Biomechanical modeling and bifurcation theory are applied to study phonation onset and register transition. A four-mass body-cover model with a smooth geometry is introduced to reproduce characteristic features of chest and falsetto registers. Sub- and supraglottal resonances are modeled using a wave-reflection model. Simulations for increasing and decreasing subglottal pressure reveal that the phonation onset exhibits amplitude jumps and hysteresis referring to a subcritical Hopf bifurcation. The onset pressure is reduced due to vocal tract resonances. Hysteresis is observed also for the voice breaks at the chest-falsetto transition. Varying the length of the subglottal resonator has only minor effects on this register transition. Contrarily, supraglottal resonances have a strong effect on the pitch, at which the chest-falsetto transition is found. Experiment of glissando singing shows that the supraglottis has indeed an influence on the register transition.

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The proposed MR-stethoscope presents a promising alternative to currently available techniques for cardiac gating of (ultra)high field MRI. Its intrinsic insensitivity to interference from electromagnetic fields renders it suitable for clinical imaging because of its excellent trigger reliability, even at 7.0 Tesla.

Magnetic Resonance Imaging (MRI)o fm oving organs requires synchronization with physiological motion or flow, which dictate the viable windowfor data acquisition. To meet this challenge, this study proposes an acoustic gating device (ACG)t hat employs acquisition and processing of acoustic signals for synchronization while providing MRI compatibility,immunity to interferences with electro-magnetic and acoustic fields and suitability for MRI at high magnetic field strengths. The applicability and robustness of the acoustic gating approach is examined in apilot study,where it substitutes conventional ECG-gating for cardiovascular MR. The merits and limitations of the ACGa pproach are discussed. Implications for MR imaging in the presence of physiological motion are considered including synchronization with other structure-or motion borne sounds.

Objective: To give new insights into the pathogenesis of vocal fold nodules: (a) why the female/male ratio is so extreme, (b) how an hourglass-shaped vibration pattern – eliciting a localized microtrauma – originates, and (c) what the roles of muscular tension imbalance and of behavioral aspects are. Materials and Methods: Simulations with a 3-dimensional computer model of the vibrating vocal folds. Results and Conclusion: (1) A slightly incomplete dorsal vocal fold adduction is a first condition for inducing an hourglass vibration pattern. (2) A limited collision zone is only possible with a small degree of curving of the rest position of the vocal fold edges in their ventral portion. This is an anatomical characteristic of the adult female larynx. Muscular fatigue and resulting hypotonia seem to enhance this curving. (3) If both these conditions are fulfilled, a sufficient vibration amplitude is required to achieve a localized impact. (4) This third condition can be obtained by an increased subglottal pressure and/or by a decrease in active stress of the tension forces between the neighboring vocalis masses. These last aspects incorporate muscular tension imbalance (dyskinesia) and behavioral aspects in the modelling process. Decrease in active stress is a possible effect of fatigue, and increase in subglottal pressure a result of effort compensation.