摘要:

Developments in the field of ferroelectricity are traced from the discovery of the ferroelectric effect by Joseph Valasek in 1921 to its use in a variety of modern applications. Its appearance and utilization in different substances is discussed.

ISSN:0001-4966    

DOI:10.1121/1.1912765

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A method for computing nonlinear interactions between the spectral lines of progressive finite‐amplitude waves in homogeneous media is developed via Burgers' equation. By means of Fourier analysis, this equation is reduced to a coupled set of ordinary nonlinear differential equations, which are then solved recursively using Airy's algorithm. The solution thus obtained has the form of a vector which initially contains the spectral amplitudes of the source waveform and is subsequently enriched by nonlinearly generated spectral components as the signal propagates through the medium. The utility of the method consists in the ease with which it can be implemented on a digital computer and its applicability to a wide variety of source waveforms.

ISSN:0001-4966    

DOI:10.1121/1.1912766

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

An experimental study was made of the shock wave projected into free water from the end of a hydrodynamic conical shock tube driven by a high explosive. Pressure‐time measurements were made with small piezoelectric and piezoresistive gauges arrayed about two different shock tube configurations. For one tube, designed on a very small scale, results showed that a remnant of the sector shock front propagated undisturbed over the length of the water tank (20 cone lengths). This was demonstrated by the fact that attenuation with distance along the extended cone axis closely approximated the accepted relationshipP∝R−1.13for explosion shock waves in free water. On‐axis data for the other tube whose shock wave energy was three orders of magnitude greater than the first, showed very rapid attenuation beyond the cone mouth. Both cone results are consistent with existing theory that defines the undisturbed shock front region in terms of cone parameters—length, angle, and amount of explosive—that affect shock energy and geometry. Results for the first cone on attenuation of pressure with angle to the axis also were consistent with the predicted angular extent of the undisturbed front region. At 30°, attenuation was about 75%.

ISSN:0001-4966    

DOI:10.1121/1.1912767

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Over a decade of experience with velocimeters aboard deep submergence vehicles has demonstrated that accuracies of 0.1 m/sec or better can be obtained with proper procedures. Calibrations and distilled water equations are discussed, along with the new International Temperature Scale adopted in 1968. Calibration drift is described for three types of velocimeters to underscore that accuracy requires frequent calibrations as well as intercomparisons between several instruments during. deep dives. Pressure corrections are computed. Errors due to thermal lags of earlier velocimeters were observed while transmitting thermoclines. Laboratory measurements with a velocimeter in 50 gal of natural seawater of 27.405‰ salinity gave good results, closer to those of V. A. Del Grosso [J. Acoust. Soc. Amer.47, 947 (1970)], than to W. D. Wilson [J. Acoust. Soc. Amer.32, 1357 (L) (1960)].

ISSN:0001-4966    

DOI:10.1121/1.1912768

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The problem of transmission of acoustic waves through submerged orthotropic spherical shells was considered. The sound radiation in an infinite acoustic fluid is induced by a rigid spherical transducer, concentric within an orthotropic spherical shell having an axisymmetric surface‐velocity distribution. The space between the spherical transducer and the orthotropic spherical shell is full of the same acoustic fluid as that outside of the shell. The equations of motion for orthotropic shells, as well as for the fluid inside and outside, were derived. These equations are then solved by satisfying the continuity conditions on all solid‐fluid interfaces. Four representative transducer surface‐velocity distributions were considered. The solution for the farfield acoustic pressure was obtained for an orthotropic and for an isotropic shell.

ISSN:0001-4966    

DOI:10.1121/1.1912769

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The self‐acoustic radiation impedance of cap‐shaped and ring‐shaped pistons conformal to a rigid prolate spheroidal baffle and vibrating with uniform normal velocity is calculated using prolate spheroidal wave functions. The necessary spheroidal functions are obtained using recently developedFORTRANcomputer programs. Plots of the normalized radiation resistance and the normalized radiation reactance as functions of the acoustic size parameterhare presented for several different baffle shapes and relative piston sizes. The effect of the baffle size and curvature on the radiation impedance is shown to be small.

ISSN:0001-4966    

DOI:10.1121/1.1912770

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

This analytical study concerns the sensing of wide‐band pressure fields by moving receivers or sensors. Treated are linear kinematical aspects for ideal sensors that travel at constant subsonic or supersonic velocities. The fields are described in wave‐harmonic (wavenumber‐frequency) space. The sensed signal or noise components are related at their sensed frequencies and on a spectral basis. It is shown that the point sensor is no longer uniform or nondirective once it moves. Its directional pattern, and that of spatially extended sensors, too, depends upon the Mach number of sensor motion, upon the sensed frequency, and even upon the choice of a reference spectrum for the fields in the resting fluid. A certain compensation for the effects of motion is possible in directive sensors by adjustment of parameters. This compensation, however, is partial and permits only the preservation of some crucial feature. The adjustment is explained in terms of a “matched Mach number” for back‐nulled gradient and endfire‐line sensors. The definition of gain is amended, and the concept of the equivalent signals of sensed field components is recommended as a suitable measure of a sensing situation. Equivalent spectra of noise incident from the rear and of isotropic noise are presented for velocity‐matched back‐hulled gradient and endfire‐line sensors; depending upon frequency and reference spectrum, they differ from their rest values.

ISSN:0001-4966    

DOI:10.1121/1.1912771

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The distribution functions are considered for the random sampling in space of a three‐dimensional acoustic mode. These functions are of interest when it is desired to estimate either the total acoustic energy present in the space, from a finite number of sample values, or the driving‐point impedance at an arbitrarily chosen point. Expressions are obtained for the probability density function (pdf) and cumulative function for a single mode excited in an ideal elastic fluid in a right circular cylindrical enclosure. Two kinds of axisymmetric mode are considered, those corresponding to the first zeros of the zero‐ and first‐order Bessel functions. The distribution functions obtained are compared with those for modes in a rectangular enclosure [R. V. Waterhouse, J. Acoust. Soc. Amer.47, 961–967 (1970)], and exhibit some novel and interesting features. For the cylindrical modes, the pdf's differ for each order of one type of mode, and in general have discontinuities, the number of which increases with the mode number. In both these respects the cylindrical modes differ from the rectangular modes.

ISSN:0001-4966    

DOI:10.1121/1.1912772

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A device has been developed which allows the determination of the direction of shear particle motion generated by a single transducer. The normal ways of determining shear motion are to use another crystal of known polarization or to know the crystallographic geometry. This device analyzes the shear motion by use of reflection modes in a multiwaveguide assembly. The shear motion can be related to the geometry of this waveguide assembly.

ISSN:0001-4966    

DOI:10.1121/1.1912773

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The present letter discusses additional technical literature dealing with calculations of nearfield pressure induced by vibrating acoustic transducers.

ISSN:0001-4966    

DOI:10.1121/1.1912774

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP