Self-entrainment of the right and left vocal fold oscillators

Abstract

This article presents an analysis of entrained oscillations of the right and left vocal folds in the presence of asymmetries. A simple one-mass model is proposed for each vocal fold. A stiffness asymmetry and open glottis oscillations are considered first, and regions of oscillation are determined by a stability analysis and an averaging technique. The results show that the subglottal threshold pressure for 1:1 entrainment increases with the asymmetry. Within that region, both folds oscillate with the same amplitude and with the lax fold delayed in time with regard to the tense fold. At large asymmetries, a region involving several different phase entrainments or toroidal regimes at constant threshold pressure appears. The effect of vocal fold collisions and asymmetry in the damping coefficients of the oscillators are explored next by means of numerical analyses. It is shown that the damping asymmetry expands the 1:1 entrainment region at low subglottal pressures across the whole asymmetry range. In the expanded region, the oscillator with the lowest natural frequency is dominant and the other oscillator has a large phase advance and small amplitude. The theoretical results are finally compared with data collected from a mechanical replica of the vocal folds.

Difference between the vocalizations of two sister species of pigeons explained in dynamical terms

“…A systematic analysis of the solutions of our dynamics system indicates that departing from Q=1, it is more difficult for the LTMs to stay locked. The smaller the value of Q, the larger β has to be for the LTMs to stay locked (Lucero et al 2015). Fig.…”

“…Ishizaka and Flanagan (1972) were the first to model this internal structure of the oscillating element in terms of two coupled masses. Many versions of this conceptual model have been proposed in the literature, but they all share a search of equilibrium between mathematical simplicity and a sensible description of the diversity of physical phenomena shaping the force on the oscillating tissue (Lucero and Koening 2005; Lucero et al 2015). The phase difference of the distances between LTMs at the top and at the bottom is ultimately responsible for the existence of a high pressure when the LTMs display a convergent profile, and a low pressure when the profile is divergent.…”

“…In region II (grey area), the membranes display nontrivial dynamics and sounds presents sidebands around the fundamental frequency. (Adapted from Lucero et al 2015)…”

Speech-Based Parameter Estimation of an Asymmetric Vocal Fold Oscillation Model and its Application in Discriminating Vocal Fold Pathologies

“…Each of these have proven to be useful in different contexts. For the purpose of this study, the 1-mass body-cover model [6,18,19,20] is of particular interest. It assumes that a glottal flow-induced mucosal wave travels upwards within the transglottal region, causing a small displacement of the mucosal tissue which attenuates down within a few millimeters into the tissue as an energy exchange happens between the airstream and the tissue [6].…”

Experimental study on level difference between left and right vocal folds

“…Steinecke and Herzel [2] simplified the asymmetric two-mass model to study bifurcations underlying the voice instability. Lucero et al [3] derived analytical formula for the phonation onset of the asymmetric vocal fold model. Phase difference between the left and right vocal folds [4,5], subharmonics [6], biphonations [7], and irregular chaotic oscillations [8] have been reported.…”