Objectives: In previous work, we showed that a rigid larynx-like geometry can generate a sound by itself. However, very little is known about the exact mechanisms and control of the larynx during the first cry of life. The goal of this work was to understand how the very first cry is generated.
Methods: Simultaneous high-speed imaging and sound recording on 2 excised 38-week term human fetus larynges were performed. The behaviors of the vocal folds and the false vocal folds were studied separately. The behavior of the vocal folds after resection of the supraglottic structures was also analyzed. A comparative acoustic analysis of the first cry and of the sound generated by the excised organs was performed.
Results: Our data showed that the vocal folds in a larynx with the pressure conditions of the first cry do not generate sound themselves, but induce aerodynamic conditions leading to vibrations of other parts of the larynx.
Conclusions: The similarities between the sound generated by an excised larynx and the first cry suggest a lack of neurologic control of the larynx during production of the first cry. A model-algorithm is proposed.