摘要:

The theory of scattering of plane waves of sound is extended to scatterers in the form of thin elastic shells of cylindrical and spherical shape. As for all elastic scatterers, the scattering action is the resultant of (1) “rigid body scattering,” i.e., the scattering which would be present if the scatterer were rigid and immovable; (2) “radiation scattering,” which represents the sound radiation from the shell undergoing forced vibrations under the influence of the incident wave pressure and which is determined by the dynamic characteristics of the submerged shell. Contrarily to solid scatterers whose dynamic characteristics are little differentin vacuoand in the fluid medium, the characteristics of shells are profoundly altered by fluid reaction. When the shell is excited near resonance, the scattering pattern resembles the dynamic response of the shell in that it is highly frequency sensitive.

ISSN:0001-4966    

DOI:10.1121/1.1917522

出版商:Acoustical Society of America    

年代:1952

数据来源: AIP

摘要:

Consider a moving surface, on which the time derivatives of velocity and pressure are discontinuous but on which the velocity and pressure themselves are continuous. Such discontinuities may correspond to dissipated shock waves or “weak shocks.” Then under the assumption that each moving fluid element undergoes adiabatic changes, it can be shown that the surface is given by the solution of a generalized eikonal equation, which in the case of a fluid at rest becomes the ordinary eikonal equation of ray acoustics. This treatment does not require the usual assumption of infinitesimal amplitudes ordinarily used in acoustics. Conservation laws corresponding to those in ray theory are also derived under the above assumptions.

ISSN:0001-4966    

DOI:10.1121/1.1917528

出版商:Acoustical Society of America    

年代:1952

数据来源: AIP

摘要:

With the advent of barium titanate as a piezoelectric material, the construction of transducers whose active elements can be in a wide variety of shapes became possible. The theoretical sensitivity of an interesting structure consisting of a transversely loaded, centrally supported, circular, barium titanate bimorph is calculated using the results of elasticity theory. Some experimental verification is presented.

ISSN:0001-4966    

DOI:10.1121/1.1917531

出版商:Acoustical Society of America    

年代:1952

数据来源: AIP

摘要:

The ultrasonic properties of dry,CO2‐free air have been measured at 32°C andf/pvalues ranging from 2 to 125 Mc/atmos. Dispersion of the velocity has been found beginning at 30 Mc/atmos, accompanied by a large increase in absorption such that measurements could not be made above 130 Mc/atmos with the equipment used. Changes in velocity, absorption, and specific heat are interpreted as owing to the slowing of energy exchange between translational and rotational states. The relaxation time derived from the dispersion measurements has been found to be 2.29 × 10−9sec, corresponding to a midpoint of the dispersion curve at 116 Mc/atmos.

ISSN:0001-4966    

DOI:10.1121/1.1917536

出版商:Acoustical Society of America    

年代:1952

数据来源: AIP