Acoustic Phonetics How to read spectrograms

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Acoustic PhoneticsHow to read spectrograms
Credits Bert Vaux, UW-Milwaukee Andrew
Faulkner, University College London
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Acoustic Phonetics

• Spectrogram Basic
• Spectral Cues
• Vowels
• Consonants
• Continuous Speech
• Epilogue

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I. Spectrogram Basics
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Source-Filter Theory of Speech Production
Source
Filter
Speech

• Speech production can be divided into two
  independent parts
• Source of sound, such as the larynx
• Filters that modify the source, such as the vocal
  tract

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Spectrograms
Spectrograms of "hee" "ha" and "who".
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Spectrograms
X-axis (horizontal) Time (milliseconds) Y-axis
(vertical) Frequency (Hertz) Z-axis (3-d
basically, coming right toward you) Amplitude
--gt amplitude corresponds to signal strength,
perceived as volume/loudness higher amplitudes
show up as darker marks on the spectrogram
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Fundamental Frequency

• measure of vocal fold vibration (Hz)
• Hz hertz cycles per second
• Males 120 Hz
• Females 255 Hz
• Children 265 Hz

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II. Spectral Cues

• Vowels
• Consonants

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A. Vowels

• Produced with no significant constriction of oral
  tract
• Articulations change resonances of the vocal
  tract
• Moving the tongue, lips and jaw change the shape
  of the vocal tract
• Resonances of the vocal tract are called formants
• Changing the shape of the vocal tract changes the
  
• formant frequencies

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Vowels Formants
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Vowels Formants
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Vowels Formants
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Vocal Folds
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The Vocal Folds in Action(very slow motion)
http//www.humnet.ucla.edu/humnet/linguistics/faci
liti/demos/demos.html
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Fundamental Frequency

• measure of vocal fold vibration (Hz)
• Hz hertz cycles per second
• Males 120 Hz
• Females 255 Hz
• Children 265 Hz

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Vowels Formants
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B. Consonants

• Stops
• Voicing
• Aspiration
• Nasals
• Fricatives
• Voicing
• Approximants
• (liquids and glides)

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1. Stops (e.g., /b/,/p/,/d/,/t/,/k/,/g/)

• Complete closure of the vocal tract
• Blocks flow of air through the oral cavity
• During voiced stops, only a voice bar can be
  produced during the closure

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Stops Voice Bar
idi
Voice Bar
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Stops (e.g., /b/,/p/,/d/,/t/,/k/,/g/)

• Complete closure of the vocal tract
• Blocks flow of air through the oral cavity
• During voiced stops, only a voice bar can be
  produced during the closure
• Burst created at consonant release
• Created as closure is partially opened
• Frication noise created by blowing air through
  partial opening
• Very short duration

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Stops Burst
idi
Burst
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Stops Voicing

• Voiced Consonants
• Voicing starts less than about 30 ms after
  release
• Voicing can occur during closure

• Unvoiced Consonants
• Voicing starts more than about 50 ms after
  release
• Voicing cannot occur during closure

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Stops Voicing
AtA vs. AdA?
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Stops Voicing
AdA
AtA
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Voicing and Aspiration

• Voiced Consonants
• Voicing starts less than about 30 ms after
  release
• Voicing can occur during closure

• Unvoiced Consonants
• Voicing starts more than about 50 ms after
  release
• Voicing cannot occur during closure

• Duration between release (i.e. burst) and start
  of voicing is
• called Voice Onset Time (VOT).
• long VOT gt aspiration

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Stops Aspiration
AdA
AtHA
Aspiration
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American English Aspiration
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2. Nasals (e.g., /m/, /n/)

• Similar to voiced stops, except air also flows
  through nasal cavity

• Velum controls airflow through nasal cavity
• Airflow allows voicing to continue during closure
• Stoppage of airflow in oral tract results in
  decreased energy, characterized by nasal zeroes
  (regions of extremely low energy)

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Nasals
/ana/ vs. /ada/?
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Nasals
ada
ana
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3. Fricatives (e.g., /s/,/z/,/f/,/v/)

• Created by forcing air through a small
  constriction
• Noise is produced due to turbulence

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Fricatives
afa
asa
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Voiced Fricatives (e.g., /z/,/v/)

• Vocal folds can vibrate at the same time that
  fricative energy is produced
• Creates a voice bar during the fricative

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Voiced vs. Voiceless Fricatives (1)
/T/ vs. /D/?
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Voiced vs. Voiceless Fricatives (1)
aTa
aDa
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Voiced Vs. Voiceless Fricatives (2)
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Voiced Vs. Voiceless Fricatives (3)
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Approximants (e.g., /l/,
/r/, /j/, /w/)

• More open constriction than for fricatives
• Free flow of air produces no turbulence
• Voicing continues during consonant

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Approximants (e.g., /l/, /r/, /j/, /w/)

• More open constriction than for fricatives
• Free flow of air produces no turbulence
• Voicing continues during consonant
• Similar to vowels
• Approximants have lower F1 than for vowels
• Glides tend to have more formant movement than
  vowels

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Approximants
awa
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Continuous Speech
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Continuous Speech
Im an idiot
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Continuous Speech
ajm n Idijt
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Continuous Speech, Segmented
a
a
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Summary of Spectral Cues

• Vowels (open oral tract)
• identified using formant structure (esp. F1 and
  F2)
• Consonants (differing degrees of constriction in
  the oral tract)
• Stops stoppage of air voice bar aspiration
• Nasals vowel-like, with nasal zeros
• Fricatives noise
• Approximants vowel-like formant movement

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IV. Epilogue
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Broad vs. Narrow Transcription
lta teegt lta rheegt
Broad tij rij
Narrow tHij rij
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Broad vs. Narrow Transcription
lta teegt lta treegt lta churchgt
Broad tij trij
tSrtS
Narrow tHij tSrij
tSrtS
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l "clean" vs. "lean"
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l "clean" vs. "lean"
klijn
lijn
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"Stoughton"
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"Stoughton"
stHo?n

stHow?n