Task 9: Speech Perception Flashcards
What produces speech sounds?
position/movement of structures in vocal apparatus
Acoustic signal
pressure changes in air
Respiration
To generate an acoustic signal, air is pushed up from lungs past vocal cords and into vocal tract
Phonation
Process through which vocal folds are made to vibrate when air pushes out of lungs. In fact, sound depends on shape of vocal tract as air is pushed through.
Articulation
Shape of vocal tract is altered by moving articulators
Articulators
Tongue, lips, teeth, jaw and soft palate.
Resonance characteristics
Changing size and shape of space through which sound passes increases and decreases energy at different frequencies
How are vowels produced?
- Produced by vibration of vocal cords.
- Specific sounds of each cord are created by changing shape of vocal tract. By changing it, resonant frequency of vocal tract changes, producing peaks of pressure at different frequencies, called formants (F1 formant has highest frequency, F2 has next highest and so on)
How are consonants produced?
- Produced by closing of vocal tract.
- Movement of tongue, lips and other articulators create patterns of energy in acoustic signal. Rapid shifts in frequency before or after formants (vowels) are called formant transitions and are associated with consonants (T1, T2).
Sound spectrogram
Three-dimensional display that plots time on horizontal axis, frequency on vertical axis and amplitude (intensity) on color, with redder showing greater intensity, or gray scale.
- indicates patterns of frequencies and intensities that make up acoustic signal
Phoneme
the shortest segment of speech that, if changed, changes meaning of word.
What kind of relationship is between a phoneme and acoustic signal?
variable
Coarticulation
the articulation of two or more speech sounds together, so that one influences the other.
Perceptual constancy
We perceive sound of phoneme as same even if acoustic signal is changed by coarticulation.
Discuss variability from different speakers x2
- Individual differences – Some voices are high-pitched, other low-pitches, some talk rapidly, others slowly.
- Sloppy pronunciation – When in conversational speech, people sometimes do not articulate each word individually.
Name 3 ways speech perception systems deals with this variability problem in different ways (perceiving phonemes)
- categorical perception
- information provided by face/audiovisual speech perception
- information from our knowledge of language
Categorical perception (perceiving phonemes)
For speech and other complex sounds and images, it occurs when stimuli that exist along continuum are perceived as divided into discrete categories.
Voice onset time (categorical perception)
Time delay between when sound begins and when vocal cords begin vibrating.
Example: /da/ has a short VOT and /ta/ has a long.
Phonetic boundary (categorical perception)
Cross-over point from perception of one phoneme to another, depending on VOT.
Name and explain 2 qualities defining categorical perception
- Sharp labeling function – Small changes to simple acoustic stimuli (pure tones) leads to gradual changes in people’s perception of these stimuli.
- > when VOT goes above 35ms, perception from /da/ changes to /ta/. - Discontinuous discrimination performance – Two stimuli with VOTs on same side of phonetic boundary (25ms) are judged to be same (= perceptual constancy), whereas two stimuli on different sides of phonetic boundary are judged to be different.
- > If we did not have perceptual constancy we would perceive different sounds every time we changed VOT.
Information provided by face/audiovisual speech perception (perceiving phonemes)
Speech perception is multimodal, meaning that our perception of speech can be influenced by information from a number of different senses.
McGurk Effect
Effect illustrating that although auditory information is major source of information for speech perception, visual information can also exert strong influence on what we hear (= audiovisual speech perception).
When someone perceives someone talking i.e. their face what area is also activated
FFA
Information from our knowledge of language
Research showed that it is easier to perceive phonemes that appear in meaningful context.
