On parameterizing glottal area waveforms from high-speed images

Abstract

Because voice signals result from vocal fold vibration, perceptually-meaningful vibratory measures should quantify those aspects of vibration that correspond to differences in voice quality. In this study, glottal area waveforms were calculated from high-speed images of the vocal folds. Principal component analysis was applied to these waveforms to investigate the factors that vary with voice quality. Results showed that the first two principal components were significantly (p < 0.01) associated with the open quotient and the ratio of alternating-current to direct-current components. However, these conventional source measures, which are based on glottal flow, do not fully characterize observed variations in glottal area pulse shape across different glottal configurations, especially with respect to patterns of glottal closure that may be perceptually important. A source measure, the Source Dynamic Index (SDI), is proposed to characterize glottal area waveform variation for both complete and incomplete glottal closures. Analyses of “glide” phonations in which quality varied continuously from breathy to pressed showed that the SDI is able to characterize the corresponding continuum of glottal area waveform variation, regardless of the presence or absence of glottal gaps. [Work supported in part by NSF and NIH.]