摘要:

A new method is presented for the analysis and utilization of linear and nonlinear response data obtained from structural elements under conditions of acoustical loading. It is found that due to phase angle differences, the significance of resonance response lies in the amplification of bending stresses, regardless of secondary tension forces induced at the constraints. Comparisons are presented with values so calculated. Correlation of an equivalent linear system possessing the theoretical amplification factor with a nonlinear system of known behavior (determined by tests) is demonstrated. This correlation is also useful in transforming sinusoidal test data to random response, thereby rendering a better application of the cumulative damage rule in sonic‐fatigue expectancy calculations for aerospace‐vehicle structures.

ISSN:0001-4966    

DOI:10.1121/1.1918289

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Elastic‐wave propagation in a porous, saturated elastic solid is investigated for the situation in which there is a uniform flow velocityU0in the fluid. Wave‐velocity equations are set up forPandSwaves, and the case of no viscous fluid coupling is investigated in detail.

ISSN:0001-4966    

DOI:10.1121/1.1918291

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

A set of nonlinear equations describing the vibrations of sandwich plates is derived. These equations are then applied to a plate vibrating in plane strain and to a rectangular plate; with the boundary edges assumed to be hinged in both cases. It is shown that the nonlinear frequencies increase with the amplitude of vibration. It is shown also that transverse shear deformations play an important role; however the effect produced by these deformations decreases with increasing amplitudes of vibration.

ISSN:0001-4966    

DOI:10.1121/1.1918293

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

In this paper there is derived a set of approximate equations governing the extensional motion of a sandwich plate, together with the associated initial and boundary conditions. Both the sandwich core and the facings are assumed homogeneous and isotropic, and the facings are assumed thin and identical to each other. The coupling effect of the thickness deformation of the core is considered in the derivation.Frequency‐wavelength curves are then obtained from these equations for an infinite plate in plane strain. The corresponding curves for the same plate according to the three‐dimensional exact theory of elasticity are also obtained. These two sets of curves are then used as a basis for discussion of the accuracy of the approximate equations.The curves indicate that for commonly used core materials and for wavelengths about three times the plate thickness and longer, the approximate equations are reasonably good up to frequencies somewhat higher than the fundamental thickness‐stretch frequency of the plate.

ISSN:0001-4966    

DOI:10.1121/1.1918295

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Often, well‐designed arrays of electroacoustic transducer elements radiating into water exhibit erratic behavior in the transmission‐frequency band such that the distribution of magnitude and phase of element velocities across the array appears to be independent of the distribution of electrical driving voltages or currents. Even at low drive levels, directivity patterns and source levels deteriorate, and some elements may even experience structural failure because of excessive motion of the radiating face. The cause of this unsatisfactory behavior is diagnosed and relatively simple curative measures are presented. In particular, the cure requires a separate tuning reactor for each element. The reactors are identical, but must be selected by a new criterion. If modular drive is used, the drivers must have a very low or a very high internal impedance, depending on circumstances.

ISSN:0001-4966    

DOI:10.1121/1.1918297

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Experimental and theoretical interference patterns, resulting from the interaction between signals arriving by a direct and by a surface‐reflected path, are compared for three receiver depths at frequencies of 530 and 1030 cps. Propagation losses are computed on the basis of ray theory for a velocity‐depth profile consisting of three linear segments. Agreement between ray theory and experiment is excellent at ranges less than that of the first shadow zone or the first caustic. Theoretical losses based on the assumption of isovelocity water also agree well with experiment at the shorter ranges, but can depart markedly at longer ranges in the interference pattern because of the effect of refraction on both travel time differences and component amplitudes.

ISSN:0001-4966    

DOI:10.1121/1.1918299

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

A piston‐type resonant element for use in underwater sound‐transducer arrays is described. The acoustic loading on the piston is varied by the use of a shallow cavity. The element is stable under high hydrostatic pressure, and its efficiency is higher than 90% over a broad bandwidth. An equivalent circuit that successfully reproduces the measured characteristics of the transducer is developed.

ISSN:0001-4966    

DOI:10.1121/1.1918301

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The ability of human observers to detect signals that are bursts of white noise is measured by two experimental procedures. In both procedures, the observer's task is to select the interval containing the signal from the two temporal intervals, marked by lights, which constitute a trial. In the first, the signal is added to a continuous background of white noise; in the second, the signal is added to one or the other of two equal noise bursts, that are added to the continuous background noise during the observation intervals.The psychometric functions obtained in the two experimental conditions are different. In the first experimental condition the psychometric functions are consistent with the assumption that the observer is uncertain about either the exact time when the signal occurs or its exact duration, or about both. In the second procedure, in which two noise bursts mark the observation intervals, the psychometric functions are consistent with the prediction of a statistical‐decision model that assumes exact knowledge of the temporal occurrence of the signal. In this second procedure the signal to noise ratio for some constant level of detectability is considerably affected by the relation between the continuous background noise and the level of the two noise bursts. The minimum value of signal‐to‐noise ratio occurs when the continuous noise is ∼5–10 dB more intense than the equal noise bursts; the signal to noise ratio increases from this minimum as the background level is changed in either direction.

ISSN:0001-4966    

DOI:10.1121/1.1918303

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The results of audiometric and various speech tests of persons with normal and different degrees of nerve‐type hearing impairment are reported. Correlation regression coefficients (“beta” weights) were found between the hearing loss measured at a number of pure‐tone frequencies and the speech test results. These beta weights indicate that taking the average of the decibel hearing loss at either 2000, 3000, and 4000 cps or at 1000, 2000, and 3000 cps provides a reasonably adequate rank‐order indicator of the ability to understand speech. The relation between our results and other studies are discussed; it is suggested that some speech tests and methods of scoring that have been used in experiments of this type in the past introduce a bias that leads to an underestimation of the importance of auditory acuity at frequencies above 2000 cps.

ISSN:0001-4966    

DOI:10.1121/1.1918305

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The residue phenomenon makes it necessary to assume that many areas of the basilar membrane may give rise to sensations of widely different pitch, depending upon the pattern of stimulation. In the case of steady‐state signals, the place of maximal stimulation will be a measure of timbre whereas the pitch will depend on the quasi‐periodicity of the signal. A closer study of the residue phenomena is of interest, since the residue implies situations where average frequency and periodicity are separate parameters and, to a certain extent, may be varied independently. The literature shows that attempts to establish the residue have not always been successful, mostly due to the specific frequency combinations chosen. In this paper, measurements are described on an harmonic complex consisting of three components, with variable modulation depth and frequency. This harmonic complex is found to have a decidedly tonal character within a limited frequency region. The boundaries for a complex with a modulation depth of 100% are roughly given by values of the center frequencyf<5000 cps, and values of the spacing frequencyg⩾0.05f. A theoretical model of a pitch‐extractor is presented which accounts for the observed frequency region of the tonal residue.

ISSN:0001-4966    

DOI:10.1121/1.1918307

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP