Voice source characterisation Gerrit Bloothooft UiL-OTS Utrecht University

Emasters School Leuven 2002Voice Source Characterization2 Voice research To describe and model the properties of the vocal sound source from view points of: –Physiology –Acoustics –Perception

Emasters School Leuven 2002Voice Source Characterization3 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

Emasters School Leuven 2002Voice Source Characterization4 Voice possibilities Limited use of voice in speech Range of the fundamental frequency Vocal intensity range Spectral variation

Emasters School Leuven 2002Voice Source Characterization5 Focus in this presentation How do acoustic voice source characteristics vary as a function of F 0 and vocal intensity

Emasters School Leuven 2002Voice Source Characterization6 Voice profile measurement Thirties: Intensity range as function of various pitches –manual measurement Eighties: Automatic computation of F 0 and Intensity – computer measurement – visual feedback – additional parameters

Emasters School Leuven 2002Voice Source Characterization7 Measurement unit One decibel One semi-tone

Emasters School Leuven 2002Voice Source Characterization8 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

Emasters School Leuven 2002Voice Source Characterization9 Fundamental frequency (Hz) Vocal Intensity (dB SPL) Sample density Voice profile / density

Emasters School Leuven 2002Voice Source Characterization10 Fundamental frequency (Hz) Vocal Intensity (dB SPL) Sample density Voice profile / speech area

Emasters School Leuven 2002Voice Source Characterization11 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 …

Emasters School Leuven 2002Voice Source Characterization12 Crest factor Vocal Intensity (dB SPL) Fundamental frequency (Hz) Crest factor

Emasters School Leuven 2002Voice Source Characterization13

Emasters School Leuven 2002Voice Source Characterization14 Real time presentation Screen presentation One data point per F 0 -I cell Advanced data storage [new] Full audio signal Full distribution of data per F 0 -I cell Data for screen presentation

Emasters School Leuven 2002Voice Source Characterization15 Advantages Reusability of recordings Statistical analysis per F 0 -I cell Study of time-varying behavior

Emasters School Leuven 2002Voice Source Characterization16 Crest factor Vocal Intensity (dB SPL) Fundamental frequency (Hz) Crest factor

Emasters School Leuven 2002Voice Source Characterization17 Median smoothing of crest factor Vocal Intensity (dB SPL) Fundamental frequency (Hz) Crest factor Crest factor median smoothed

Emasters School Leuven 2002Voice Source Characterization18 Vocal Registers Different movement patterns of the vocal folds Pulse register (creaky voice) Modal register Falsetto register

Emasters School Leuven 2002Voice Source Characterization19 Pulse register Less than 50 Hz Irregular Long closed period

Emasters School Leuven 2002Voice Source Characterization20 Fundamental Frequency (Hz) Vocal Intensity (dB SPL) Pulse register

Emasters School Leuven 2002Voice Source Characterization21 Modal register “Normal” use of voice Active role of M. Vocalis Vocal folds thick and completely vibrating Wide range in F 0 and intensity Flat spectrum

Emasters School Leuven 2002Voice Source Characterization22 Fundamental frequency (Hz) Vocal Intensity (dB SPL) Modal register

Emasters School Leuven 2002Voice Source Characterization23 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)

Emasters School Leuven 2002Voice Source Characterization24 Fundamental frequency (Hz) Vocal Intensity (dB SPL) Falsetto register

Emasters School Leuven 2002Voice Source Characterization25 Fundamental frequency (Hz) Vocal Inensity (dB SPL) Register overlap

Emasters School Leuven 2002Voice Source Characterization26 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

Emasters School Leuven 2002Voice Source Characterization27 Fundamental frequency (Hz) Vocal Intensity (dB SPL) Chest voice and Head voice chest head

Emasters School Leuven 2002Voice Source Characterization28 Registers and voice profiles With a description using Iso-crest factor lines Iso-jitter lines

Emasters School Leuven 2002Voice Source Characterization29 Iso-crest factor lines 4 dB 6 dB Vocal Intensity (dB SPL) Crest factor Fundamental frequency (Hz)

Emasters School Leuven 2002Voice Source Characterization30 Vocal Intensity (dB SPL) Fundamental frequency (Hz) 3 % Jitter (%) Iso-jitter lines

Emasters School Leuven 2002Voice Source Characterization31 New representation Areas defined by iso-parameter lines –crest factor < 4 dB –crest factor > 4 dB, < 6 dB –crest factor > 6 dB –jitter < 3 % –[relative rise time < 6 %]

Emasters School Leuven 2002Voice Source Characterization32 Areas in the phonetogram Vocal Intensity (dB SPL) Fundamental frequency (Hz) Jitter > 3%, unstable RRT < 6 % pressed-like Crest factor < 4 dB sine-like

Emasters School Leuven 2002Voice Source Characterization33 Fundamental frequency (Hz) Vocal registers in the phonetogram Falsetto upper boundary Modal lower boundary Chest voice boundary Vocal Intensity (dB SPL)

Emasters School Leuven 2002Voice Source Characterization34 Comparison of voice profiles Characterisation of Voice pathologies Voice classifications Reuse stored voice profiles of subjects with known voice history

Emasters School Leuven 2002Voice Source Characterization35 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

Emasters School Leuven 2002Voice Source Characterization36 Unit for comparison Voice profile unit defined by small range of F 0 and Vocal Intensity Distributions of acoustic voice parameters per unit Probability density function per parameter Model Hidden Markov Model We need

Emasters School Leuven 2002Voice Source Characterization37 two unconnected states per phonetogram unit vocal registers start and end of phonetion Unit model

Emasters School Leuven 2002Voice Source Characterization38 SpeechVoice Profile phoneme modelF 0 /I unit model not labeledlabeled by F 0 and I spectral envelopeacoustic voice parameters language modelunrestricted transitions “forced alignment recognition” Correspondences

Emasters School Leuven 2002Voice Source Characterization39 Crest factor distributions

Emasters School Leuven 2002Voice Source Characterization40 Fundamental frequency (Hz) Vocal Intensity (dB SPL) Distinctiveness Most distinctive states

Emasters School Leuven 2002Voice Source Characterization41 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