RESUMO
The present work considers systems whose dynamics are governed by the nonlinear interactions among groups of 6 nonlinear waves, such as those described by the unforced quintic nonlinear Schrödinger equation. Specific parameter regimes in which ensemble-averaged dynamics of such systems with finite size are accurately described by a wave kinetic equation, as used in wave turbulence theory, are theoretically predicted. In addition, the underlying reasons that the wave kinetic equation may be a poor predictor of wave dynamics outside these regimes are also discussed. These theoretical predictions are directly verified by comparing ensemble averages of solutions to the dynamical equation with corresponding solutions of the wave kinetic equation.
RESUMO
The purpose of this study was to investigate possible differences in acoustic characteristics of phonation between populations of European and African origin. The subjects were 33 adult males divided in two groups. Group One consisted of 17 men of African origin, and Group Two included 16 men of European origin. All subjects were without vocal pathology at the time of the investigation, smokers and non-smokers. Sustained phonation of the vowel /a/ was acoustically analyzed by the Real-time Frequency Analyzer (Bruel and Kjaer, type 2123). Variables included f0, intensity of f0, intensity of harmonics 1-7, jitter and noise level intensity. One-way variance analysis showed statistically significant difference between the two groups in intensity of the second harmonic only. The same analysis has been repeated with non-smokers and showed statistically significant differences in intensities of the second and the third harmonic leading to assumption that there may be fine differences in vocal fold vibration between Group One and Group Two. Factor congruence analysis showed differences between samples in factor structures. It could be possible that these differences reflect psychoacoustic level.
