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The prediction of acoustic propagation from a monofrequency coherent line source in a cutting with impedance boundary conditions over a noise-screen onto surrounding flat grassland is presented. It is well known that over flat ground the spectra for single-noise screens have significant marked differences for propagation over absorbing ground where the screen obstructs surface wave attenuation ove

in this paper, the problem of diffraction of a spherical wave by a hard half-plane is considered. The starting point is the Biot-Tolstoy theory of diffraction of a spherical wave by a fluid wedge with hard boundaries. In this theory, the field at a point in the fluid is composed eventually of a geometrical part: i.e., a direct component, one or two components due to the reflections on the sides of

The stability properties of a periodically loaded non-linear dynamic system are investigated and special attention is given to damping effects. Advantage is taken of the Floquet theory and the FE-approach is applied to a hinged beam where the damping is described by a standard material model and where even damping effects at the hinges are considered. Comparisons are made with experimental results

In this short note, some experimental results are presented on the diffraction of a spherical way by a hard half-plane. This study was conducted with the aim to give evidence to the existence of the edge-diffracted wave. The sound source used in this experimental study is a condenser microphone operating in a reverse way. The wave emitted by a sound source propagates in space and hits a thin alumi

An image solution for the forced response of a clamped finite beam is developed. The finite beam is replaced by an infinite beam under spatially periodic excitation and periodic support reactions. The response is then found by a Fourier transform approach, making use of the periodicity. An explicit expression is found, using the Poisson sum formula. The aim is to describe the potential of using th

A dynamic beam system loaded harmonically in the axial direction and constrained in the transverse direction is modelled using different theoretical descriptions. Results from an experimental set-up are compared to calculations using Bernoulli as well as Timoshenko beam theories. Some results from investigations of this beam system unveiling its chaotic nature have earlier been presented, but here

A method to determine the dynamic load between two rotating elastic helical gears is presented. The stiffness of the gear teeth is calculated using the finite element method and includes the contribution from the elliptic distributed tooth load. To make sure that the new incoming contacts which are the main excitation source are properly simulated, the necessary deformation of the gears is determi

The undamped natural vibrations of a constrained linear structure are given by the solutions to a generalized eigenvalue problem derived from the equations of motion for the constrained system involving Lagrangian multipliers. The eigenvalue problem derived is defined by the mass matrix of the unconstrained structure and a non-symmetric and singular stiffness matrix for the constrained system. The

A method is described which can be used to calculate dynamic gear tooth force and bearing forces. The model includes elastic bearings. The gear mesh stiffness and the path of contact are determined using the deformations of the gears and the bearings. This gives contact outside the plane-of-action and a time-varying working pressure angle. In a numerical example it is found that the only important

In a structural modification problem the mass and stiffness matrices are modified to obtain a desired spectrum. In this paper, this is done by imposing constraints on the structure. The undamped natural vibrations of a constrained linear structure are calculated by solving a generalized eigenvalue problem derived from the equations of motion for the constrained system involving Lagrangian multipli

Scattering from an acoustically soft elliptic disk is treated by means of the null field approach. It is shown that in the disk limit of a general ellipsoid the relevant matrix elements have a well-defined limit, and that the formulation is attractive for numerical calculations. In a separate section the low frequency expressions of the total cross section and the far field amplitude are also deri

A boundary integral equation is described for the prediction of acoustic propagation from a monofrequency coherent line source in a cutting with impedance boundary conditions onto surrounding flat impedance ground. The problem is stated as a boundary value problem for the Helmholtz equation and is subsequently reformulated as a system of boundary integral equations via Green's theorem. It is shown

Within recent years, there has been a renewed focus on sound in urban environments. From sound installations in public space to sound festivals in alternative settings, we find a common interest in sound art relating to the urban environment. Artworks or interventions presented in such contexts share the characteristics of site specificity. However, this article will consider the artwork in a broa