An impedance-based inverse filtering scheme with glottal coupling

Source-filter interactions in voice production arise from considering finite glottal impedances that are comparable with that of the vocal tract and/or the subglottal system. Besides the changes in the source behavior, finite glottal impedances also allow for acoustic coupling between the subglottal and supraglottal tracts. Vowel dependence on the subglottal acoustic pressure is evident in recordings of skin acceleration overlying the suprasternal notch. To obtain estimates of other physiologic signals from skin acceleration, an impedance-based inverse filtering scheme that considers acoustic coupling is proposed. The scheme is based on an electrical analog model of a dipole source and assembles multiple approaches to estimate the system impedances. An experimental platform considers simultaneous measurements of skin acceleration, flexible high-speed videoendoscopy, oral volume velocity, intraoral pressure, electroglottography, and radiated acoustic pressure. Recordings of sustained vowels, co-articulated gestures, and pitch glides provide a comprehensive data set to study tract coupling and source-filter interactions. Preliminary results provide insights into the interrelation among the measured signals and illustrate the tissue instabilities of the vocal folds during some of the gestures. Further evaluation in cases of vocal fold pathology is also planned, where source-filter interactions are expected to be even more pronounced.