摘要:

An amplitude‐modulated single‐sideband waveform can be separated into two parts, viz., an amplitude or “envelope” term, and a frequency‐modulation term. Some existing proposals for the use of the frequency‐modulation part in speech compression schemes have been investigated, and although these schemes were found to be fallacious, some results having possible application to speech formant tracking were obtained.

ISSN:0001-4966    

DOI:10.1121/1.1908896

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

A thin rectangular liquid jet impinges on the apex of a rigid wedge and, under suitable circumstances, sets itself into any of a number of modes or “stages” of steady‐state transverse oscillation; any mode has associated with it a pattern of vortex production. Excerpts from motion pictures show sequences of jet configurations corresponding to the different modes of oscillation. In a photographic history depicting the buildings of oscillations in an initially quiescent jet, particular interest is attached to the fact that oscillations appearbeforevortices have developed. Observations from these photographs and results from an earlier paper are compared with predictions of recent theories of edge tone production.

ISSN:0001-4966    

DOI:10.1121/1.1908898

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The geometrical or high‐frequency approximation to solutions of the two‐dimensional wave equation in an inhomogeneous medium is considered. A new ordinary differential equation for a quantity which is inversely proportional to the geometrical high‐frequency field intensity (the square of the field amplitude) is derived. This equation, along with the standard ray and phase equations form a system form which a complete wave solution in the high‐frequency asymptotic limit can be calculated numerically, e.g., through the use of a differential analyzer. The examples of a homogeneous medium and a plane stratified inhomogeneous medium are discussed, and the results of the preceding analysis are verified in these two special cases.

ISSN:0001-4966    

DOI:10.1121/1.1908900

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The results of measurement of the acoustic impedance of some viscoelastic fluids in circular tubes are presented. The fluids studied include water, petroleum oil, glycerol, silicone fluid, milling yellow solution, and agar solution, the last three showing elastic effects. One of these elastic effects is the changing of the acoustic reactance from the inertance type to the compliance type. Measured results are presented for frequencies from 3 cps to 300 cps and for tubes having radii in the range 0.0172 cm to 0.354 cm. Methods are presented for determination of the complex coefficient of shear viscosity from the acoustic impedance properties and examples are given.

ISSN:0001-4966    

DOI:10.1121/1.1908902

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

In the calculations concerning the vibrations of thin elastic shells, several approximations called “shell‐theories” have been introduced in an attempt to simplify the mathematical formalism. In this paper one of these approximation methods, known as the Epstein method, is used to obtain the reflected field produced by a plane wave impinging on an infinite plate. The results are given to first order inkh, wherekis the wave number and 2his the thickness of the plate. A comparison with the exact results shows exact agreement to first order.

ISSN:0001-4966    

DOI:10.1121/1.1908904

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Structural fatigue caused by combined sinusoidal and random vibration is of concern in flight proofing of electronic equipment, since such excitation is required by many current ballistic missile equipment specifications. How to predict the fatigue under this vibratory excitation is discussed with particular reference to the relationship of combined vibration to a single sinusoidal substitute.Equations and curves for obtaining the sinusoidal substitute are presented and their application illustrated on a single resonator system.

ISSN:0001-4966    

DOI:10.1121/1.1908906

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The vibration analysis of shallow spherical shells is extended to (a) frequencies of the order of magnitude of the first thickness‐shear mode in an infinite plate and (b) moderately thick shells. A tenth‐order system of three uncoupled differential equations is derived, which govern the nonsymmetric dynamic deformation of a shallow spherical shell subjected to arbitrary time‐dependent surface loads, and separable solutions are obtained in terms of Bessel functions. As an example, a frequency equation is deduced for the determination of natural frequencies higher than those accurately predicted by the classical theory for free vibration of a shallow spherical cap with a clamped edge.

ISSN:0001-4966    

DOI:10.1121/1.1908908

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

A method is presented for computing acceleration, deflection, and velocity response of a damped, single‐degree‐of‐freedom isolator, subject to a random disturbance between finite frequency limits. A closed‐form solution is obtained for the case where the power spectral density is constant within any given bandwidth. The results are plotted in such a manner that the responses to a variable power spectral density function can readily be computed.

ISSN:0001-4966    

DOI:10.1121/1.1908910

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Sound‐speed measurements and corresponding oceanographic data were obtained aboard the bathyscaph TRIESTE to a depth of 5760 m. Subsequent measurements were made in shallow northern waters by lowering the velocimeters and Nansen bottles from a surface ship. Near‐surface measurements agree with the laboratory data of either Del Grosso or Wilson. One set of the deeper measurements aboard the bathyscaph indicates a general agreement with Wilson, but the measured values were less than values computed by Wilson's equations and this difference increased with depth. The acceleration of gravity was measured at a depth of 2286 m and the increase with depth was in rough agreement with the equation in H. V. Sverdrup'sThe Oceans(Prentice‐Hall, Inc., Englewood Cliffs, New Jersey, 1949).

ISSN:0001-4966    

DOI:10.1121/1.1908912

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The problem of propagation of low‐frequency sound in shallow water over several layers and a basement is approached through an image theory in which the first thin layers are lumped together with the water layer. This effective structure is assumed on the basis of expected good transmission through a thin layer (less than one wavelength thick having acoustic properties not very different from those of its bounding media. The required reflection coefficient at the lower boundary of the lumped layer, expressed as a function of range and the order of the image source of a ray, is taken in the form given by Abelés for reflection of plane waves from a layered system. The theory yields calculated transmission loss functions which show reasonable agreement with experimental results. Comparisons of theoretical loss and data obtained at Panama City, Florida, are made over the frequency range 6–244 cps.

ISSN:0001-4966    

DOI:10.1121/1.1908915

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP