Typing vocal fold vibratory patterns in excised larynx experiments via digital kymography.

OBJECTIVES: Signal typing is central to the understanding of vocal fold vibratory patterns. Digital kymography (DKG) allows the direct observation of vocal fold vibratory patterns, and therefore, using DKG for vibratory signal typing may provide a useful complement to traditional signal typing techniques.

METHODS: Video data collected from 20 larynges excised from mongrel dogs were observed with DKG in order to find examples of type 1 (nearly periodic), type 2 (subharmonic), and type 3 (aperiodic) vibratory patterns. The time series, frequency spectra, and correlation dimensions were calculated for each signal type.

RESULTS: The type 1 pattern showed a periodic time series of glottal edges and a discrete frequency spectrum. The type 2 vibratory pattern displayed a time series of alternating high- and low-amplitude waves and a frequency spectrum that included a subharmonic (F0/2) frequency component. Regular and symmetric vibratory patterns were observed in the type 1 and type 2 patterns. The type 3 vibratory pattern was characterized by an aperiodic time series of glottal edges, a broadband frequency spectrum, and irregular and asymmetric vibratory patterns. The correlation dimension estimates increased from type 1 to type 2 to type 3.

CONCLUSIONS: Imaging with DKG demonstrated an ability to assign a signal type to various laryngeal vibrations. Signal typing techniques utilizing direct observation of the vocal folds could be useful in determining valid methods for the analysis of vocal fold vibrations.