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Sensation and Perception

Chapter 12: Speech and Music

Lecture Outline

• Speech – Phonemes – Production of phonemes

• Vocal system • Filtering • Formants • Spectrogram • Voicing • Point of articulation • Manner of articulation

– Perceiving phonemes • Correspondence • Segmentation • Categorical perception • McGurk effect

– Neural basis of production and perception

• Music – Dimensions of music

• Pitch • Loudness / dynamics • Timing / rhythm

– Melody – Consonance and

dissonance – Neural basic of music

perception – Absolute pitch – Amusia

Production of Phonemes

• Phonemes

Production of Phonemes

• Speech consists of multiple harmonics

• The harmonics are filtered (changed) by the vocal folds and structures in the oral and nasal cavities (the filter is indicated as the red line)

• The peaks in the filtered sound (F1, F2, F3) are called formants

Formants for Vowels

• The oral cavity has a different shape when saying “bead” vs. “bad”

• The different shape results in different filtering of the sound

• The formants, F1, F2, and F3 have different frequencies for the two vowel sounds

Sound Spectrogram

Production of Consonants

• Voicing

• Point of articulation

• Manner of articulation

Patterns of Articulation Manner of Articulation; Voicing

Place of Articulation

Stops Fricatives Affricates Nasals Approximants

Voiceless Voiced Voiceless Voiced Voiceless Voiced Voiceless Voiced Voiceless Voiced

Bilabial /p/ pit

/b/ bit

/m/ Sum

Labiodental /f/ fine

/v/ vine

Dental /θ/ thick

/ð/ them

Alveolar /t/ tip

/d/ dip

/s/ sip

/z/ zip

/n/ sun

/l/ let

Postalveolar /ʃ/ ship

/3/ vision

/tʃ/ chip

/d3/ jet

/r/ rip

Palatal /j/ yet

Velar /k/ kit

/g/ get

/ŋ/ sing

Glottal /h/ hit

Perceiving Speech Sounds

• Perceiving speech is difficult because

– There is no one- to-one correspondence

between speech sounds and phoneme

– Segmentation problem

Coarticulation

Categorical Perception of Speech Sounds

-10 -5 0 +5 +10 +15 +20 +25 +30 +35 +40 +45 +50

McGurk Effect

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Top-Down Processes in Speech Perception: Word Segmentation

• If there are no physical pauses between words in normal speech, how do we segment speech into individual words

• New word starts when the next phoneme is unlikely to be part of the current word

– Phoneme transition probabilities -- within a word, some phonemes frequently follow others -- /th/ is often followed by /e/, and some phonemes rarely follow others -- /th/ is rarely followed by /q/

Top-Down Processes in Speech Perception: Phonemic Restoration

• When speech is interrupted by another sound, say a cough, one or phonemes may be covered by the sound. Yet, the perception of the phonemes occurs

– Phoneme transition probabilities often dictate that only a small number of phonemes are likely to have occurred during the sound and the missing phoneme is perceptually filled in.

Speech Perception and Production

Dimensions of Music: Pitch

• Octave – a range of notes such that the fundamental frequency of the last note is twice that of the first note

• Semitone – each octave is divided into 13 notes (including both end notes) separated by proportionally equivalent intervals

Pitch Helix

• The proportional equivalence of semitones is based on two perceptual observations:

– Notes an octave apart are perceptually more similar than notes that more similar frequencies

– The perceptual spacing of adjacent semitones is equal even though the frequency separation of

adjacent semitones is not equal (they are proportionately equal)

• Tone chroma and tone height

Dimensions of Music: Loudness and Timing

• Dynamics – the way the loudness of the notes changes as a piece of music progresses

• Rhythm – the temporal pattern of notes in music

– Fast tempo ≈ joyful mood (allegro is Italian for joyful)

– Slow tempo ≈ somber mood

Melody

• Melody – a sequence of notes arranged in a particular temporal pattern

– Relative position (number of semitones above or below the previous note) of pitches in the sequence

– Transposition – a version of a melody that starts at a different note but retains the relative position of all notes

• Six month old infants recognize transpositions as the same melody

Consonance and Dissonance

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524

786

1048

1310

1572

1834

2096

2358

392

784

1176

1568

1960

2352

D♭

277

554

831

1108

1385

1662

1939

2216

2493

Neural Basis of Music Perception

Absolute Pitch Perception

• Absolute pitch -- about 1% of the population can accurately name isolated notes

• Amusia – about 4% of the population have a profound impairment in perceiving and remembering melodies and in distinguishing melodies