ISSN:0001-4966    

DOI:10.1121/1.1919068

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The increase in acoustic power output of a constant‐strength point monopole caused by boundaries can be found directly from the value of the imaginary part of the reflected pressure at the source. Waterhouse obtained an expression for the power output of a source by assuming that the plane could be specified by a pressure‐reflection coefficient (R) that is Independent of the angle of incidence. It is shown here that for some geometries the power output is independent of the angular dependence ofR. When the source is located over an infinite plane, the increase in acoustic power output can also be found by using admittance boundary conditions. Some solutions are presented for this configuration and are compared with the results obtained by Waterhouse.

ISSN:0001-4966    

DOI:10.1121/1.1919072

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1919074

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

In computing the mean‐square generalized force (or the joint acceptance) of a structure undergoing excitation by random pressures, approximations can often be made that will greatly reduce the computational effort and that do not affect the accuracy significantly. It is shown that the mean‐square generalized force has an upper bound that is easy to compute, useful for irregular‐mode shapes or correlation functions. In addition, it is shown that spatial variations in the mean‐square pressure of an antisymmetric nature over the surface do not affect the joint acceptance, while the effect of symmetrical variations is small.

ISSN:0001-4966    

DOI:10.1121/1.1919078

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

An exact expression for the discrimination factor (ratio of maximum‐to‐minimum power response) has been found for a vertical, equally spaced, linear steered array in an axially symmetric, peaked noise field. This quantity was evaluated for half‐wavelength element spacing as a function of the number of elements, and for a 20‐element linear array as a function of the interelement spacing. These calculations refine a previous approximate result obtained by Stone [J. Stone, J. Acoust. Soc. Am.34, 328 (1962)].

ISSN:0001-4966    

DOI:10.1121/1.1919080

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

An analysis of signals received on a bottomed hydrophone from a series of explosive charges, dropped across the North Atlantic Ocean and described in a previous paper, indicates attenuation coefficients about 50% greater than those for transmission along the deep sound‐channel axis. The attenuation is attributed to forward scattering by inhomogeneities in the body of the sea.

ISSN:0001-4966    

DOI:10.1121/1.1919082

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

A theoretical analysis of the space time correlations of random noise measured at two points separated a distance ξ and heighthabove a reflecting plane is formulated. The random‐incidence correlation function is discussed for noise independent of angle of incidence, omnidirectional receivers, and for a reflection coefficient Γ = ±1. Certain aspects of the resulting anisotropy of the noise field are pointed out, but attention is directed toward predicting the influence of the receiving‐point‐aspect ratio 2h/ξ on the value of the measured correlation function. It is shown that the space‐time correlation function for large‐aspect ratios approaches in the limit a form identical with that resulting for zero reflection Γ = 0. Also, the possibility of reducing the value of the spatial‐correlation function for band‐limited noise by judicious choices of ξ and 2h/ξ is pointed out.

ISSN:0001-4966    

DOI:10.1121/1.1919085

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP