Second International Workshop on Models and Analysis of Vocal Emissions for Biomedical Applications (MAVEBA 2001)

Florence, Italy
September 13-15, 2001

Stimulated Production of Vowel-Like LX-Waveforms and Spectral Damping in the Absence of Phonation

Christopher J. Moore (1), Susan Jones (2)

(1) North Western Medical Physics, Christie Hospital, Manchester, UK
(2) Department of Speech & Language Therapy, South Manchester University Hospitals, Manchester, UK

Impedance ‘LX' waveforms measured across the neck at the thyroid level during phonation are known to be correlated with vocal fold movement. Changes in vocal fold contact are thought to be the cause of this phenomenon though emerging applications in radiotherapy indicate that both fold and neck tissues are correlated with LX waveform shape. In this paper it is shown that a two-stage tissue damping model with controlled bandpass and passive low pass components is consistent with evidence from gradually degraded, controlled phonation. In particular it is shown that an externally applied stimulus to the vertebral processes of the neck can produce similar impedance waveforms in the absence of phonation and hence no controlled fold contact. It is postulated that this is evidence for radial pressure waves contributing to the classic ‘LX' impedance waveforms and that the primary mechanism for impedance changes may not simply be due to vocal fold contact per se.

Index Terms. Impedance waveforms; Stimulated vowels; Phonation; Radial vibration; Damping, Control function; Normalised spectra

Full Paper

Bibliographic reference.  Moore, Christopher J. / Jones, Susan (2001): "Stimulated production of vowel-like LX-waveforms and spectral damping in the absence of phonation", In MAVEBA-2001, 48-52.