摘要:

Diffraction lobes can be eliminated from the ultrasonic wave pattern emitted by an ultrasonic transducer by producing a Gaussian distribution of amplitudes across the transducer surface. A simple way to accomplish this is described.

ISSN:0001-4966    

DOI:10.1121/1.1912546

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The scattering of time‐harmonic spherical scalar waves by a large, convex, and lossy object with a statistically corrugated surface is considered. The maximum deviation of the corrugated surface from the smooth one is assumed to be small, and hence the boundary‐perturbation technique is used in this study. First, the scattering of scalar waves by a large lossy sphere with statistical surface irregularities is treated as a canonical problem in the general discussion. After the effective reflection coefficient is derived for the sphere case, the asymptotic expressions of mean values of the scattered wave function and the scattered intensity are obtained for the general problem.

ISSN:0001-4966    

DOI:10.1121/1.1912547

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The measured velocity dispersion of an isotropic square aluminium bar shows close agreement with that predicted by the modified theory of Nigro, except for one “displaced” harmonic which lies off the smooth graph, and another harmonic that is split into two resonances (a doublet). The displaced harmonic can be attributed to the proximity of an “end resonance,” and the doublet occurs at the frequency where the first complex mode becomes real for the equivalent cylinder.

ISSN:0001-4966    

DOI:10.1121/1.1912548

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The extensional vibrations of a thin cylindrical shell as described by Love and Haskins and Walsh [J. Acoust. Soc. Amer.29, 729–734 (1957)] are discussed, using concepts recently presented by Drumheller and Kalnins [J. Acoust. Soc. Amer.47, 1343–1353 (1970)]. Additional numerical results are presented and used to discuss the coupling of the longitudinal and radial motions. Calculations are presented to illustrate the “in phase” and “out of phase” modes described by Drumheller and Kalnins.

ISSN:0001-4966    

DOI:10.1121/1.1912549

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The formulation of a general solution to the forced motion of a linear viscoelastic body having a constant Poisson's ratio with a time‐dependent body force, a time‐dependent traction on part of the boundary, a time‐dependent displacement on the remainder of the boundary, and nonzero initial conditions is given.

ISSN:0001-4966    

DOI:10.1121/1.1912550

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The frequency equation is derived for a uniform chain fixed at the upper end and carrying a concentrated mass at the free end. The first five natural frequencies are determined for a wide range of end mass to chain mass ratios. It is shown that for mass ratios exceeding eight, simplified relations may be used to approximate the natural frequencies.

ISSN:0001-4966    

DOI:10.1121/1.1912551

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The spatial and temporal correlation function of the sea surface, quantities required in underwater acoustic studies, can be formulated via the surface‐wave energy spectrum. For two spectral functions, proposed by Neumann‐Pierson and by Pierson‐Moskowitz for a fully developed sea, time and space correlation functions are calculated numerically. The latter ones, although functions of two variables, can be constructed from two auxiliary functions, dependent only on correlation distance, when a cosine‐squared law for the directionality of the wave spectrum is assumed. These auxiliary functions are tabulated and plotted. The two spectra produce results that differ only slightly.

ISSN:0001-4966    

DOI:10.1121/1.1912552

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The approach presented by the author of the subject paper is not new, having appeared in numerous papers in recent years. Further, in his application of the method to an ocean with linear sound‐speed profile, few novel results are presented since this problem has been investigated previously.

ISSN:0001-4966    

DOI:10.1121/1.1912553

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The approach to the multiple‐surface‐reflection problem in a linear‐gradient medium presented by D. T. Raphael [J. Acoust. Soc. Amer.47, 1437–1439 (1970)] is a new approach and different from the one developed by M. J. Jacobson [J. Acoust. Soc. Amer.36, 2298–2305 (1964)]; the former exploits an acquiring‐ray angle solution for a linear‐gradient medium in order to solve the problem, whereas the latter involves Snell's law substitutions and can be used to accomplish the same.

ISSN:0001-4966    

DOI:10.1121/1.1912554

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The approach presented in the subject paper is new in that it treats cases where the ray parameter is expressed as an explicit function of range and receiver depth. This approach exhibits the mathematical nature of caustic lines in a clear and simple form as contrasted to approaches where the ray parameter is expressed as an implicit function.

ISSN:0001-4966    

DOI:10.1121/1.1912555

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP