Subglottic pressure is the pressure that builds up beneath (“Sub-“) the vocal folds (“glottis”). The amount of subglottic pressure generated is determined by the airflow through the leakage of air between the vocal folds and the resistance to that flow. The resistance is determined by the  stiffness, tensioning and mass.

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http://www.speech.kth.se/prod/publications/files/qpsr/1990/1990_31_4_059-079.pdf