The effect of subglottal acoustics on vocal fold vibration

Acoustic pressures above and below the vocal folds produce a push-pull action on the vocal folds which can either help or hinder vocal fold vibration. The key variable is acoustic reactance, the energy-storage part of the complex acoustic impedance. For the subglottal airway, inertive (positive) reactance does not help vocal fold vibration, but helps to skew the glottal airflow waveform for high frequency harmonic excitation. Compliant (negative) reactance, on the contrary, helps vocal fold vibration but does not skew the waveform. Thus, the benefit of subglottal reactance is mixed. For supraglottal reactance, the benefit is additive. Inertive supraglottal reactance helps vocal fold vibration and skews the waveform, whereas compliant supraglottal reactance does neither. The effects will be demonstrated with source-filter interactive simulation.