speech Sounds

WS 2007-8

Topics

• Subcategories of consonants – production and acoustic consequences.

• Spectral structure of consonants

• Reading: BHR, pp. 114-138Kent, pp. 350-362P.-M. pp. 114-132

Vowels vs. consonants

• Vowels all have a periodic glottal source (excitation)

• The filter is therefore the whole vocal tract

• Consonants can have (i) a periodic glottal source, or (ii) an aperiodic source (glottal or supraglottal) or (iii) a mixture of aperiodic supraglottal + periodic glottal

• Consonants with a periodic source alone are sonorants, those with an aperiodic source are obstruents, which can be voiceless or voiced (+ periodic source)

Sonorants

• Sonorants can be subdivided intoapproximant (vowel) glides ([])lateral approximants ([])Nasal stops ([m])

• Vowel glides have vocalic structure but are more constricted than vowels and there show less radiated energy (have lower intensity).

[] []; [] []; [] [];• Laterals and nasals have a divided resonator, which

causes resonances to cancel each other out “zeros” or “anti-resonances” = lack of resonance.

Sonorants: vowel glides: [j]

Vowel glides are defined acoustically by the formant change from vowel to cons. and back.N.B., [iji] shows very little formant movement: [i] [j]

Sonorants: vowel glides: [w]

[] has very reduced intensity because of lip-rounding.[] shows very strong formant movement: [] and [] are maximally different.

Sonorants: vowel glides: []

[] has a lower F2 than [j] because of lip-rounding but not as low as [w], which has both lip-rounding and a back tongue position.

Sonorants: liquids [l]

[r] & [l] are traditionally called “liquids” bcause of their soft sound. The lateral [l] has a resonating cavity divided by the tongue tip and blade, which causes “anti-resonances” – often around 2 kHz.

Sonorants: liquids []

has similar glide properties to vowel glides but the tongue shape is not vocalic (convex). The concave shape (raised tip) lowers F3 drastically.

Nasals 1

• Pharynx + Nasal tract = main resonator;Oral tract = side resonator

Nasals 2

The main resonator is constant; the side resonator varies (this affects the strength of the resonances).

Obstruents

• Obstruents are characterized by a turbulent source caused by constriction or the release of a closure somewhere in the vocal tract

• Plosives consist of a closure followed by a quick release, with a voicing delay (voiceless aspirated: []) or with voicing during the closure (voiced: []) or immediately after the release (voiceless unaspirated: [p, t, k])

• Fricatives are produced by forming a constriction: ([]).

• Affricates are a stop followed by a homorganic fricative: ([,]

Plosives

• The primary acoustic property of plosives is the lack of energy (or low periodic energy) during the closure period. This is similar for all places of articulation, but different for voiced and voiceless.

• The second important property (not present in all contexts) is the release noise (explosion), which stimulates the filter between the place of release and the lips and therefore reflects the place of articulation.

• The third property (not always present) are the formant transitions of the preceding and following vowel.

Plosives: acoustic differences

[] [] []

1. closure duration? 2. voicing in closure?

3. energy in burst? 4. formant transitions?

Plosives: acoustic differences 2

[] [] []

1. closure duration? 2. voicing in closure?

3. energy in burst? 4. formant transitions?

Plosives: acoustic differences 3

[] [] []

1. closure duration? 2. voicing in closure?

3. energy in burst? 4. formant transitions?

Fricatives

• We distinguish between fricatives with additional turbulence at the teeth (sibilants) and those without.

Model configuration for sibilant production

primary source of turbulence

source of secondaryturbulence

Sibilants without teeth!

If the teeth are missing, sibilants sound (and look) very different.

Other fricatives

• Fricatives without additional turbulence are:(labio-)dental []; palatal []; velar [];uvular []; pharyngeal and glottal [].

• From the (labio-)dental place of constriction (with almost no resonating cavity) to the glottal constriction (with the whole vocal tract as resonator), the size of the resonating cavity increases, producing lower-frequency resonances.

Other fricatives 2

sibilants{

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