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Speech Science > Chapter 7 > Flashcards

Chapter 7 Flashcards

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1
Q

What is a vowel?

A

A vocal sound produced by relatively free passage of the airstream through the larynx and oral cavity

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2
Q

What is a consonant?

A

A speech sound produced with one or more areas of the vocal tract narrowed by some degree of constriction

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3
Q

What is another name for the acoustic theory of speech production?

A

The source filter theory

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4
Q

What does the source filter theory tell us?

A

The features of the vocal tract can be inferred from its acoustic output (so, specific articulatory postures produce specific sounds)

The speech production system may be broken down into two major components: the sound source and the filter, or resonator

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5
Q

Tell me about the source filter theory.

A

The source creates the sound rich in harmonic structure

The filter selects a portion of the harmonic frequencies to be radiated out of the mouth
- Frequency dependent
- The vocal tract resonates the source signal by allowing certain frequencies to pass through the filter with greater amplitude than other frequencies
- Characteristic resonances (formants): the frequencies that are selected for radiating out of the mouth

So the sound source provides the input to the vocal tract, and the resonator filters, or modulates, the sound

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6
Q

What is the spectral roll-off?

A

As you go up in harmonic frequency, each harmonic decreases in amplitude at a rate that is proportional to the inverse square of the harmonic number (referred to as the roll-off characteristic of the spectrum). The spectral roll-off of an actual glottal waveform may be very different from the triangular wave, but the roll-off (the decrease in amplitude of successively higher harmonics of the phonatory signal) will always decrease uniformly

It’s 12 dB per octave

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7
Q

What is the source spectrum?

A

The input energy for the acoustic resonator (the vocal tract)

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8
Q

Acoustic source characteristics…

A

The rate of vibration determines the fundamental frequency and the harmonic frequencies of the alternating compressions and rarefactions of each puff of air, but the way in which the harmonics are filtered depends upon the resonant characteristics of the vocal tract

The resonant frequencies of the vocal tract determine the vowel that is produced and contribute to the quality of the sound

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9
Q

What is a formant?

A

A concentration of energy around a particular frequency in the acoustic wave

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10
Q

What defines the resonant characteristics of the vocal tract?

A

The length and cross-section of the vocal tract

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11
Q

How does the overall length of the vocal tract effect the frequency location of the formants?

A
  • Shortening the vocal tract will raise the formant frequencies
  • Elongating the vocal tract will lower the formant frequencies
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12
Q

What is the difference between formants and harmonics?

A
  • Formants are resonating characteristics of the vocal tract and describe the acoustic filter
  • Harmonics are multiples of the fundamental frequency and describe the sound source
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13
Q

In the ideal triangular wave, for every octave (doubling of frequency), how much does the acoustic power increase?

A

It increases by a factor of 4/by 6 dB

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14
Q

Lip radiation:

A

The characteristics of this boundary are such that when the sound pressure wave exits the oral cavity, the higher-frequency harmonics are resonated more than the lower-frequency harmonics because the radiation characteristics at the lips favor the high-frequency components (air particle displacement is greater at frequencies with greater intensity. Lower frequencies and harmonics have greater intensity and therefore face more resistance from the atmosphere)

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15
Q

Does the vocal tract itself add energy?

A

The vocal tract does not add energy (it does not increase the amplitude of any specific harmonic), it only selectively allows a greater or lesser amount of the energy of each harmonic to be radiated out of the vocal tract

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16
Q

What lowers formant frequencies?

A

Increasin the length of the tube

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17
Q

What defines the formants of a tube?

A

The length and cross-section

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18
Q

What changes the frequency of the formant?

A

A constriction in the vocal tract at or near a node

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19
Q

What two rules govern the relationship between formant frequency and perturbation?

A

A constriction at or near an antinode, at which point the volume velocity is at a maximum and the pressure is at a minimum, lowers the frequency of the formant

A constriction at or near a node, at which point the volume velocity is at a minimum and the pressure is at a maximum, raises the frequency of the formant

From these two rules of perturbation, we can specify general relationships of vocal tract posture and formant frequencies

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20
Q

Because an antinode is always located at the opening of the lips:

A
  • All formants are lowered by labial constriction
  • Formants tend to be raised by lowering of the mandible
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21
Q

How is F1 influenced?

A

Influenced by oral cavity opening and by constriction in the lower pharynx, just above the glottis
- F1 is lowered by a constriction in the oral cavity near the point of maximum volume velocity
- F1 is raised by constriction in the pharynx

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22
Q

How is F2 influenced?

A

Most influenced by the shape of the posterior portion of the tongue
- F2 is lowered by a constriction in the area of the lips or at the back of the oral cavity in the oropharynx (u)
- F2 is raised by a constriction in the anterior oral cavity behind the lips (i)

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23
Q

How is F3 influenced?

A

Most influenced by the position of the tip of the tongue
- F3 is lowered by constriction at the lips and in the middle of the mouth (er)
- F3 is raised by a constriction in the oropharynx (a) and by constriction in the anterior mouth (j)

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24
Q

How are vowels classified?

