Radiation efficiency of a distribution of baffled pistons with arbitrary phases.

The radiation resistance and efficiency of a collection of circular pistons, randomly placed on a plane and vibrating with arbitrary phases, are expressed as a combination of the self- and mutual-radiation components. We use the first product or bridge theorem to construct the directivity pattern of this type of arrangement and the radiation properties are calculated according to Bouwkamp's impedance theorem. To illustrate the versatility of our approach, we refer to special cases for symmetric arrangements, for example, to compare with the modal radiation efficiency in structures having "regular" modal patterns.

A transverse isotropic equivalent fluid model combining both limp and rigid frame behaviors for fibrous materials.

Due to the manufacturing process, some fibrous materials like glasswool may be transversely isotropic (TI): fibers are mostly parallel to a plane of isotropy within which material properties are identical in all directions whereas properties are different along the transverse direction. The behavior of TI fibrous material is well described by the TI Biot's model, but it requires one to measure several mechanical parameters and to solve the TI Biot's equations. This paper presents an equivalent fluid model that can be suitable for TI materials under certain assumptions.

Effectiveness of nonporous windscreens for infrasonic measurements.

This paper deals with nonporous windscreens used for reducing noise in infrasonic measurements. A model of sound transmission using a modal approach is derived. The system is a square plate coupled with a cavity.

A homogenization method used to predict the performance of silencers containing parallel splitters.

An analytical model based on a homogenization process is used to predict and understand the behavior of finite length splitter/baffle-type silencers inserted axially into a rigid rectangular duct. Such silencers consist of a succession of parallel baffles made of porous material and airways inserted axially into a rigid duct. The pore network of the porous material in the baffle and the larger pores due to the airway can be considered as a double porosity (DP) medium with well-separated pore sizes.

Static model of a violin bow: influence of camber and hair tension on mechanical behavior.

Experienced bow makers empirically know the influence of wood, tapering, and camber on the playing and tonal qualities of a bow. However, the way each parameter affects the bow mechanical behavior is not clearly established. An in-plane finite element model is developed to highlight the link between the adjustable design parameters and the mechanical behavior of a bow.

Ironless transducer for measuring the mechanical properties of porous materials.

This paper presents a measurement setup for determining the mechanical properties of porous materials at low and medium frequencies by extending toward higher frequencies the quasistatic method based on a compression test. Indeed, classical quasistatic methods generally neglect the inertia effect of the porous sample and the coupling between the surrounding fluid and the frame; they are restricted to low frequency range (<100 Hz) or specific sample shape. In the present method, the porous sample is placed in a cavity to avoid a lateral airflow.

On the use of a loudspeaker for measuring the viscoelastic properties of sound absorbing materials.

This paper investigates the feasibility to use an electrodynamic loudspeaker to determine viscoelastic properties of sound-absorbing materials in the audible frequency range. The loudspeaker compresses the porous sample in a cavity, and a measurement of its electrical impedance allows one to determine the mechanical impedance of the sample: no additional sensors are required. Viscoelastic properties of the material are then estimated by inverting a 1D Biot model.

Validity of the limp model for porous materials: a criterion based on the Biot theory.

The validity of using the limp model for porous materials is addressed in this paper. The limp model is derived from the poroelastic Biot model assuming that the frame has no bulk stiffness. Being an equivalent fluid model accounting for the motion of the frame, it has fewer limitations than the usual equivalent fluid model assuming a rigid frame.