摘要:

The equation derived by Kotani and King relating to the excess pressure valid to the second order in the acoustic field is examined. It is shown that the solution of the usual wave equation can be used in the case when the radiation pressure in the Langevin's sense is derived from this equation. The reason as to why not only the normal force but also the tangential force on the nonstiff surface result due to the radiation pressure defined from the viewpoint of the pressure in hydrodynamics, is clarified by considering the motion of the surface. The general expression for the radiation pressure on the rigid object which is in motion due to inertia effect, is led by introducing moving coordinates.

ISSN:0001-4966    

DOI:10.1121/1.1907514

出版商:Acoustical Society of America    

年代:1955

数据来源: AIP

摘要:

A general formula for the radiation pressure acting on a thin rigid circular disk is derived from the theory of the previous paper. Motion of the disk under action of the wave and diffraction of the wave due to the disk are taken into account. Constants which may be calculated by the use of the oblate spheroidal functions necessary in obtaining the radiation pressure are given in the table. Numerical calculation for disks of various weight with the ratio of the circumference of the disk to the wavelength of sound up to 3.5 is carried out.

ISSN:0001-4966    

DOI:10.1121/1.1907515

出版商:Acoustical Society of America    

年代:1955

数据来源: AIP

摘要:

The scattering of a one‐megacycle underwater ultrasonic beam by a radial cylindrical temperature gradient perpendicular to the beam is studied as a function of position and gradient strength. The gradient is produced by a vertical hot wire. The presence of free convection currents makes necessary time average study of both the temperature and scattering distributions. From these studies average temperature and scattering distributions are constructed, and it is found that a possible diffractive transition region exists between temperature gradients of 14.5 and 26.5°C/cm. In addition, there is evidence that a transition from wave to ray acoustics occurs between gradients of 26.5 to 36.5°C/cm.

ISSN:0001-4966    

DOI:10.1121/1.1907516

出版商:Acoustical Society of America    

年代:1955

数据来源: AIP

摘要:

The attenuation of pulsed 10‐megacycle ultrasound in barium titanate ceramics is studied as a function of temperature and applied field. In the region of the coercive field strength attenuation maxima are observed which correlate with a rapid change of the electromechanical response. Both phenomena can be traced to domain wall movements of two different kinds. A model is proposed which identifies one kind of attenuation maximum with a stress equalization in the polarized crystal grains of a ceramic, and the other kind with the nucleation of antiparallel domains. In both cases the losses appear to be caused by an elastic hysteresis due to dislocation movement.

ISSN:0001-4966    

DOI:10.1121/1.1907517

出版商:Acoustical Society of America    

年代:1955

数据来源: AIP

摘要:

It is found that the pattern of piezoelectric voltage on the surface of a resonant crystal corresponds to the pattern of the exciting ultrasonic field. A capacity scanning system is described whereby ultrasonic shadow‐graphs and images are reproduced for observation in a manner similar to that used in television.

ISSN:0001-4966    

DOI:10.1121/1.1907518

出版商:Acoustical Society of America    

年代:1955

数据来源: AIP

摘要:

The problem of obtaining low loss ultrasonic delay lines for switching, computer, and certain radar applications is discussed. An analysis is made of structures using half‐wavelength and quarter‐wavelength bonds between the transducer and the acoustic medium to widen the pass‐band; results are listed for both quartz crystal and barium titanate transducers.For barium titanate transducers (80 percentBaTiO3, 12 percentPbTiO3, 8 percentCaTiO3), it is shown that a theoretical flat band width of approximately 30 percent with less than 1 db midband loss can be obtained with a bond of negligible thickness. This band width can be increased to approximately 46 percent without additional loss if a properly designed bond is used, (i.e.,14λbond for radiating into water,12λfor use with a fused silica delay medium). A 70 percent band width can be obtained with only 4 db loss per transducer.Confirming experimental results are described for delay lines using quartz crystals and one‐half wavelength plastic seals or one‐quarter wavelength solder seals. For the latter, band widths of 85 percent of midband frequency have been obtained. An efficient delay line usingBaTiO3transducers is also described.

ISSN:0001-4966    

DOI:10.1121/1.1907519

出版商:Acoustical Society of America    

年代:1955

数据来源: AIP

摘要:

The velocities of elastic waves in a laminated medium have been determined by calculating the effective elastic parameters and the effective density. The procedure is to assume the medium to be in static equilibrium and exposed to certain stresses. The stresses are of such a nature as to generate strains similar to those which would exist during the passage of an elastic wave through the medium. From the application of Hooke's law, an effective stiffness constant for the medium is obtained. The ratio of this effective stiffness to the effective density is the square of the velocity of the elastic wave. For a medium consisting of layers of two materials with the same density but with a velocity contrast of two (2), the velocity of compressional waves traveling parallel to the layering is 20 percent higher than the velocity of the same wave traveling perpendicular to the layers. TheSHshear wave has a velocity which is 25 percent higher than theSVshear wave for the same laminated medium.

ISSN:0001-4966    

DOI:10.1121/1.1907520

出版商:Acoustical Society of America    

年代:1955

数据来源: AIP

摘要:

The use of the ultrasonic pulse technique as a means of determining the elastic constants of polycrystalline aluminum at high temperatures has been considered in some detail.TheC11andC44elastic constants, Debye temperature, and Young's modulus were computed from the longitudinal and transverse velocity measurements. The variations of these constants with temperature showed the predicted linear decrease expected from solid state theory.

ISSN:0001-4966    

DOI:10.1121/1.1907521

出版商:Acoustical Society of America    

年代:1955

数据来源: AIP

摘要:

The ultrasonic resonator interferometer has been used to measure the ultrasonic velocity at 30°C in 1,1‐dichloroethane (ethylidene chloride,CH3CHCl2) and 1,2‐dichloroethane (ethylene chloride,CH2Cl‐CH2Cl) vapors as a function of frequency over pressure. The rangesf/pemployed are 0.8 to 100 Mc sec−1atmos−1in the case of ethylidene chloride and 1.0 to 100 Mc sec−1atmos−1in the case of ethylene chloride. The velocities have been corrected for nonideality of the two vapors. Dispersion of ultrasonic velocity occurs in both the cases and this is ascribed to the slow rate of energy exchange between translational and vibrational states. There is evidence of double relaxation in the two cases, the principalf/pratios at 30°C being 76.5 Mc sec−1atmos−1for the former and 102 Mc sec−1atmos−1for the latter.

ISSN:0001-4966    

DOI:10.1121/1.1907522

出版商:Acoustical Society of America    

年代:1955

数据来源: AIP

摘要:

The experiment of Laird, Taylor, and Wille (1932) showed that the reduction in the intensity of a sound required to produce half‐loudness is of the order of 20 db. Since this result is out of line with most other studies in this field, an attempt was made to repeat the experiment with a similar piece of apparatus (2‐A audiometer). The first attempt to copy the procedure of Laird, Taylor, and Wille gave results more like those usually obtained, namely, a required reduction for half‐loudness of the order of 10 db. A second experiment, involving the use of comparison tones placed as much as 40 db below the standard, gave results more like those of Laird, Taylor, and Wille. The method they used appears to be overly sensitive to the range and order of presentation of the comparison stimuli.

ISSN:0001-4966    

DOI:10.1121/1.1907523

出版商:Acoustical Society of America    

年代:1955

数据来源: AIP