A

By three dimensions of their vocal tract articulatory posture:
- tongue height
- tongue advancement
- lip rounding

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25
What are the corner vowels?
- The most extreme high vowels: /i, u/ - The lowest vowels: /ae, a/ - The most front vowels: /i, ae/ - The most back vowels: /u, a/
26
What are the five front vowels from high to low?
/i, I, e, E, ae/
27
What are the five back vowels from high to low?
/u, û, o, c, a/
28
What provides the acoustic representation of the vowel?
The relationship among the formant frequencies provides the acoustic representation of the vowel, which is what provides our perception of vowel quality
29
How does vowel height affect F1 and F2?
The frequency of the first formant appears to have an inverse relationship with vowel height; as the vowel becomes lower or more open, F1 increases - We state, therefore, that the frequency of the first formant inversely influences the perception of vowel height - The relationship of F2 and vowel height is less certain… for the front vowels, F2 decreases as the vowel becomes more open; for the back vowels, no clear relationship is apparent
30
How does tongue advancement affect F1 and F2?
The perception of vowel advancement is less straightforward - As the vowels move from back to front, F2 increases generally but not consistently - Lip rounding tends to lower the frequency of all formants - It is most likely that the perception of vowel advancement is a function of both F1 and F2 (as the first and second formant frequencies move closer together, the perception of back vowel quality increases)
31
What are the three emphasized features of a stylized spectrogram?
For the front vowels, the frequency locations of the first and second formants are generally spaced further apart, whereas the frequencies of the second and third formants are generally located close to each other - As the vowel quality moves forward, F1 and F2 become more separated - As the anterior space in the oral cavity becomes smaller and the resonance space of the posterior oral cavity widens, F1 and F2 become more separated - As we move to the back vowels, we note that F1 and F2 are located close to each other, whereas the frequencies of the second and third formants are generally located farther apart from each other; the perceptual vowel quality of backness is a function of the relationship of F1 and F2 For both the front and back vowels, F1 varies inversely with vowel height; vowel height decreases and F1 increases as we move from the high (close) front vowel /i/ to the low (open) front vowel /ae/ This graph of the frequencies of F1, F2, and F3 as a function of vowel is just the traditional vowel quadrilateral straightened out and laid flat
32
How does changing the size of the space affect resonance?
A smaller resonating space within the vocal tract vibrates at a higher frequency than a larger resonating space The larger resonating spaces will produce lower formant frequencies than the smaller resonating spaces
33
What is motor equivalence?
The ability of the individual to assume different articulatory postures to achieve the same acoustic output
34
Is the vocal tract a variable or invariable resonator?
The vocal tract is a variable resonator; the natural resonant frequencies of the vocal tract vary depending upon the vocal tract posture
35
What is a vowel space?
The set of F1-F2 points that specify each vowel
36
What are the tense vowels?
Those produced with greater muscle contraction than lax vowels Those produced at the extremes of articulatory posture, with the tongue higher in the oral cavity Six tense (long) vowels: i, e, er, er, u, o They are longer in duration
37
What are the lax/short vowels?
Five lax (short) vowels: I, uh, E, ou(ld), c Short vowels generally don’t appear in open syllables (syllables ending in a vowel) Shorter in duration
38
What are the neutral tenseness vowels?
Neutral tenseness vowels: ae, a, a
39
Tell me about rhotacization.
Rhotacization: the r-coloring of a vowel (describes an auditory perceptual quality of a vowel associated with /r/) - The “3r” occurs as the nucleus in a stressed syllable only - The “er” occurs as the nucleus of an unstressed syllable only
40
What are monophthongs?
Pure vowels (vowels produced with a constant vocal tract posture)
41
What is the defining feature of diphthongs?
Defining feature of diphthongs is that the articulatory posture shifts smoothly from the first vowel to the second one (if this smooth glide isn’t present, it’s not a diphthong)
42
What do diphthongs TEND to do?
Cannot be characterized by a single tongue height or advancement or lip rounding posture; but they tend to move from tense to lax, and the end up the diphthong is always high
43
What is an onglide?
The articulatory starting point
44
What is an offglide?
The ending of the articulation
45
Do vowels have an inherent or intrinsic pitch?
YEP
46
What are pure vowels?
Those in which the articulatory position and sound remain constant throughout production (except for the influence of adjacent sounds) /ee, ih, eh, ae, oo, ou, c, ah, uh, uh/
47
What are glided vowels?
Those in which small articulatory changes occur within their production /o, ay/
48
How many vowels does American English have?
American English contains approximately 14 or 15 vowels, plus the rhotacized vowels of /er, er/
49
How many vowels does Spanish have?
Spanish has only five vowels /ee, ay, ah, oh, oo/
50
What is accentedness?
The listener’s perception of how closely an individual’s speech approaches that of a native talker (native meaning someone who speaks a language or dialect from a very young age)
51
How is some energy lost during vocal production?
Some energy is lost to: - The lungs through the open vocal folds - The walls of the pharynx and mouth - Frictional forces result in a loss of energy between individual air particles
52
Are harmonics more widely distributed in the spectrum for men or women?
Harmonics from women are more widely distributed in the spectrum than men, because harmonics are integer multiples of the fundamental frequency, and women have higher pitch, resulting in wider-spaced harmonics
