Voice source characterisation

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Voice source characterisation

• Gerrit Bloothooft
• UiL-OTS Utrecht University

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Voice research

• To describe and model the properties of the
  vocal sound source from view points of
• Physiology
• Acoustics
• Perception

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Importance of the voice

• Speech synthesis
• Towards natural sounding synthesis
• Speech recognition
• Using source properties in recognition
• Speaker recognition/identification
• Voice source characteristics are essential
• Diagnosis
• Pathologies, voice classifications

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Voice possibilities

• Limited use of voice in speech
• Range of the fundamental frequency
• Vocal intensity range
• Spectral variation

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Focus in this presentation

• How do acoustic voice source characteristics
  vary as a functionof F0 and vocal intensity

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Voice profile measurement

• Thirties Intensity range as function of various
  pitches
• manual measurement
• Eighties Automatic computation ofF0 and
  Intensity
• computer measurement
• visual feedback
• additional parameters

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Measurement unit

• One decibel
• One semi-tone

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Measurement procedure

• Subject in front of computer screen
• Microphone on head set (30 cm)
• Just phonate, sing, and see the result
  immediately
• Best results with recording protocol
• Feed back stimulates extreme phonations

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Voice profile / density
Vocal Intensity (dB SPL)
Sample density
Fundamental frequency (Hz)
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Voice profile / speech area
Vocal Intensity (dB SPL)
Sample density
Fundamental frequency (Hz)
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Acoustic voice quality parameters

• Jitter
• Stability of periodicity
• Asymmetry in vocal folds
• Crest factor
• Max amplitude divided by average energy
• Relates to spectral slope
• Many more

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Crest factor
Vocal Intensity (dB SPL)
Crest factor
Fundamental frequency (Hz)
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(No Transcript)
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Real time presentation

• Screen presentation
• One data point per F0-I cell
• Advanced data storage new
• Full audio signal
• Full distribution of data per F0-I cell
• Data for screen presentation

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Advantages

• Reusability of recordings
• Statistical analysis per F0-I cell
• Study of time-varying behavior

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Crest factor
Vocal Intensity (dB SPL)
Crest factor
Fundamental frequency (Hz)
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Crest factor median smoothed
Median smoothing of crest factor
Vocal Intensity (dB SPL)
Crest factor
Fundamental frequency (Hz)
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Vocal Registers

• Different movement patterns of the vocal folds
• Pulse register (creaky voice)
• Modal register
• Falsetto register

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Pulse register

• Less than 50 Hz
• Irregular
• Long closed period

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Pulse register
Vocal Intensity (dB SPL)
Fundamental Frequency (Hz)
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Modal register

• Normal use of voice
• Active role of M. Vocalis
• Vocal folds thick and completely vibrating
• Wide range in F0 and intensity
• Flat spectrum

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Modal register
Vocal Intensity (dB SPL)
Fundamental frequency (Hz)
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Falsetto register

• Higher pitches
• M. Vocalis passive, tense vocal ligaments through
  M.Cricothyroidus
• Edge vibration of vocal volds
• Sound poor in higher harmonics (in untrained
  subjects)

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Falsetto register
Vocal Intensity (dB SPL)
Fundamental frequency (Hz)
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Register overlap
Vocal Inensity (dB SPL)
Fundamental frequency (Hz)
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Chest- en head voice

• Refer to secundary vibratory sensations in the
  body
• Chest voice loud modal register
• Head voice
• males higher, softer modal register in overlap
  area with falsetto register
• women falsetto register

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Chest voice and Head voice
chest
Vocal Intensity (dB SPL)
head
Fundamental frequency (Hz)
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Registers and voice profiles

• With a description using
• Iso-crest factor lines
• Iso-jitter lines

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Iso-crest factor lines
6 dB
Vocal Intensity (dB SPL)
Crest factor
4 dB
Fundamental frequency (Hz)
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Iso-jitter lines
Vocal Intensity (dB SPL)
Jitter ()
3
Fundamental frequency (Hz)
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New representation

• Areas defined by iso-parameter lines
• crest factor lt 4 dB
• crest factor gt 4 dB, lt 6 dB
• crest factor gt 6 dB
• jitter lt 3
• relative rise time lt 6

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Areas in the phonetogram
RRT lt 6 pressed-like
Crest factor lt 4 dB sine-like
Vocal Intensity (dB SPL)
Jitter gt 3, unstable
Fundamental frequency (Hz)
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Vocal registers in the phonetogram
Chest voice boundary
Vocal Intensity (dB SPL)
Falsetto upper boundary
Modal lower boundary
Fundamental frequency (Hz)
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Comparison of voice profiles

• Characterisation of
• Voice pathologies
• Voice classifications
• Reuse stored voice profiles of subjects with
  known voice history

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Important features

• Contour has limited value
• but most research goes into that direction (norm
  profiles)
• Distribution of acoustical parameters across the
  voice profile tells much more

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We need

• Unit for comparison
• Voice profile unit defined by small range of F0
  and Vocal Intensity
• Distributions of acoustic voice parameters per
  unit
• Probability density function per parameter
• Model
• Hidden Markov Model

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Unit model

• two unconnected states per phonetogram unit
• vocal registers
• start and end of phonetion

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Correspondences

• Speech Voice Profile
• phoneme model F0/I unit model
• not labeled labeled by F0 and I
• spectral envelope acoustic voice parameters
• language model unrestricted transitions
• forced alignment
• recognition

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Crest factor distributions
 
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Most distinctive states
Vocal Intensity (dB SPL)
Distinctiveness
Fundamental frequency (Hz)
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Conclusions

• Voice profiles can enhance our understanding of
  vocal behaviour in a visually attractive way
• Current data storage opens a series of important
  research topics
• Market opportunities for light versions