Time-domain parameterization of the closing phase of glottal airflow waveform from voices over a large intensity range

The aim of this paper is to analyze and compare two time–domain parameterization methods of the glottal flow waveform on a large intensity range. The first parameter is the classical closing quotient which indicates the portion of a period where the glottis is closing. The second parameter is the recently developed normalized amplitude quotient which is defined using the ratio between the maximum flow amplitude and the negative peak amplitude of the differentiated glottal flow. The parameters are shown to be strongly correlated, and the normalized amplitude quotient to be a more accurate, consistent and robust measure than the closing quotient. The subjects, five female and six male, produced sustained phonations on a large intensity range. On this material, the normalized amplitude quotient is shown to vary systematically with sound pressure level, and it reveals information that for the closing quotient is hidden in local variance.