Open slope quotient: a new glottographic parameter.

This study introduces a new objective measurement of the vibratory pattern termed the open slope quotient (OSQ). This parameter is based on the maximum slope of the photoglottographic waveform during glottal opening. Using an excised canine larynx model, the electroglottographic and photoglottographic waveforms, sound intensity, and subglottic pressure were recorded as vocal fold tension; glottic width and airflow rate were systematically varied. Multiple regression analysis of the data from nine larynges revealed OSQ to be inversely related to glottic width (p < 0.001) and vocal fold tension (p < 0.001) and directly related to glottic resistance (p < 0.001) and subglottic pressure (p < 0.001). The OSQ was better correlated with glottic width, subglottic pressure, and glottic resistance than speed quotient. OSQ is related to the velocity of vocal fold opening and laryngeal resistance. OSQ may also be related to vocal fold stiffness.