摘要:

The scattering of time‐harmonic spherical acoustic waves by a penetrable sphere with statistically irregular surface has been studied. The first and the second moments of the potential fields are computed. The asymptotic expressions of the moments of the fields for a small corrugated sphere are also derived. For the purpose of illustration, a simple example, a small corrugated sphere of radius,a, with its mean surface defined by〈r̃〉 = a(1 + ε sinθ + ε cosθ sinφ), is considered and the far field scattering amplitude of its second moment is calculated and plotted.

ISSN:0001-4966    

DOI:10.1121/1.1910552

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

The acoustic nonlinearity of an orifice in a plate has been investigated by measuring simultaneously the oscillatory flow velocity in the orifice and the acoustic‐pressure fluctuations producing the flow. The relation between the pressure and velocity amplitudes, which is linear at sufficiently low pressures, is found to approach a square‐law relation at large velocity amplitudes. By evaluating the phase relationship between the fundamental harmonic components of pressure and velocity, the acoustic‐orifice impedance is determined. In the square‐law region of the pressure/velocity relation, the resistive component of the orifice impedance dominates and is proportional to the velocity amplitude. This method of measurement, which is particularly useful at high amplitudes, is supplemented by measurements of sound transmission and frequency response of the orifice plate so that an impedance curve can be constructed over an extended range of amplitudes. An analogous program of measurements has been carried out to study the influence of a superimposed steady flow on the acoustic‐orifice impedance. Finally, as an application of the results obtained, the absorption characteristics of resonator absorbers for high‐intensity sound are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1910576

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

The problem of the scattering of elastic waves by a random set of inhomogeneities is extended to high frequencies. As in the case of scattering of scalar waves at high frequencies, the mean‐square scattered amplitudes for elastic waves vary as the square of the frequency. The scattering processP‐S, important at low frequencies, is vanishingly small at high frequencies; the ratio of the amplitudes of the scattering processesS‐StoP‐P, although still large, is significantly reduced as one proceeds from low frequencies to high.

ISSN:0001-4966    

DOI:10.1121/1.1910549

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

This paper deals with the calculation of eigenvalues of acoustical waveguides with arbitrary cross section. The method presented herein makes use of conformal mapping techniques and Galerkin's method to solve the transformed wave equation. Numerical calculations are presented for two types of boundary conditions: (a) zero velocity, and (b) zero pressure at the walls.

ISSN:0001-4966    

DOI:10.1121/1.1910556

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

The far‐field acoustic pressure generated by an infinite plate driven by a point and a line force are computed. This paper constitutes an extension of previous computations [G. Maidanik and E. M. Kerwin, Jr., J. Acoust. Soc. Am.40, 1034–1038 (1966)]. The extension is in the sense that the plate considered here is backed by a third medium that is terminated by a parallel infinite baffle. It is shown that when the absolute value of the acoustic reflection coefficient of the baffle approaches unity, the presence of the baffle may substantially affect the far‐field acoustic pressure. The far‐field acoustic pressure when the spaces in the front and the back of the plate are occupied by different fluid media is briefly considered.

ISSN:0001-4966    

DOI:10.1121/1.1910568

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

The far‐field acoustic pressure generated by an infinite plate driven by a point and a line force are computed. This paper constitutes an extension of previous computations [G. Maidanik, J. Acoust. Soc. Am42, 27–31 (1967)]. The plate considered in this paper is covered uniformly and completely by a compliant coating which is applied in turn to the front and back of the plate. The formalism accounts for different fluids' occupying the space in front of the plate and in the cavity back of the plate.

ISSN:0001-4966    

DOI:10.1121/1.1910569

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

The radial propagation of axial shear waves in nonhomogeneous elastic media is solved by both the Laplace transform technique and the method of characteristics. Closed‐form solutions for certain cases of non‐homogeneity are obtained by the former technique. Numerical integration of the characteristic equations yields results that are in good agreement with those obtained by Laplace transforms. For certain problems, the method of characteristics yields solutions unattainable by Laplace transforms.

ISSN:0001-4966    

DOI:10.1121/1.1910570

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

Free‐vibration experiments were conducted on two‐ and three‐dimensional models of a centrosymmetric cubic crystal. Frequencies and mode shapes were determined. Also, some theoretical calculations were made of the frequencies and mode shapes, using previously measured elastic constants. Several classes of vibrations were identified.

ISSN:0001-4966    

DOI:10.1121/1.1910571

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

An approximate analysis of the response in the fundamental mode of any simple single‐span beam with tuned viscoelastic dampers attached at discrete locations is presented. A harmonic loading with arbitrary spatial distribution is assumed. It is shown that, to a good degree of approximation, a single expression can be made to represent the response in the fundamental mode of a beam with any boundary conditions, provided that certain effective mass and stiffness parameters are defined for the beam/damper configuration. Comparisons are made with an exact theory, subject to the limitations of the Euler‐Bernoulli beam equation, of the response and damping of a cantilever beam having an isolated tuned viscoelastic damper and an isolated harmonically varying load at the free end. Good agreement between the exact and approximate theories is demonstrated. Conclusions are drawn concerning the equivalent damping introduced into the simple structure by the tuned dampers and the damper natural frequency needed for optimal damping.

ISSN:0001-4966    

DOI:10.1121/1.1910572

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

A method is developed for analyzing vibratory systems that may exhibit yielding or other hysteretic behavior under broad‐band random forcing. The techniques rely on a balance of power supplied by the forcing and dissipated in hysteretic effects. Since the application area involves the practical case of lightly damped structures, a transformation into normal‐mode coordinates is used even for systems exhibiting nonlinear damping. One‐ and two‐degree of‐freedom examples are considered in detail and general concepts are given where possible. Limitations inherent in the method are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1910573

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP