摘要:

Noise surveys have been made in a number of recently developed suburban communities, as well as in well‐established communities that are not penetrated by major expressways or railroads. Measurements of background‐noise levels are presented and compared with earlier published data. The findings indicate a change in midfrequency‐band levels that should be considered in developing zoning and nuisance‐control statutes.

ISSN:0001-4966    

DOI:10.1121/1.1918971

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The diffraction loss‐distance characteristics in crystals have been computed for the single‐slit transducer geometry in ultrasonic pulse‐echo measurements. The characteristics are functions of elastic anisotropy and show several local maxima and minima before becoming monotonic at large distances from the transducer. By applying scale factors to the ordinates and abscissas of the characteristics, they were made applicable to the case of a circular transducer. The scale factors were chosen to bring the computed single‐slit characteristic for isotropic materials into coincidence with the well‐known isotropic‐diffraction characteristic for circular‐piston sources. The scaled crystal characteristics served to predict the positions of the local loss maxima to 15% and their amplitudes to 25% or better in four experiments. Certain crystals produce less diffraction loss per unit length than others because of the dependence of diffraction on anisotropy. The scaled diffraction loss‐distance characteristics can be used for computing diffraction corrections for ultrasonic attenuation.

ISSN:0001-4966    

DOI:10.1121/1.1918972

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

A proof is presented that the energy‐transfer ratios of the various elastic‐wave modes reflected and transmitted at a plane boundary between two media are symmetrical and equal to the product of the forward‐ and backward‐reflection coefficients. This relationship is shown to hold for several types of lossless boundary conditions at a solid‐solid interface.

ISSN:0001-4966    

DOI:10.1121/1.1918973

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The generation and reception of ultrasonic waves are discussed with the aim to improve existing wedge‐type angle probes used for nondestructive testing. A number of wedge materials are discussed, and it is shown that constructions using separate transducers for the generation of shear waves and reception of compressional waves in the wedge yield a higher echo‐transmission factor, larger signal‐to‐noise ratio, and a larger monitor signal than constructions using one transducer only.

ISSN:0001-4966    

DOI:10.1121/1.1918974

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The reflection of electromagnetic waves normally incident on the surface of a liquid supporting a spherical sound wave is discussed theoretically. The effect of Bragg reflection is neglected, and only the microscopic movement of the liquid surface is taken into account. Because of the periodic nature of the sound wave, the reflected electromagnetic signal contains frequency components that correspond to both the sum and the difference of the electromagnetic and acoustic frequencies. These two frequency components have quite different properties. The problem is treated by perturbation theory, and two special cases are examined in detail.

ISSN:0001-4966    

DOI:10.1121/1.1918975

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

A method is developed whereby the natural frequencies of a nonuniform beam may be determined in a relatively straightforward manner. The novelty of the present approach stems from the fact that dynamic programming techniques are employed to eliminate the need for an initial guess as to modeshape (Rayleigh‐Ritz) or frequency (Myklestad). The basic scheme herein developed may be applied with minor modification to a wide class of elasticity problems that can be formulated in terms of minimization of an energy integral.

ISSN:0001-4966    

DOI:10.1121/1.1918976

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The anomalies in the audiofrequency compliances reported by Fitzgerald [J. Acoust. Soc. Am.32, 1270 (1960)] were searched for in vain. In particular, the measured shear compliances were independent of frequency and prestress within the experimental error of about 4% over a range of these variables within which Fitzgerald reported a variation of one to two orders of magnitude. The present technique involves a vibrating duplex reed; the biasing steady stress is of either piezoelectric or thermal origin. An extension of the common theory of the “bimetallic strip” to anisotropic materials is presented.

ISSN:0001-4966    

DOI:10.1121/1.1918977

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The technique of forced vibration has been applied to the study of the properties of viscoelastic materials. It is found, through the analysis of a free sphere with a harmonic oscillating internal source, that the vibration‐amplitude ratio of two measuring points is associated with the complex dilational constants and a complex ratio directly related to the complex Poisson's ratio of the material. From the criterion of maximum amplitude ratio (i.e., by adjustment of the frequency of the source for the amplitude ratio to reach a maximum), these properties can be expressed in terms of the amplitude ratios and their frequencies. For the convenience of laboratory testing, two particular amplitude ratios, in conjunction with their frequencies, have been considered for this purpose. Simple expressions are given, relating the properties of the test material to quantities measurable in the laboratory: namely, the maximum amplitude ratios and their corresponding frequencies.

ISSN:0001-4966    

DOI:10.1121/1.1918978

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Free vibrations of nonuniform cantilever beams with an end mass have been investigated, using the equations of Bernoulli‐Euler. Two configurations of interest are treated: (a) constant width and linearly variable thickness; and (b) constant thickness and linearly variable width. Charts have been plotted for each case from which the fundamental frequency, the second harmonic, and the third harmonic can be easily determined for various taper ratios and ratios of end mass to beam mass. The Tables from which these charts were plotted are also included.

ISSN:0001-4966    

DOI:10.1121/1.1918979

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Equations for the determination of the frequencies of flexural vibration and corresponding modal shapes for cylindrically aeolotropic circular plates are presented. A considerable analysis has been made of the case of symmetric vibrations, and results are tabulated. The theory is exemplified by an analysis of the vibration of a circular plate with circular stiffeners for which the effective elastic compliances had been determined in a previous investigation. Nodal patterns and corresponding frequencies were experimentally determined for the first five symmetric modes and the first four asymmetric modes of a simply supported stiffened plate. Comparison between the theoretical and experimental results for the first three symmetric modes is provided. Finally, some discussion given for the important problem of approximating plates with attached stiffeners by equivalent homogeneous uniformly thick aeolotropic plates.

ISSN:0001-4966    

DOI:10.1121/1.1918980

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP