Transcript Speech Science VII - uni

WS 2007-8
Speech Science VII
Acoustic Structure of Speech Sounds
Topics
• Subcategories of consonants – production and
acoustic consequences.
• Spectral structure of consonants
• Reading: BHR, pp. 114-138
Kent, pp. 350-362
P.-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 into
approximant (vowel) glides ([w, j,
])
lateral approximants ([l, , ])
Nasal stops ([m, n, , N])
• Vowel glides have vocalic structure but are more
constricted than vowels and there show less radiated
energy (have lower intensity).
[w]  [u];
[j]  [i];
[]  [y];
• 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]
a
j
i
a
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]
a
w
i
a
w
[w] has very reduced intensity because of lip-rounding.
[iwi] shows very strong formant movement: [i] and
[w] are maximally different.
Sonorants: vowel glides: []
a

i
a

[] 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]
A
l
i
A
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 []
A

i

i
A
[] 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:
[p, t, k]) or with voicing during
the closure (voiced: [b, d, g]) or
immediately after the release (voiceless
unaspirated: [p, t, k])
• Fricatives are produced by forming a constriction:
([f, v, s, z, S, Z, C,
, x, , X, ]).
• Affricates are a stop followed by a homorganic
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
[a
b
1. closure duration?
3. energy in burst?
[a
a]
p
[a
a]
2. voicing in closure?
4. formant transitions?
p
Plosives: acoustic differences 2
[a
d
1. closure duration?
3. energy in burst?
[a
a]
t
[a
a]
2. voicing in closure?
4. formant transitions?
t
Plosives: acoustic differences 3
[a
g
1. closure duration?
3. energy in burst?
[a
a]
k
[a
2. voicing in closure?
4. formant transitions?
a] k
Fricatives
• We distinguish between fricatives with additional
turbulence at the teeth (sibilants) and those without.
primary source source of secondary
of turbulence turbulence
Model configuration for sibilant production
Sibilants
without
teeth!
If the
teeth are
missing,
sibilants
sound (and
look) very
different.
Other fricatives
• Fricatives without additional turbulence are:
(labio-)dental [f, v, T, D]; palatal
[C, ]; velar [x, ];
uvular [X, ]; pharyngeal [, ] and
glottal [h, ].
• 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 lowerfrequency resonances.
Other fricatives 2
[f] [T] [s]
[S] [C]
sibilants
[x]
[] [h]
A competition
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