Wolfgang Hess 60 years young
Speech is beautiful
Louis C.W. Pols
Institute of Phonetic Sciences
University of Amsterdam
Bonn, Sept. 29, 2000
IKP, Bonn
IFA, Amsterdam
Speech is beautiful
most natural form of communication
 it is efficient
 highly complex and challenging
 towards multi- and interdisciplinary communities
 natural speech synthesis  full knowledge
 ASR lasting challenge
 speech is extremely robust to distortions
 speech is eloquent; singing; speeches are awful
 speech community is nice

robustness to degraded speech

partly reversed speech
(Saberi & Perrott, Nature, 4/99)
fixed duration segments time reversed or
shifted in time
perfect sentence intelligibility up to 50 ms
(demo: every 50 ms reversed
original
)
Wolfgang
engineer by training
 emphasis on signal processing (Münich)
 pitch-synchronous spectral analysis
 applied for phoneme and word recognition
 and for voice detection and pitch extraction
 speech synthesis (Bonn)

History, almost 30 yrs ago
7th International Congress on Acoustics 1971,
Budapest, Hungary
 first international (speech) conference
 Satellite Speech Symposium, Szeged
 Hess, “Grundfrequenzsynschrone digitale
Spektralanalyse von Sprachsignalen mit beliebig
feiner Auflösung im Frequenzbereich”

- also papers in German, and even in Russian
- engineering interest in speech analysis
- forthcoming specialization in sp. recogn. & pitch extr.
Budapest ICA
many influential people from international speech
science community, already present there
 topics at that time far away from our present
interests in almost every respect:

- topics and ambitions
- approaches taken
- type and size of data sets

see some names and topics (nostalgia!)
speech processing
Velichko (Russia): dynamic programming
 Bishnu Atal: towards predictive coding
 Sakoe (Japan): dynamic processing for time
normalization
 Osamu Fujimura:
- dynamic palatography,
- electromyography (hooked-wire electrodes),
- computer-controlled dynamic radiography
(Tokio x-ray microbeam generator)
 Jim Flanagan: focal points in sp. comm. research

speech synthesis
Cecile Coker: articulatory synthesis
 Paul Mermelstein & Bishnu Atal: vocal transfer
functions for speech synthesis
 Johan Liljencrants: formant synthesis OVE III
 Helmut Mangold: synthesis with a limited set of
dynamic transitions
 Werner Endress: synthesis via intermediate sounds
 Peter Denes: word concatenation
 Fujimura, Coker & Umeda: prosody in synthesis
 Larry Rabiner: 2-pole digital filters for synthesis
“we were away a year ago”

speech recognition
Hans Tillmann (abs.): Bonner DAWID-II-system
 Kasya, Kido, Krause & Tarnóczy: vowel recogn.
 Velichko: 60 words
 Rao: 225 VCV utterances, diad matching
 Sakoe: 2300 isolated Japanese 10 digits
 Dreyfus-Graf: artificial language
 Erman: 54 isolated words over telephone
 Neeley: 54 words recognition in noise
 Pols: 50 Dutch words, stationary phoneme parts
 Renato de Mori: zero crossings

speech perception, musical
acoustics, psycho-acoustics
Rao: plosive-vowel interaction
 Kozhevnikov: AM vowel-like stimuli
 Ludmilla Chistovich: vowel discrimination
 Johan Sundberg: pitch extraction of folk music
 Max Mathews: music synthesis
 Tammo Houtgast: lateral inhibition in psychoac.
 Evans & Wilson: neurophysiological evidence
 Bela Julesz: critical bands in vision and audition
 Egbert de Boer: reverse-correlation method

Wolfgang’s further carrier
Dissertation in 1972
“Digitale grundfrequenzsynchrone Analyse von
Sprachsignale als Teil eines automatischen
Spracherkennungssystems”
 Masterpiece in 1983, 698-pages book
“Pitch determination of speech signals. Algorithms
and devices”, published by Springer Verlag.
 Chair in Phonetics in Bonn in 1986
 publications, keynotes, conference organizer

ESCA/ISCA and Eurospeech
ESCA grounded in 1988
 Joseph Mariani first president (1988-1993)
 Louis Pols 2nd president (1993-1997)
 Wolfgang final keynote at E’97 in Rhodes
 since Sept. 1997: Roger Moore president
 since death Christian Benoit (April 25, 1998)
Wolfgang secretary of ESCA
 since Eurospeech’99 in Budapest  ISCA

ICA 1971
all speech analysis based on filters or formants
 LPC was about to be introduced
 all synthesis based on formant synthesis
 diphone concept did not yet exist
 virtually no attention for TTS synthesis-by-rule
 all speech recognition based on word-template
matching
 probabilistic approach yet unknown
 vocabulary size of the order of 50 words only

present-day synthesis
mainly corpus-based concatenative synthesis
with non-uniform units (e.g., CHATR,
Festival, Next-Gen, Laureate, Bonner system)
 large storage, optimal search
 high naturalness and intelligibility
 but….one speaker, one style, one application
 room for further improvement

possible improvements
general or application-specific corpus
 how to reduce storage requirements
 annotation details at various levels
 optimize search algorithms and cost functions
 fewer prototypes, generate certain variants
 preferable units, fall-back mechanism
 new voice, speaking style, emotion, rate
 can voice be personalized
(cont.)

possible improvements (cont.)
how much manipulation in concatenation
 combining stored speech and synthetic speech
 better prosody (copy, concept, rules)
 intonation modelling (discrete or continuous;
detailed or sparse; signal oriented or linguistically
meaningful)
 concept for duration modelling
 sentence accent and prominence

presently not very popular
formant synthesis (but see MITalk)
 diphone and demisyllable synthesis (but see
many operational systems: Dutch Fluency,
German Hadifix, Multi-lingual Lucent TTS)
 use of forms of parameterized speech (as soon as
more manipulation is required again)
 many voices, speaking styles, emotions, rates
 importanc of system evaluation (Jenolan Caves)

future for Wolfgang
being in the midst of new and challenging
developments
 to produce
 (in the most efficient way)
 the highest achievable quality of synthetic speech
 (given specific dialogue applications)
 is a large responsibility
 but also a lot of fun to do
(cont.)

future for Wolfgang (cont.)
Wolfgang and the IKP group enjoy doing this
 for German and other languages
 and like to report about it at international
forums
 it attracts many good students
 these are excellent conditions for continuing
this work
 I wish Wolfgang and all his colleague a lot of
success in the years to come!
