[Usefulness of electroglottogram (EGG) and photoglottogram (PGG) for the analysis or vocal fold vibration--a high speed digital imaging study].

Simultaneous recordings of EGG, PGG and high-speed digital imaging (HSDI) of vocal fold vibration were made in 3 normal male subjects and the results were compared to evaluate the usefulness of EGG and PGG for the analysis of the vibratory pattern. Each subject was required to produce sounds of 3 different pitches at 3 different intensity levels in the recording sessions and the 27 sets of data samples were collected. For each data set, the glottal area waveform (GAW), glottal width waveform (GWW), EGG, differentiated EGG, PGG, differentiated PGG, and voice waveform were displayed in a graphic form on the same time axis and their patterns were compared. Based on the analysis of GAW and GWW, it was found that there were variations in the pattern of closing and opening of the vocal fold margin corresponding to the differences in the type of phonation. The EGG waveform appeared to correspond well to that of the movement of the vocal fold margin in the closing phase, while the correspondency was less apparent in the opening phase. It is considered that the EGG waveform is dependent on the mode of contact between the two vocal folds and that a careful observation of the EGG is useful and practical for predicting the pattern of vocal fold vibration. On the other hand, it was difficult to determine the onset of the closing and opening phases only from PGG waveform and there was a timing difference between the PGG and GAW. Although PGG seemed to be useful for judging the presence or absence of the opening phase and for the pitch measurement, it is considered to be unsuitable for a precise cycle-by-cycle analysis of the pattern of vocal fold vibration.