摘要:

Exact solutions for the interaction between two concentric cylindrical waves and between two concentric spherical waves are presented. The scattered‐pressure amplitude in the far field is shown to be constant in the cylindrical case and to be proportional tor−1lnrin the spherical case, whereris the distance to the source of primary waves.A near‐field solution is derived for the scattered waves generated when two sharply defined, plane‐wave beams of square cross section intersect at right angles. A comparison is made of the theory with recent experiments in which beams of circular cross section were used. It is concluded that if the scattered waves do exist, their amplitudes are at least 40 dB below those that are predicted by this theory.When a hard object is placed in the region of intersection, scattered waves are observed. This effect can be explained by the fact that with the addition of the hard object (a cylinder) the primary waves have components of the same symmetry. These components are the waves scattered from the primary beams by the object. Evidence is presented to show that these components, having the same symmetry, interact strongly in the volume surrounding the object.

ISSN:0001-4966    

DOI:10.1121/1.1918241

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The sound generated by the nonlinear interaction of two sound beams of high intensity, arranged to cross each other perpendicularly, is computed to the first order of interaction. Several of the assumptions and specializations in previous treatments of this problem, whose effects on the result it is hard to estimate, are avoided. The interaction is supposed to take place in the Fraunhofer zone of both beams.Some results obtained are of general validity. For instance, the Doppler angles computed and measured by Ingard and Pridmore‐Brown are found, without any strict specializations of the primary beams and the interaction region.Estimates of the amplitudes of the generated pressure, governing rather wide ranges of frequencies of the primary beams, seem to agree with the previous apparently strongly differing results. This correspondence is brought forward by an amplitude factor, depending on the frequencies of the primary beams.In the high‐frequency limit, the destructive interference among the quadrupoles which give rise to the generated sound dominates the results and gives an over‐all zero value of the generated pressure, in accordance with Westervelt's treatment.

ISSN:0001-4966    

DOI:10.1121/1.1918242

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Experiments are reported on the measurement of the scattered pressure from two finite‐amplitude, collinear sound beams. The measurements were carried out at a carrier frequency of 13.5 Mc in water and of 350 kc in air. The slope of the half‐pressure angle vs difference frequency curve agrees well with that predicted by Westervelt, although the radiation pattern measured experimentally was in each case more directive than predicted by the theory.

ISSN:0001-4966    

DOI:10.1121/1.1918243

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Occasionally, linear dynamical system must operate under the influence of imposed motions of very small amplitude and high frequency which were not contemplated in its design. The influence of such motions on the behavior of the system is therefore of paramount interest. It is shown that, although the differential equations of motion are linear with oscillatory coefficients when the imposed motions are present, it is possible under certain conditions to determine the behavior in an average sense from the solution of a system of linear differential equations with constant coefficients. Criteria to determine the influence of the imposed motions on the stability and response to various inputs of the original system are easily found.

ISSN:0001-4966    

DOI:10.1121/1.1918244

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

A method is presented for determining the differential equations of the output moments of a linear random system in which the coefficients are components of vector Markov processes. The method is based upon well‐known results in applied stochastics. It appears considerably simpler than methods recently suggested for studying the behavior of linear random systems.A stability criterion previously published is obtained with little effort. Reasons are presented for disagreeing with published results that mean motion of linear random systems with Gaussian parameter variations is not influenced by these variations.

ISSN:0001-4966    

DOI:10.1121/1.1918245

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The paper presents a theoretical development of the equations of motion for the flexural vibrations of a shallow spherical shell of orthotropic material. For symmetrical vibrations, the motion is described by two ordinary sixth‐order differential equations with variable coefficients. Factorization of the sixth‐order operators into second‐order operators is discussed and the details of solution are worked out for the case in which the equations are reduced to those for the isotropic shell. It is shown that equations for the latter case agree exactly with those derived previously by Reissner. A table of calculated frequencies is given along with some experimental results for steel shells.

ISSN:0001-4966    

DOI:10.1121/1.1918246

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The solution of the problem of static radial deformation of a piezoelectric spherical shell, polarized in the radial direction corresponding to uniform pressures on the inner and outer surfaces of the shell, and a given voltage difference between these surfaces, coupled with a radial distribution of temperature from the inner to the outer surface, forms the chief interest of the present note. The constitutive relations, deduced by Mindlin are taken in a form which closely resemble those of Toupin.

ISSN:0001-4966    

DOI:10.1121/1.1918247

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Combined random and swept sinusoidal vibration is used in the qualification of missile electronic equipment. The subject of this report is how structural fatigue produced by a combined excitation is related to structural fatigue produced by another combined excitation or to that produced by individually applied random or sinusoidal excitation. In particular, a method is given by which different random or combined random and sinusoidal vibration excitations can be compared. This method finds practical application in comparing vibration specifications and tests, and for the purpose of modifying vibration requirements from one type to another.In this derivation, substitute sinusoidal vibration excitations and sweep rates are based on the response characteristics of a single resonator system, while amplitude and time relationships are based on the S‐N diagram of the material under consideration. Equations and curves are given and their use illustrated by means of a numerical example.

ISSN:0001-4966    

DOI:10.1121/1.1918248

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

General expressions are derived for the loss factors of axially uniform linear composite structures in terms of properties of the constituents. Specializations applicable to practical composites incorporating free and constrained viscoelastic components are introduced. The results are shown to be generalizations of earlier studies of coated and sandwich plates [Ross, Ungar, Kerwin, Sec. 3 ofStructural Damping, ASME (1959)], and it is demonstrated that much of the abundant information available for such plates may be carried over to more complicated structures by redefinition of the structural and shear parameters.

ISSN:0001-4966    

DOI:10.1121/1.1918249

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

A hydrophone assembly with terminals the Lerner Marine Laboratory, Bimini, Bahamas, has been installed on the east bank of the Straits of Florida in order to study the sounds produced by marine animals in the natural environment. Sounds from two bottom‐mounted hydrophones, one in 100 ft of water and the other in 1200 it, were recorded on dual track, magnetic tape on a 24‐h basis. The tapes were played back at eight times recording speed and monitored for sounds possibly of marine animal origin. More than 25 categories of sounds were observed during the initial period from November 1960 to July 1961. A number of the categories showed repetitive, diurnal patterns and possible seasonal patterns of soniferous activity. In general, sound categories the shallow and deep sites were different. Usually, only a single category was heard from a hydrophone at one time. Some tentative identifications have been made.

ISSN:0001-4966    

DOI:10.1121/1.1918250

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP