Modal Locking Between Vocal Fold Oscillations and Vocal Tract Acoustics

Abstract

During voiced speech, vocal folds interact with the 2 vocal tract acoustics. The resulting glottal source-3 resonator coupling has been observed using mathe-4 matical and physical models as well as in in vivo 5 phonation. We propose a computational time-domain 6 model of the full speech apparatus that contains a 7 feedback mechanism from the vocal tract acoustics 8 to the vocal fold oscillations. It is based on nu-9 merical solution of ordinary and partial differential 10 equations defined on vocal tract geometries that have 11 been obtained by magnetic resonance imaging. The 12 model is used to simulate rising and falling pitch glides 13 of [A, i] in the fundamental frequency (f o) interval 14 [145 Hz, 315 Hz]. The interval contains the first vo-15 cal tract resonance f R1 and the first formant F 1 of [i] 16 as well as the fractions of the first resonance f R1 /5, 17 f R1 /4, and f R1 /3 of [A]. The glide simulations reveal 18 a locking pattern in the f o trajectory approximately

Subglottal pressure oscillations in anechoic and resonant conditions and their influence on excised larynx phonations

“…Titze et al 11 , Wade et al 12 and Zañartu et al 13 reported on occurrences of sudden pitch frequency jumps and other instabilities when the fundamental frequency of oscillation f o was in the vicinity of the first vocal tract resonance frequency. These phenomena were also observed through numerical simulations by several authors 9,[14][15][16][17] . Interactions with subglottal resonances might have a similar influence on the voice source waveform and the vocal fold vibrations as the vocal tract, as observed by Austin et al 18 (using an excised larynx), Zhang et al 19,20 (using vocal fold physical models and an excised larynx), or Lucero et al 21 (using vocal fold physical and mathematical models).…”

Finite-element modeling of vocal fold self-oscillations in interaction with vocal tract: Comparison of incompressible and compressible flow model

“…These differences show interaction between acoustics at compressible solution and other domains and therefore illustrates the importance of the SAI for the behavior of the voice source. Similar effect was published in [46], where changes in CQ and ClQ were caused dominantly by the acoustic loading. 4a and 4b) or the power spectral densities (PSDs, Figs.…”

“…Based on the first groundbreaking models [26,33,57], the recent lumped-mass models are capable of capturing linear or non-linear interactions between the physical domains [75,77], chaotic behavior of the VFs in some regimes [78,79], bulged shape of the VFs [31,47] or sound of the vowel [i:] [33,46].…”

Notes on glottal flow and acoustic inertial effects

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This text is a compilation of some of the notes that the author has written during the development of the low-order model "DICO" [2,8,10,11] for vowel phonation and the even more rudimentary glottal flow model [9] for processing high-speed glottal video data.The following subject matters are covered: (i) Incompressible, laminar, lossless flow models for idealised rectangular and wedge shape vocal fold geometries. Equations of motion and the pressure distribution are computed in a closed form for each model using the unsteady Bernoulli's theorem; (ii) The assumption of incompressibility and energy loss (i.e., irrecoverable pressure drop) of the airflow in airways (including the glottis) is discussed using steady compressible Bernoulli theorem as the main tool; (iii) Inertia of an uniform waveguide is studied in terms of the lowfrequency limit of the the (acoustic) impedance transfer function.

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“…This text is a compilation of some of the notes that the author has written during the development of the low-order model "DICO" [2,8,10,11] for vowel phonation and the even more rudimentary glottal flow model [9] for processing high-speed glottal video data.…”