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In the present paper, viscously damped free and forced vibrations of circular and annular membranes are investigated using a closed form exact method. Instead of undamped natural frequencies which are typically computed and applied in the free and forced vibration analysis, viscously damped natural frequencies are done. It is certain that the viscous damping affects the natural frequencies. The viscously damped natural frequency equation and the critical viscous damping equation are exactly derived. In the viscously damped free vibration analysis, effects on viscous damping on natural frequencies are studied. In the viscously damped forced vibration analysis, vibratory amplitudes are derived in a closed form exact manner. Accurate displacement amplitude vs. forcing frequency curves showing the forced response due to distributed harmonic loading are displayed. [ABSTRACT FROM AUTHOR]

Summary Study Objective The purpose of this study was to establish preliminary, quantitative data on amplitude of vibration during stroboscopic assessment in healthy speakers with normal voice characteristics. Amplitude of vocal fold vibration is a core physiological parameter used in diagnosing voice disorders, yet quantitative data are lacking to guide the determination of what constitutes normal vibratory amplitude. Methods/Study Design Eleven participants were assessed during sustained vowel production using rigid and flexible endoscopy with stroboscopy. Still images were extracted from digital recordings of a sustained /i/ produced at a comfortable pitch and loudness, with F 0 controlled so that levels were within ±15% of each participant's comfortable mean level as determined from connected speech. Glottal width (GW), true vocal fold (TVF) length, and TVF width were measured from still frames representing the maximum open phase of the vibratory cycle. To control for anatomic and magnification differences across participants, GW was normalized to TVF length. GW as a ratio of TVF width was also computed for comparison with prior studies. Results Mean values and standard deviations were computed for the normalized measures. Paired t tests showed no significant differences between rigid and flexible endoscopy methods. Interrater and intrarater reliability values for raw measurements were found to be high (0.89–0.99). Conclusions These preliminary quantitative data may be helpful in determining normality or abnormality of vocal fold vibration. Results indicate that quantified amplitude of vibration is similar between endoscopic methods, a clinically relevant finding for individuals performing and interpreting stroboscopic assessments. [ABSTRACT FROM AUTHOR]

Vibration has become of increasing interest to health professionals, primarily owing to reports that vibration can increase tissue blood flow. The aim of this review was to investigate the available scientific evidence on the effects of exogenous vibration on skeletal muscle perfusion. The databases searched from inception to December 2010 included Ovid MEDLINE, EMBASE, CINAHL via Ebsco Host and CENTRAL. Experimental and observational studies, where exogenous vibration was an intervention, were included in this review. The main outcomes of interest were muscle blood volume, blood flow, blood flow velocity, arterial diameter and muscle temperature. One reviewer selected studies for inclusion, extracted data and assessed the quality of the eligible studies. Percentage change in muscle perfusion outcome was the measure of treatment effect, and regression analysis was used to investigate associations between vibratory load and muscle perfusion. Twenty-two studies with a total of 302 participants were included in this review. Muscle blood volume increased with vibration in five of nine studies and decreased in two studies; muscle blood flow velocity increased with vibration in five of six studies; muscle blood flow increased with vibration in two of three studies; vibration had a positive effect on arterial diameter in three of three studies; vibration had no effect on muscle temperature in two of two studies. The magnitude of increase in muscle perfusion was positively associated with vibratory load ( P<0·001). We conclude that vibration increases muscle perfusion with the magnitude of increase positively related to the vibratory load applied. [ABSTRACT FROM AUTHOR]

The article presents a research study aimed at analyzing the effect of vocal fold injury on lateral phase difference and vibratory amplitude among dogs. The study is undertaken through repeated measurement of excised canine larynx serving. The results of the study show that medial and anterior injuries lessen the vibratory amplitude among dogs.

Hypothesis: Vocal fold vibration may physically raise intravascular pressure to levels high enough to damage capillaries and result in leakage of erythrocytes. This type of injury is commonly seen in benign vocal fold lesions and is not well explained. Study Design: Theoretical, retrospective. Methods: The relationship of intravascular pressure to vibration frequency and amplitude is derived and confirmed with a physical blood vessel model, then applied to published human measurements to estimate human intravascular pressures. Results: Vocal fold intravascular pressure is predicted to have a quadratic dependence on both frequency and amplitude. During speaking, the pressure may rise to over 20 cmH2O, and may reach levels far higher for screaming and singing. Such pressure magnitudes are known to trigger inflammatory cascades and can lead to fluid leakage. They also have the potential for pharmacologic control with β-agonists. Conclusions: Intravascular pressure likely rises significantly during vocal fold vibration and may lead to the type of injury seen in benign vocal fold lesions. The results support voice therapy aimed at reducing vibratory amplitude. More vibratory amplitude measurements need to be performed in a wider range of subjects before the full range of human vocal fold vascular pressures can be estimated. [ABSTRACT FROM AUTHOR]