摘要:

The velocity of propagation and attenuation of longitudinal waves has been determined for a six‐ring polyphenyl ether, bis[m‐(m‐phenoxy phenoxy) phenyl] ether. The viscosity, density, and shear relaxation properties of this liquid are known from previous measurements. It is found that the relaxing partK2of the compressional modulus is equal to43times the limiting value of the shear modulusG∝, but the volume viscosity ηris approximately4 × 43times the shear viscosity η. Within experimental error, the shape of the reduced relaxation curves for the components of the complex compressional modulus is the same as that found for the corresponding components of the complex shear modulus. This indicates that the shear and compressional relaxation processes have a common origin. These findings are compared with previously published results for associated liquids.

ISSN:0001-4966    

DOI:10.1121/1.1911732

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Measurements were made on the effect of pressure on ultrasonic absorption in a 0.5Maqueous solution of manganese sulfate at 25°C. A cylindrical resonant cavity was used for obtaining absorption in the frequency regions of 300 and 500 kHz, at pressures up to 20 000 psi. Results are similar to those obtained forMgSO4, in that absorption decreases by a factor of about 3 for a pressure increase of 15 000 psi. Independent conductivity data show nearly the same behavior forMnSO4as forMgSO4solutions, namely, an increase of only about 14% in the concentration of dissociated ions for the same pressure increase. These results forMnSO4appear to be inconsistent with the model used by Atkinson and Kor to analyze their data. The large effect of pressure on ultrasonic absorption is similar to that observed by Carnevale for 0.1MMnSO4at 60°C from 9 to 75 MHz.

ISSN:0001-4966    

DOI:10.1121/1.1911733

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

A theoretical and experimental investigation of the molecular absorption process in air has been carried out with particular reference to the variation of Napier frequency (fmax) with water‐vapor concentration (h′). It turns out that the relationship between these two quantities is a quadratic only at very low humidities and that, over the rest of the humidity range, the general relationship derived here is best approximated by an equation of the formfmax = const h′x, where 1

ISSN:0001-4966    

DOI:10.1121/1.1911734

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

This paper presents measurements of the acoustic emission from gas bubbles of controlled sizes “seeded” into water and glycerol‐water mixtures and subjected to sound fields over a wide range of frequencies and intensities up to, and beyond, the transient cavitation threshold. The emission from unprepared liquids was also recorded for comparison. A mechanical device has been developed for generating small bubbles of uniform sizes at controlled rates. The results suggest that there are at least two mechanisms for generating signals below the excitation frequency (f0): (1) Subharmonics off0may be produced by forced oscillations of bubbles whose radial resonance frequencies are submultiples off0; (2) bubbles of any size may be shock excited to emit signals at their radial resonance frequencies. Large bubbles of certain preferred sizes are normally present, and their resonances probably account for many low‐frequency signals that are not integral submultiples off0. It also seems certain that some other mechanism unconnected with resonant bubbles contributes to the relatively strong signals observed at the first subharmonic (f0/2).

ISSN:0001-4966    

DOI:10.1121/1.1911735

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The vibrational relaxation of nitrogen is proposed for the mechanism of the anomalously large absorption of sound found at low frequency and high relative humidity in air.

ISSN:0001-4966    

DOI:10.1121/1.1911736

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The linearized equations for the flow of a compressible inviscid fluid in an accelerated sphere were solved for a constant step in the acceleration from a state of rest. Pressure waves whose maximum amplitude is nearly equal to the hydrostatic pressure from an equivalent steady gravitational field acting through the depth of the diameter are induced in the fluid. This maximum pressure occurs at the end of that diameter aligned in the direction of the acceleration. By means of the convolution integral, the pressure distribution on the inner surface of a sphere being accelerated sinusoidally was obtained and the reaction force resulting from the fluid motion was computed. The pressure oscillations build up in a resonant manner with amplitude linear with time when the driving‐reduced frequency is equal to an eigenvalue of the problem.

ISSN:0001-4966    

DOI:10.1121/1.1911737

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The propagation of a sinusoidal wave of small amplitude in an initially isotropic viscoelastic solid, which is subjected to a static pure homogeneous deformation, is discussed. The secular equation for a plane wave propagating an arbitrary direction with respect to the principal directions of the static deformation is derived. The complex slownesses corresponding to propagation along the principal axes of the static strain are found. Relations are obtained between these and the principal stresses associated with the static deformation, which generalize earlier formulas obtained by Ericksen for elastic materials.

ISSN:0001-4966    

DOI:10.1121/1.1911738

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The theory of wave scattering from a rough surface has been used to calculate reflection from a rough layer. Mathematical expressions have been developed for the average value and the variance of the scattered power. These expressions take into account multiple reflections in the layer between the top and the bottom interfaces. The variance of the scattered power is expressed as a series. The terms of this series decrease rapidly.

ISSN:0001-4966    

DOI:10.1121/1.1911739

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Arbitrary‐body acoustic radiation is simulated by an inside source distribution whose field satisfies the boundary vibration. Together with the expansion of Kirchoff's integrand in the ratio of source points and observation point locations, a proposed perturbation process is shown to converge for ratios that are less than unity. Within the frame of perturbation, the class of vibration (good vibration) was shown to bypass the eigenvalue difficulties by analytical inversion. The results are consistent with spherical pulsation, spherical oscillation, and Morse's solution for spherical‐cap vibration. Application of the method to transient analysis is also indicated.

ISSN:0001-4966    

DOI:10.1121/1.1911740

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

A theoretical study is presented on the propagation of a plane sinusoidal wave through a material that is reinforced with parallel fibers in one direction. The wave propagates in a direction normal to the fibers, and both fiber and matrix are made of linear elastic materials. An integral formulation for the scattered‐wave solution of an isolated fiber is used to study the multiple scattering in an infinite slab of the composite material. The transmitted and reflected waves from the composite and from a homogeneous slab are shown to be similar. By matching the two sets of results, formulas expressed in terms of the isolated‐fiber solution are derived for the wave speed, the effective density, and the modulus of the composite. In general, the effective density and modulus so defined are complex numbers and depend on the wave frequency. This fact indicates the possible existence of dissipation and dispersion in the composite under dynamic loadings. A series solution is presented for a composite containing circular fibers, and approximate closed form results are obtained for the limiting case of very long wavelength. As expected, the material does not exhibit dispersion and dissipation at this limit.

ISSN:0001-4966    

DOI:10.1121/1.1911741

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP