Three dimensionality of the intraglottal flow

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Voice production is governed by the fluid-structure interaction (FSI) that occurs between the airflow coming from the lungs and the vocal folds, which results in the self-sustained oscillation of the glottis. This vibratory motion is characterized by opening, closing, and closed phases, and the majority of sound is produced during the mid to latter closing. Studies have shown that a faster reduction of glottal flow rate (due to increased closing speed or increased deceleration of the airflow velocity), also known as the maximum flow declination rate (MFDR), determines the acoustic intensity and the amount of energy in the higher harmonics. Higher harmonics are important for intelligibility in noise but not in quiet, a major symptom for patients with voice disorders. The glottis is convergent during opening and divergent during closing. These alternating shapes result in an increase in intraglottal pressure during opening and a decrease (and possibly negative) during closing, which facilitate vibrations. Our long-term goal is to ultimately develop a method that enables detailed intraglottal volumetric flow measurement in a vibrating tissue model of the larynx. This project will advance the method we have developed for measuring intraglottal flow distribution in a single plane toward measuring the intraglottal volume flow distribution in a static physical model of the larynx. The proposed work is based on recent advancements we have made using tomographic particle image velocimetry (tomo-PIV) to capture the dynamics of the volume flow distribution above the glottal exit11. Toward this goal, our specific aim is: 1) Develop a method for measuring intraglottal volume flow distribution. Under this aim, we will first demonstrate the intraglottal flow measurement technique in a static physical model of the larynx. The model's dimensions will be similar to an excised canine larynx and its static geometry will capture the main features of divergent glottis. We expect to see differences in the intraglottal vortices and other glottal jet features between the anterior, posterior, and the mid-membranous aspects of the glottis. We will then validate the intraglottal volume flow measurement technique with auxiliary flow measurements techniques. We expect to show that the intraglottal flow characteristics (e.g., mean velocity, turbulence levels and vortical strength) will match the different measurement techniques within 10%.