Showing papers in "Journal of Sound and Vibration in 1969"

TL;DR: In this article, the transverse displacement of a three-layer sandwich beam with a viscoelastic core is derived in terms of the transversal displacement, w, for a 3D beam.

TL;DR: In this paper, a simplified model is used to study the implications of this real situation from a consideration of the vibration levels which these components might suffer in practice, and an optimum arrangement of typical blades is proposed.

TL;DR: In this paper, a statistical energy analysis is used to predict the sound transmission loss, the radiation resistance and the vibration amplitude of a partition, and agreement between theory and experiment is shown to be good.

TL;DR: In this paper, the authors extended the theory of sound generation by multibladed single-stage fans operating in a free field and showed that the quadrupole effects are important for low-speed, few-bladed fans in the first harmonics.

TL;DR: In this article, the authors derived the linearized wave-equation for two-dimensional viscous flow with and without shear in ducts with finite wall admittance, using a constant gradient and a turbulent velocity profile.

TL;DR: In this article, a comprehensive theoretical study of the problem of helicopter rotor noise radiation is presented, which includes blade slap, rotation noise and vortex noise effects, including all effects of fluctuating airloads and all possible rigid and flexible blade motions.

TL;DR: In this paper, a brief survey of the transfer matrix method of analyzing the dynamic behavior of beam structures is presented for single rows of aircraft panels which are continuous over supporting stringers.

TL;DR: In this article, the authors used Kirchhoff's theorem to measure the acoustic power radiated from a turbulent boundary layer in terms of the cross spectral density of the pressure field over a rigid plane surface.

TL;DR: In this article, the rotational noise is the dominant rotor noise mechanism and neglects vortex noise as being an appreciable noise source at normal operating conditions, which can be adopted to suit any free-field rotary momentum changing device.

TL;DR: In this paper, the transition points to line source or plane source behavior of the sound attenuation with distance are shown to be simply related to the characteristic dimensions of the source, which can be used to make a universal attenuation template.

TL;DR: In this paper, a rigid rectangular box with one simply-supported flexible wall is analyzed by numerical and statistical methods for the internal acousto-structural mode coupling factors and the corresponding modal average radiation efficiency.

TL;DR: In this paper, the statistical properties of the wall pressure field determined from these recordings included the power spectral density, space-time correlations, and convection speeds embracing both broad and narrow (third-octave) frequency bands.

TL;DR: In this paper, a theory was developed that predicts the variation with frequency of the acoustic impedance of a panel sound absorber, taking into account the mass, stiffness and internal damping of the panel; the stiffness of the cavity; and also the effect of introducing a porous material into the cavity.

TL;DR: In this paper, the partial differential equation of motion of a finite-length cylindrical sandwich shell with a viscoelastic core layer is derived, and the solution of this differential equation subject to satisfying the boundary conditions, which have been discussed in detail, yields the frequency equation and corresponding composite loss-factors.

TL;DR: In this article, the radiation efficiency of higher-order acoustic modes in a baffled annular opening was analyzed. And the variation of radiation efficiency with frequency was generalized in terms of mode cut-off.

TL;DR: Theoretical results showing the effect of various parameters on the transmission loss of multilayer constructions are also discussed in this paper, with the only discrepancies occurring with multiple panels having large air gaps.

TL;DR: In this article, the effect of fluid flow on the modal cut-off frequencies was investigated and rather complete details of the various methods of detecting the frequencies are given because of the lack of any such description in the literature.

TL;DR: In this article, a method for the experimental determination of the rotating acoustic modes that may be generated, at the blade-passing frequencies, in the inlet duct of an axial fan or compressor is presented.

TL;DR: In this article, the response of a damped mass spring system to an N wave is examined in terms of dynamic magnification factors which are expressed as functions of the non-dimensionalized frequency fτ.

TL;DR: In this article, a line standing wave tube of variable rectangular cross-section is compared with an approximate solution of Scott's equation, and a method of measurement of the characteristic impedance ratio and complex propagation constant in the bulk of the lining material is described.

TL;DR: In this paper, the vibrations of cylindrical shells, consisting of two sections of different thicknesses but with a common mean radius, have been investigated, and the changes in natural frequency and mode shape for various modes of a shell of constant length were given.

TL;DR: In this paper, a mechanical vibrator has been developed to generate the bubbles at controlled sizes and densities, and the measurements suggest that the well-known signals at subharmonics of the fundamental are caused by forced radial oscillation of bubbles that are resonant at the subharmonic frequencies.

TL;DR: In this paper, approximate expressions for the acoustic admittance of baffled openings under the following conditions: (i) openings of arbitrary shape, sound wavelength larger than the opening dimensions; (ii) slit-shaped openings, sound wavelengths larger than narrow dimension.

TL;DR: In this article, the sound pressure levels of the bangs corresponded to the indoor stimulation experienced for outdoor sonic bangs of 0·80 lb/ft 2 to 2·53 lb /ft 2.

TL;DR: In this paper, the absolute threshold of hearing for octave bands of noise with center frequencies from 125 to 4 Hz has been determined and the results show that the noise threshold behaves in a similar fashion to the tone threshold, but below 32 Hz noise thresholds are more sensitive by a small but significant amount.

TL;DR: In this paper, the responses of part of the fuselage of a typical supersonic transport to turbulent boundary layer noise for two flight speeds, and to reverberant noise, are computed by the classical modal approach.

TL;DR: In this paper, an alternative finite difference formulation of the governing differential equation of the title problem was proposed, which was used over the entire range of symmetric supports (viz. four-corner supports to one single central support).

TL;DR: In this paper, a method of analysis is presented for determining the natural frequencies of multispan horizontally curved girders used in bridge structures and the use of the method is illustrated by developing the frequency equation for a two-span curved girder.