Volume 107, Issue 2, February 2000
Index of content:
- ULTRASONICS, QUANTUM ACOUSTICS, AND PHYSICAL EFFECTS OF SOUND 
Ultrasonic absorption in critical binary mixture of perfluoromethylcyclohexane and carbon tetrachloride107(2000); http://dx.doi.org/10.1121/1.428260View Description Hide Description
The results of ultrasonic absorption and velocity measurements for the system perfluoromethylcyclohexane-carbon tetrachloride are presented. In addition, viscosity measurements were made. Ultrasonic absorption at 5, 7, 10, 15, 21, and 25 MHz, above critical temperature is analyzed using the dynamic scaling theory of Ferrell and Bhattacharjee. The values of vs show a good agreement with the theory. The experimental values of for the binary mixture are compared to the scaling function
Comparison between the dispersion curves calculated in complex frequency and the minima of the reflection coefficients for an embedded layer107(2000); http://dx.doi.org/10.1121/1.428262View Description Hide Description
Analytical solutions of Lamb functions for symmetric and antisymmetric elastodynamic modes propagating within a solid layer embedded in an infinite medium are presented. Alternative theoretical analyses of such modes are performed, first in terms of the usual approach of harmonic heterogeneous plane waves (real frequency and complex slowness) and then in terms of transient homogeneous plane waves (complex frequency and real slowness). An example structure of a 0.1-mm-thick “alpha case” (an oxygen-rich phase of titanium that is relatively stiff) plate embedded in titanium is used for the study. A large difference between the usual dispersion curves calculated in real frequency and complex slowness and those calculated in complex frequency and real slowness is shown. Thus the choice between a spatial and a temporal parameter to describe the imaginary part of the guided waves is shown to be significant. The minima and the zeros of the longitudinal and shear plane-wave reflection coefficients are calculated and are compared with the dispersion curves. It is found that they do not match with the dispersion curves for complex slowness, but they do agree quite well with the dispersion curves for complex frequency. This implies that the complex frequency approach is better suited for the comparison of the modal properties with near-field reflection measurements.
107(2000); http://dx.doi.org/10.1121/1.428263View Description Hide Description
Traditional broadband transmission method for measuring acoustic dispersion requires the measurements of the sound speed in water, the thickness of the specimen, and the phase spectra of two transmitted ultrasound pulses. When the sound speed in the specimen is significantly different from that in water, the overall uncertainty of the dispersion measurement is generally dominated by the uncertainty of the thickness measurement. In this paper, a new water immersion method for measuring dispersion is proposed which eliminates the need for thickness measurement and the associated uncertainty. In addition to recording the two transmitted pulses, the new method requires recording two reflected pulses, one from the front surface and one from the back surface of the specimen. The phase velocity as well as the thickness of the specimen can be determined from the phase spectra of the four pulses. Theoretical analysis and experimental results from three specimens demonstrate the advantages of this new method.
107(2000); http://dx.doi.org/10.1121/1.428264View Description Hide Description
ResonantUltrasound Spectroscopy (RUS) of a spherical sample in a pressurizing gas atmosphere was investigated experimentally and theoretically. Measurements were made on a fused silica sphere in He, Ar, and gases up to pressures of 120 bar. The pressure-dependent shift in the resonant frequency, and the Q-factor were measured for the S00, S11, and T02 modes. A theoretical model based on acoustic radiation impedance was used to calculate and the radiation-resistance component, of the Q-factor. Agreement between theory and experiment was good for but there were discrepancies for It was found that the theoretical due to gas-loading effects associated with acoustic radiation was very small and consistent with the observed dependence on pressure and gas species for the T02 mode but not for the S00 and S11 modes. We conclude that the T02 mode is the most reliable of these modes to use in measuring third-order elastic constants by RUS.
107(2000); http://dx.doi.org/10.1121/1.428261View Description Hide Description
The recent experimental results of J. Holzfuss, M. Rüggeberg, and R. Mettin [Phys. Rev. Lett. 81, 1961 (1998)] in which a second harmonic drive system was used to generatesonoluminescence (SL) have been analyzed in the context of the dissociation hypothesis (DH) of D. Lohse and S. Hilgenfeldt [J. Chem. Phys. 107, 6986 (1997)]. The second harmonic introduces two more variables that are under experimental control: a phase and an additional pressure term to the acoustic drive pressure. Diffusive equilibrium curves for a fixed gas concentration were calculated as was the Mach criterion. A phase space diagram was constructed to permit the prediction of regions of stable SL, unstable SL, stable non-SL, and unstable non-SL. These were compared to Holzfuss' experimental observations, and excellent quantitative agreement was seen. The results provide further evidence that the underlying assumptions of DH are sound. They also indicate the utility of DH for determining appropriate experimental conditions to achieve SL and for optimizing an experimental system.