11Music and Speech Perception Chapter 11 11 Music and Speech Perception Music Speech 11 Music Music as a way to express thoughts and emotions Pythagoras: Numbers and musical intervals Some clinical psychologists practice music therapy
11 Music Musical notes Sounds of music extend across frequency range: 25 4200 Hz. 11 Music Octave: The interval between two sound frequencies having ratio of 2:1 Example: Middle C (C4) has fundamental frequency of 261.6 Hz; notes that are one octave from middle C are 130.8 (C3) and 523.2 (C5). There is more to musical pitch than just frequency! 11 Music Tone height: A sound quality whereby a sound is heard to be of higher or lower pitch; monotonically related to frequency Tone chroma: A sound quality shared by tones that have the same octave interval Musical helix: Can help visualize musical pitch
11 Music Musical instruments: Produce notes below 4 khz. Listeners: Great difficulty perceiving octave relationships between tones when one or both tones are greater than 5 khz. 11 Music Chords: Created when three or more notes are played simultaneously Consonant or dissonant Consonant: Have simple ratios of note frequencies Dissonant: Less elegant ratios of note frequencies 11 Music Cultural differences Research on music perception: Western vs. Javanese Javanese culture: Fewer notes within an octave; greater variation in note s acceptable frequencies Even young infants can learn to distinguish sounds in their native scale
11 Music Melody: An arrangement of notes or chords in succession. Examples: Twinkle, Twinkle Little Star, Baa Baa Black Sheep. Not a sequence of specific sounds: Sensitive to change, (i.e., change in octave). Notes and chords vary in duration: Tempo; fast or slow. 11 Music Rhythm: Not just in music! Lots of activities have rhythm: Walking, waving, finger tapping, etc. Bolton (1894): Experiments with sequence of identical sounds, perfectly spaced in time, but no rhythm; listeners reported hearing first sound of group as accented, while the rest remained unaccented. More examples: Car, train rides. Syncopated auditory polyrhythms : When different rhythms are overlapped. 11 Dominant Rhythm
11 Music Melody development 8-month olds: Able to learn new melodies 7-month olds: Can associate particular movements with particular melodies The Vocal Tract: The airway above the larynx used for production of speech. Includes the oral tract and nasal tract Humans are capable of producing lots of different speech sounds. 5000 languages spoken today, utilizing over 850 different speech sounds. Flexibility of vocal tract: Important in speech production. 11 The Basic Components of Speech Production (Part 1)
11 The Basic Components of Speech Production (Part 2) Speech Production Respiration (lungs) Phonation (vocal cords) Articulation (vocal tract) Respiration and phonation Initiating speech: Diaphragm pushes air out of lungs, through trachea, up to larynx. At larynx: Air must pass through two vocal folds. Children: Few vocal cords, high-pitched voices. Adult men: Larger mass of vocal cords, low-pitched voices.
Articulation Area above larynx: Vocal tract. Humans have ability to change shape of vocal tract by manipulating jaw, lips, tongue, body, tongue tip, velum. Manipulations: Articulation. Resonance characteristics. 11 Sound from Vocal Folds Peaks in speech spectrum: Formants Labeled by number, from lowest to highest (F1, F2, F3) concentrations in energy occur at different frequencies, depending on length of vocal tract. For shorter vocal tracts (children, short adults): Formants are at higher frequencies than for longer vocal tracts. Spectrogram.
11 Sound Spectrogram 11 Vowel Sounds of English Classifying speech sounds Sound: Most often described in terms of articulation. Place of articulation: (e.g., at lips, at alveolar ridge, etc.). Voicing: Whether cords are vibrating, not vibrating. English: Only small sample of sounds used by languages around the world; a lot more sounds are used!
Speech perception Speech production: Very fast. Experienced talkers: Coarticulation; attributes of successive speech units overlap in articulatory or acoustic patterns. Example: Say the word moody a few times, observe what happens to tongue. Computer programs: Very limited in recognizing speech. Categorical perception How do 2-year-olds do it? Research on acoustic cues used to distinguish different speech sounds. Categorical perception : Sharp labeling (identification), discontinuous discrimination, predictability of discrimination. How special is speech? Motor theory of speech perception: Special mechanisms just for perceiving speech Problems for motor theory: Speech production is just as complex, so speech perception complexity must be result of this complexity
How special is speech? Nonhuman animals can learn to respond to speech signals in similar way to human listeners Categorical speech perception: Not limited to speech sounds; also includes musical intervals; other categorical perceptions: faces, facial expressions 11 Categorical Perception Coarticulation and spectral contrast Research: How speech perception is explained by general ways that hearing, and perception works Example: Perception of coarticulated speech; explained by some fundamental ways of auditory system Contrast effects: Melodies are defined by changes between adjacent notes; spectral contrast helps listeners perceive speech
Using multiple acoustic cues Perception depends on experience. Comparison with face recognition. Learning to listen Babies learn to listen even before they are born! Prenatal experience: Newborns prefer hearing their mother s voice over other women s voices. Research of babies in France. Becoming a native listener Sound distinctions specific to various languages. Example: r and l are not distinguished in Japanese. Infants begin filtering out irrelevant acoustics long before they start to say speech sounds.
Learning words How do we know where one word ends and another begins? Research (Saffran et al.): Novel language with infants; can learn to distinguish words from nonwords after two minutes. Statistical learning. Speech in the Brain Brain damage follows patterns of blood vessels, not brain function, so difficult to study. PET and fmri studies: Help to learn about speech processing in brain. Listening to speech: Left and right superior temporal lobes are activated more strongly in response to speech than to nonspeech sounds. Some challenges in creating good controls for experiments. Categorical perception tasks. How do processes of hearing and speaking interact?