摘要:

An experimental study has been carried out to determine the natural frequencies of vibration of solid, isotropic, elastic cylinders with free boundaries. Solid aluminum and steel cylinders having height‐to‐radius ratios (h/a) between 0.2 and 3.3 have been studied. Twenty of the graver modes were excited by means of a barium titanate driver loosely coupled to the metal cylinders. Six modes of circumferential order zero, seven modes of order unity, four modes of order two, and three modes of order three were studied in the range of dimensionless frequency parameter ωa/cfrom zero to 2.6. Sand patterns and a small vibration probe were used to determine the form of the vibrations. Where possible, the frequencies are compared with the results of existing theory.

ISSN:0001-4966    

DOI:10.1121/1.1918918

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

This paper presents the development and solution of the differential equations of motion of a system of n elastically connected parallel beams. Using the results developed for the generaln‐beam system, the particular case of a two‐beam system was analyzed in detail. The frequencies and associated mode shapes for various support conditions are presented explicitly. Vibration experiments were performed to ascertain the degree of applicability of the theory. It was found that at least up to the eighth mode reasonably good agreement obtains.

ISSN:0001-4966    

DOI:10.1121/1.1918919

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

A system of approximate, two‐dimensional equations is derived for the thermoelastic response of crystal plates. The equations take into account the coupling of thickness‐shear, flexural, and extensional motion with symmetric and antisymmetric thermal modes. The thermoelastic dissipation predicted at high frequencies by the approximate theory is compared with a three‐dimensional solution, using the free vibrations of an AT‐cut quartz plate as a basis of comparison.

ISSN:0001-4966    

DOI:10.1121/1.1918920

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

A generalized Hamilton's principle and the associated variational equation of motion are presented for finite elastic deformations. By means of the generalized variational equation of motion, it is possible to deduce immediately the usual nonlinear equations of elasticity, such as were discussed by Novozhilov. The inconsistence Novozhilov's work for a simplified nonlinear case of technical importance is pointed out. In its linearized version, the generalized variational equation of motion is next employed in the derivation of plate equations for both flexural and extensional motions, which are finally compared with those given by previous authors.

ISSN:0001-4966    

DOI:10.1121/1.1918921

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

This paper discusses the problems arising in the realization of practical, wide‐band signal correlation systems and presents some possible solutions to these difficulties. Function generators and shift‐register encoders in particular solve the problem of long, stable delays, by providing wide‐band signals that can be reproduced accurately with any desired time delay or Doppler compensation. The use of clipped signals permits operation over a wide range of input‐signal amplitudes, while sacrificing absolute amplitude information and some processing gain. High search rates and processing real time are achieved with multichannel correlators, compressed‐time correlators, and matched filters. Several ways of instrumenting digital delay‐line time compressors, digital‐scanned‐storage time compressors, and digital matched filters are discussed, including their integration into real‐time processing systems. The relative advantages of the different approaches are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1918922

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Geometric spreading of sound in a medium with any given continuous velocity profile is investigated theoretically. The sound velocity is assumed to be dependent on one space coordinate only. The analysis is based on Snell's law. Time and initial angle of the ray are the two independent variables. A set of differential equations describing spreading loss is developed. These equations are solved analytically for the case of constant‐velocity gradient yielding well‐known results. A short discussion of both analog‐ and digital‐computer solutions for the general case is given. Discontinuous velocity profiles and the interchange of sound source and receiver are also considered.

ISSN:0001-4966    

DOI:10.1121/1.1918923

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The longitudinal space‐time correlation function of the fluctuating pressures at the wall in turbulent airflow has been investigated, using the U.S. Navy Underwater Sound Laboratory's 3.5‐in. turbulent‐pipe‐flow facility. Data were obtained for various Reynolds numbers and transducer separations, and were analyzed by using filters of constant 30‐cps bandwidth. These measurements of the longitudinal space‐time correlation function are compared with a mathematical model that takes into account the effect of finite filter bandwidths.

ISSN:0001-4966    

DOI:10.1121/1.1918924

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Expressions are derived for the sound pressure and mutual‐radiation impedance for rectangular pistons on an infinitely long rigid cylinder, and numerical results are presented for typical cases. A comparison of mutual‐radiation impedance for pistons on cylinders, spheres, and planes is made.

ISSN:0001-4966    

DOI:10.1121/1.1918925

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Acoustic bottom‐reflection coefficients have been measured at five ocean, lake, and river locations. A correlation technique was employed, using octave‐band random noise from 200 to 3200 cps as a source. Values obtained ranged from −0.92 to +0.55. Only at Lake Travis, Texas, did the coefficient change substantially with frequency. Angle of incidence made little or no difference up to 45°. Further evidence is presented that pressure‐release bottoms are fairly common.

ISSN:0001-4966    

DOI:10.1121/1.1918926

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Data obtained from the measurement of backscattering of sound from the ocean bottom at 16 locations around the coast of the United States of America are presented. Data are given as a function of grazing angle and frequency for mud, sand, and gravel. The range of frequency was 12.5 to 290 kc/sec and the range of grazing angle was 1.0° to 90°. Backscattering increased with grazing angle according to the sin and sin2, depending on the value of angle and the type of sediment. Backscattering increased with frequency according to the 1.6 power for some locations. It is concluded that a knowledge of the particle structure of the bottom is useful in estimating the reverberation level.

ISSN:0001-4966    

DOI:10.1121/1.1918927

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP