Peter Assmann

Professor - Behavioral and Brain Sciences
Tags: Cognition and Neuroscience

Professional Preparation

Ph.D. - Speech Production and Perception
University of Alberta - 1985
M.Sc. - Speech Production and Perception
University of Alberta - 1979
B.A. - Psychology
University of Waterloo - 1976

Research Areas

Research Interests

My research investigates the perceptual strategies used by listeners to recognize speech. Speech communication has an extraordinary resistance to distortion: intelligibility is preserved when a substantial portion of the spectrum is eliminated by filtering, when large segments of the waveform are deleted or replaced by silence, or when the signal is embedded in background noise. Research in my lab has centered on a series of experimental investigations of the distortions introduced by competing voices, narrow bandpass filtering, spectral flattening, local time reversal, and frequency scaling. We are evaluating theoretical and computational models of speech perception to account for the extraordinary resilience of human speech communication to such distortions. Our studies of frequency-scaled speech have revealed the operation of perceptual mechanisms that help listeners cope with the enormous variability in the acoustic patterns of speech across talkers. Much of this variability is a direct consequence of size differences in the larynx and vocal tract as a function of age and sex.

Supported by a grant from the National Science Foundation, we are studying the detailed pattern of these changes in a database of speech recordings from adults and children ranging in age from 5 to 18 years. These recordings provide materials for constructing stimuli in listening experiments, acoustic parameters for realistic voice synthesis and voice conversion, and normative data for studies of speech perception and production in adults and children. This project is providing valuable information on the nature of speech development and the acoustic scaling transformations that take place as children grow into adults. Acoustic measurements from the recorded samples are incorporated into statistical pattern recognition models to predict the responses of listeners to natural and synthesized speech. These models provide a basis for testing and refining hypotheses about the perceptual transformations that listeners apply to cope with acoustic variability, and the processes by which they extract phonetic and indexical information in speech perception.

Speech perception research at The University of Texas at Dallas

Listeners can extract information from speech produced under extreme conditions: for example, when the speaking rate is 400 words per minute; in high levels of background noise; and when the identity of the speaker is unknown. Current research in our laboratory considers how human listeners achieve this by looking at auditory, perceptual, and cognitive processes that intervene between the production of speech and its recognition. We are developing and testing models of the auditory and phonetic analysis of speech to describe how listeners extract information from speech when competing sound sources are present. When the competing sound source is another voice, listeners face the difficult problem of separating signals that are similar in their acoustic structure. This problem has serious implications for theoretical models of speech perception, and it has important practical consequences for two areas of applied speech research. First, because competing voices present difficulties for individuals suffering from sensorineural hearing impairments, research on the perceptual processes involved in speech-source segregation may provide insights into the problems faced by these listeners, and may suggest forms of signal processing to enhance the intelligibility of speech signals corrupted by background noise. Second, because competing voices severely degrade the performance of automatic speech recognizers, it is likely that a better understanding of human performance will lead to improvements in the design of robust and noise-resistant devices for automatic speech recognition.

Publications

Bharadwaj S.V., Tobey E.A., Assmann P.F. and Katz W.F. (2006). Effects of Auditory Feedback on Fricative Consonants Produced by Cochlear Implant Users: Acoustic and Perceptual Evidence. Journal of the Acoustical Society of America 119: 1626-1635. 2006 - Publication
Stickney G.S., Loizou P.C., Mishra L.N., Assmann P.F., Shannon R.V., Opie J.M. (2006). Effects of electrode design and configuration on channel interactions. Hearing Research 211(1-2): 33-45. 2006 - Publication
Assmann P.F., Dembling S., and Nearey T.M. (2006). Effects of frequency shifts on perceived naturalness and gender information in speech. Proceedings of the Ninth International Conference on Spoken Language Processing, pp. 889-892, Pittsburgh, PA, September 17-21, 2006. 2006 - Publication
Assmann, P.F. and Katz, W.F. (2005). Synthesis fidelity and vowel identification. Journal of the Acoustical Society of America 117(2), 886-895. 2005 - Publication
Glidden, C.M. and Assmann, P.F. (2004). Effects of visual gender and frequency shifts on vowel category judgments. Acoustics Research Letters Online 5(4), 132-138. 2004 - Publication
Stickney, G.S., Zeng, F.G., Litovsky, R., Assmann, P.F. (2004). Cochlear implant speech recognition with speech maskers. Journal of the Acoustical Society of America. 116(2), 1081-1091. 2004 - Publication
Loizou, P.C., Stickney, G., Mishra, L, and Assmann, P.F. (2003). Comparison of Speech Processing Strategies Used in the Clarion Implant Processor. Ear and Hearing 24(1): 12-19. 2003 - Publication
Assmann, P.F. and Nearey, T.M., (2003). Frequency shifts and vowel identification. Proceedings of the 15th International Congress of Phonetic Sciences, pp. 1397-1400, Barcelona, Spain. 2003 - Publication
Assmann, P.F. and Nearey, T.M., (2003). Frequency shifts and vowel identification. Proceedings of the 15th International Congress of Phonetic Sciences, Barcelona, Spain, 3-9 Aug 2003.. 2003 - Publication
Assmann, P.F. and Nearey, T.M. (2003). A review of results on frequency shifts and vowel identification. Canadian Acoustics 31. 2003 - Publication

Appointments

Research Scientist
The University of Texas at Dallas [2018–Present]
Associate Professor
University of Alberta [1995–Present]
Assistant Professor
University of Alberta [1989–1995]
Speech and Hearing Scientist
University of Waterloo [1985–1988]

Additional Information

PROFESSIONAL HONORS AND AWARDS
  • Associate Editor for Speech Perception. Journal of the Acoustical Society of America (2002-present), Callier Excellence Scholar. 2001-2002.
  • Special Faculty Research Assignment. Multimedia program for speech perception. Spring, 2002.
  • National Institutes of Health Reviewer, SBIR Special Emphasis Panel, Biobehavioral and Social Sciences IRG, Washington, Nov. 4, 1998.
AD HOC REVIEWER
  • Journal of the Acoustical Society of America
  • Journal of Phonetics
  • Journal of Speech, Hearing and Language Research
  • Journal of Experimental Psychology: Human Perception and Performance
  • IEEE Transactions on Speech and Audio Processing
  • Quarterly Journal of Experimental Psychology
  • Perception and Psychophysics
  • Language and Speech
  • Phonetica
  • Ear and Hearing
  • Music Perception
  • Hearing Research
  • Emotion and Motivation
  • National Science Foundation Research Grants
  • Social Sciences and Humanities Research Council of Canada Research Grants
  • U.K. Science and Engineering Research Council (SERC) Research Grant
PROFESSIONAL SOCIETIES
  • Association for Research in Otolaryngology
  • Acoustical Society of America
  • International Phonetic Association
  • International Speech Communication Association (ISCA)

Funding

Perception of frequency-shifted speech
$223,418 - National Science Foundation Grant [2008–2007]
Perceptual adaptations to frequency-shifted speech
$1,500 - Human Development Faculty Research Initiative [2002–2003]
Modeling the perception of speech under adverse listening conditions
$12,500 - Callier Excellence in Education Grant [2001–2002]
A pattern recognition approach to phonetic and phonological effects in speech perception
- Social Sciences and Humanities Research Council of Canada [2000–2003]
Perception of time-varying spectral cues in speech
$1,500 - Human Development Faculty Research Initiative [2000–2001]