Development of a glottal area index that integrates glottal gap size and open quotient.

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 extracted from high-speed videoendoscopy 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 principal component derived from tokens without glottal gaps was significantly (p < 0.01) associated with the open quotient (OQ). The alternating-current (AC) measure had a significant effect (p < 0.01) on the first principal component among tokens exhibiting glottal gaps. A measure AC/OQ, defined as the ratio of AC to OQ, was proposed to combine both amplitude and temporal characteristics of the glottal area waveform for both complete and incomplete glottal closures. Analyses of "glide" phonations in which quality varied continuously from breathy to pressed showed that the AC/OQ measure was able to characterize the corresponding continuum of glottal area waveform variation, regardless of the presence or absence of glottal gaps.

Variability in the relationships among voice quality, harmonic amplitudes, open quotient, and glottal area waveform shape in sustained phonation.

Increases in open quotient are widely assumed to cause changes in the amplitude of the first harmonic relative to the second (H1*-H2*), which in turn correspond to increases in perceived vocal breathiness. Empirical support for these assumptions is rather limited, and reported relationships among these three descriptive levels have been variable. This study examined the empirical relationship among H1*-H2*, the glottal open quotient (OQ), and glottal area waveform skewness, measured synchronously from audio recordings and high-speed video images of the larynges of six phonetically knowledgeable, vocally healthy speakers who varied fundamental frequency and voice qualities quasi-orthogonally. Across speakers and voice qualities, OQ, the asymmetry coefficient, and fundamental frequency accounted for an average of 74% of the variance in H1*-H2*. However, analyses of individual speakers showed large differences in the strategies used to produce the same intended voice qualities. Thus, H1*-H2* can be predicted with good overall accuracy, but its relationship to phonatory characteristics appears to be speaker dependent.

Age, sex, and vowel dependencies of acoustic measures related to the voice source.

The effects of age, sex, and vocal tract configuration on the glottal excitation signal in speech are only partially understood, yet understanding these effects is important for both recognition and synthesis of speech as well as for medical purposes. In this paper, three acoustic measures related to the voice source are analyzed for five vowels from 3145 CVC utterances spoken by 335 talkers (8-39 years old) from the CID database [Miller et al., Proceedings of ICASSP, 1996, Vol. 2, pp. 849-852]. The measures are: the fundamental frequency (F0), the difference between the "corrected" (denoted by an asterisk) first two spectral harmonic magnitudes, H1* - H2* (related to the open quotient), and the difference between the "corrected" magnitudes of the first spectral harmonic and that of the third formant peak, H1* - A3* (related to source spectral tilt). The correction refers to compensating for the influence of formant frequencies on spectral magnitude estimation. Experimental results show that the three acoustic measures are dependent to varying degrees on age and vowel. Age dependencies are more prominent for male talkers, while vowel dependencies are more prominent for female talkers suggesting a greater vocal tract-source interaction. All talkers show a dependency of F0 on sex and on F3, and of H1* - A3* on vowel type. For low-pitched talkers (F0 < or = 175 Hz), H1* - H2* is positively correlated with F0 while for high-pitched talkers, H1* - H2* is dependent on F1 or vowel height. For high-pitched talkers there were no significant sex dependencies of H1* - H2* and H1* - A3*. The statistical significance of these results is shown.