53
What are the three vocal tract effects on the VRP?
Over most frequencies, maximal intensity increases with f0 (because raising f0 is achieved through increasing vocal fold stiffness, and also because there’s increased lung pressure, which regulates intensity) - The vocal tract radiates acoustic power more efficiently as f0 is raised - At the very highest frequencies, the spectral content of the voice signal contains less energy, and so less incremental increase in intensity is obtained as f0 is raised further The vowel used to produce the VRP affects the overall contour of the plot - These contrasts are due to the differences in formant frequencies for the two vowels - When a harmonic is located far from a formant, the harmonic energy will be attenuated - The location of the harmonics depends upon the f0, and do for any given vowel, moving the f0 will affect which harmonics are located near a formant - This affects the smoothness of the upper contour of the VRP Slight irregularity of the upper contour (the ripple effect) - These ripples represent fluctuations in maximal intensity due to the effect of the vocal tract filter function interacting with the f0
54
What is formant/vocal tract tuning?
The process of increasing intensity when the f0 or one of its harmonics coincides with a formant frequency
55
What are the two characteristics of the formant that we refer to concerning location?
Center frequency and bandwidth
56
Acoustic filters and passing frequency components:
Certain frequencies will be attenuated (decreased in amplitude) to a relatively lesser degree than other frequencies Less attenuation means that more of the energy of the selected frequency component is allowed to be transmitted (it passes certain ones more effectively than others)
57
What are low-pass filters?
Block the high-frequency components of the wave and allow the low-frequency components to pass
58
What are high-pass filters?
Block the low-frequency components of the wave and allow the high-frequency components to pass
59
What is the frequency cut-off?
The delimiting frequency: the frequency below which all frequencies would be damped (not allowed to pass)
60
What is a bandpass filter?
A filter with both a low and a high-pass cutoff frequency
61
What is the half-power point?
The acoustic energy attenuation point where no more frequency components pass
62
What is the cutoff frequency defined as?
The frequency at which the amplitude of the frequency component is decreased by 3 dB (half its power)
63
What kind of filters do formants act as?
Formants act as bandpass filters - Center frequency: the midpoint or peak of the filter; it represents the frequency that is allowed to pass with the greatest amplitude - Bandwidth: the range of frequencies between the low and high-pass cutoff frequencies; it specifies the range of frequencies that are allowed to pass
64
What is sound spectrography (sonography)?
The graphic representation of the frequency and intensity of the sound pressure wave as a function of time
65
What are the two types of spectrograms?
- A narrow bandwidth resolves frequency information well but has poor time resolution - A wide bandwidth resolves frequency information poorly but the time resolution is good A spectrogram may present detailed information about the harmonic structure of the source signal or precise information about the resonant characteristics of the vocal tract; they cannot by displayed at the same time because time and frequency are inversely related
66
Tell me about narrowband spectrograms.
- The gray scale represents intensity, so darker harmonics contain more energy - Lower harmonics contain more energy - Harmonic energy is attenuated what it does not coincide closely with a formant frequency
67
Tell me about wideband spectrograms.
- Individual harmonics are not resolved clearly - Broader bands of energy are evident (spectral peaks - they’re associated with the vocal tract formants) Has vertical striations, which are representative of the glottal pulses As the f0 is raised, the vertical striations move closer together, because they’re representative of the glottal pulses, which get faster as frequency increases - Formant location does not change - Raising the f0 does not change the vowel, because the vocal tract articulatory posture remained constant
68
What resolutions do each type of spectrogram present?
Narrowband filtering provides good resolution of the harmonic (frequency) structure of the source signal Wideband filtering provides good time resolution of the glottal pulses and formant structure of the vocal tract
69
Where are the formants for front vowels?
F1 and F2 are further apart, and F2 and F3 are closer
70
Where are the formants for the back vowels?
F1 and F2 are closer together, and F2 and F3 are farther apart
71
What are rhotacized vowels characterized by?
A very low F3
72
What is the long-term average spectrum (LTAS)?
An averaging of the spectral energy over a window of a specified duration of sustained vowel phonation Has been used to assess overall perceived intelligibility of speakers and voice quality
73
What is noise?
The energy between the harmonics
74
What is the harmonics-to-noise ratio (H/N)?
A numerical evaluation of the ratio of the energy in the fundamental and harmonics to the energy in the aperiodic or noise component of the speech signal, averaged over several cycles A typical H/N for healthy speakers averaged 11.9 dB
75
What is cepstral analysis?
It’s a Fourier transform of the power spectrum that shows the extent to which the f0 and harmonic structure stand out from the background noise The dominant cepstral peak reflects the periodicity and energy in the voice signal; the greater the periodicity and the higher the energy, the greater the amplitude of the dominant cepstral peak Does not rely upon identification of individual vibratory cycles, so it’s valid even when the vocal signal is not periodic Can be used as an objective measure of vocal quality
76
What is inverse filtering?
An estimate of the glottal flow signal from the speech signal

Speech Science (12 decks)

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