摘要:

By a power series expansion method an expression for the radiation potential of a circular piston mounted in an infinite baffle is derived. All points of the piston vibrate in phase and with equal amplitude in an infinite medium characterized by wavelength λ. The series expression is shown to be convergent at the surface of the piston (Z=0) whenka⩾20, andr100. ForZ≫a, the Schoch expression is obtained.

ISSN:0001-4966    

DOI:10.1121/1.1907691

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The geometrical theory of diffraction is described. It is used to determine the diffracted fields in inhomogeneous media. Cases in which such media contain smooth convex bodies are treated. The theory employs an extension of Fermat's principle which yields diffracted rays. By energy considerations the field associated with each ray is calculated. This calculation requires the introduction of diffraction coefficients and decay exponents. General formulas for these quantities are given in terms of local properties of the medium and of the body.In the companion article “Asymptotic theory of diffraction in inhomogeneous media” these problems are considered as boundary value problems. They are solved exactly and the solutions are expanded asymptotically for high frequencies. In all cases the asymptotic expansions agree completely with the corresponding results derived by the geometric theory, thus verifying this theory.

ISSN:0001-4966    

DOI:10.1121/1.1907692

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Some boundary value problems are considered for the reduced wave equation in media having planar or cylindrical stratification. They are solved exactly and the solutions are expanded asymptotically for high frequencies by using the method of stationary phase in conjunction with the WKB method and the Watson transformation. The asymptotic expansions are compared with the corresponding diffracted fields found by using the geometrical theory described in the companion article “Geometrical theory of diffraction in inhomogeneous media.” In all cases the asymptotic expansions agree completely with the corresponding results derived by the geometrical theory, thus verifying this theory.

ISSN:0001-4966    

DOI:10.1121/1.1907693

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The distributions of axial and radial vibration on the plane surfaces of short solid cylinders (disks) of barium titanate were experimentally determined for a number of modes. A vibration mode chart was prepared, to relate the types and frequencies of the prominent modes to the cylinder size and geometry. The electrical and mechanical aspects of the disk vibration indicate that there is no simple relationship between the electrical and mechanical measurements that are indicative of vibration amplitudes in different modes. A tentative explanation of this phenomenon is suggested by the experimentally disclosed existence of circulating currents in the disk electrodes.

ISSN:0001-4966    

DOI:10.1121/1.1907694

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

If an equipment item is supported on a low‐frequency mounting, there must be sufficient space allowance around the item to permit unrestricted vibratory motion. Also, the motion of the equipment item must be within the allocated travel of the mount. If the system is linear, the required space can be computed for random motion by the application of Fourier series. The solution includes motion of the adjacent structure and phase angles. After a review of basic random theory showing the application of random theory to design, an expression is developed for calculating the space required for an equipment item to vibrate. A numerical example is included to illustrate a method for estimating structural response and structural phase.

ISSN:0001-4966    

DOI:10.1121/1.1907695

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

This paper describes a procedure for calculating the frequencies of free vibration of plates composed of bonded, thin elastic laminae. The problem is reduced to the calculation of composite elastic parameters and the transposition of results from corresponding single‐layer plate problems. The vibration is assumed to be governed by the Poisson‐Kirchhoff theory of flexure, omitting the effects of transverse shear deformation and rotary inertia.

ISSN:0001-4966    

DOI:10.1121/1.1907696

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

A direct measurement of the acoustic ratioQ—i.e., the ratio of reverberant sound energy density in an enclosure to the direct sound energy density—by a correlation technique is shown to be possible. Results of such measurements in several rooms are found to agree fairly well with values obtained from the reverberation time through the formulaQ = 4πTR2/13.8V, which is based on the Sabine theory of the diffuse reverberant sound field.

ISSN:0001-4966    

DOI:10.1121/1.1907697

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

A study of the effect of random background noise on the intensive difference limen (DL) for pure tones was made by a method similar to that developed by Riesz. Three frequencies (250, 1000, and 4000 cps) at three sensation levels (20, 40, and 60 db) were studied, with signal‐to‐noise ratios of −15, −10, 0, and 10 db present for each condition. Analysis of the data revealed only signal‐to‐noise ratio as a significant factor affecting the DL. Repetition of the experiment with the psychophysical method of average error, for a 1000‐cps signal at levels of 10, 30, 50, and 70 db, and signal‐to‐noise ratios of −10, 0, 10, and 20 db resulted in a lack of systematic shift of the difference limen. The curve relating the difference limen obtained by modulation to signal‐to‐noise ratio appears to parallel that found in quiet when the difference limen is plotted against sensation level. Some hypotheses relating to the differences of psychophysical procedure are stated.

ISSN:0001-4966    

DOI:10.1121/1.1907698

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1907700

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The lower limit of intensity for demonstrating residual effects at low noise levels is a decreasing function of the pre‐exposure duration.

ISSN:0001-4966    

DOI:10.1121/1.1907701

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP