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Leclercq M.,CNRS Acoustic Lab of Du Maine University | Picart P.,CNRS Acoustic Lab of Du Maine University | Picart P.,University of Limoges
Optics Express | Year: 2012

This paper presents a detailed analysis of the influence of the pixel dimension in digitally-recorded holograms. The investigation is based on both theoretical and experimental viewpoints for recordings beyond the Shannon limits. After discussing the pixel paradox, the sinc amplitude modulation is experimentally demonstration. The experimental analysis is well correlated to the theoretical basics; in addition, the filling factor of the sensor can be estimated. The analysis of the phase changes of the object show that they can be obtained with a very good contrast and that they are only limited by the decorrelation noise, as when the Shannon conditions are fulfilled. © 2012 Optical Society of America.

Fabre B.,CNRS Jean Le Rond d'Alembert Institute | Gilbert J.,CNRS Acoustic Lab of Du Maine University | Hirschberg A.,TU Eindhoven | Pelorson X.,CNRS GIPSA Laboratory
Annual Review of Fluid Mechanics | Year: 2011

We are interested in the quality of sound produced by musical instruments and their playability. In wind instruments, a hydrodynamic source of sound is coupled to an acoustic resonator. Linear acoustics can predict the pitch of an instrument. This can significantly reduce the trial-and-error process in the design of a new instrument. We consider deviations from the linear acoustic behavior and the fluid mechanics of the sound production. Real-time numerical solution of the nonlinear physical models is used for sound synthesis in so-called virtual instruments. Although reasonable analytical models are available for reeds, lips, and vocal folds, the complex behavior of flue instruments escapes a simple universal description. Furthermore, to predict the playability of real instruments and help phoneticians or surgeons analyze voice quality, we need more complex models.

Pagneux V.,CNRS Acoustic Lab of Du Maine University
Mathematics and Mechanics of Solids | Year: 2012

The effect of the free edge of a semi-infinite elastic cylinder with circular cross section is considered. It is shown that there exists a complex resonance frequency associated with an axially symmetric localized vibration near the free edge for every value of the Poisson ratio v. For two particular values of v, v = 0 and v = 0.1267, the imaginary part of the complex resonance frequency is zero which corresponds to a trapped mode of the semi-infinite rod. This resonance is also shown to be associated with two eigenfrequencies of the finite length cylinder. © 2011 SAGE Publications.

Ruello P.,CNRS Le Mans Institute of Molecules and Materials | Gusev V.E.,CNRS Acoustic Lab of Du Maine University
Ultrasonics | Year: 2015

In this review we address the microscopic mechanisms that are involved in the photogeneration processes of GHz-THz coherent acoustic phonons (CAP) induced by an ultrafast laser pulse. Understanding and describing the underlying physics is necessary indeed for improving the future sources of coherent acoustic phonons useful for the non-destructive testing optoacoustic techniques. Getting more physical insights on these processes also opens new perspectives for the emerging field of the opto-mechanics where lattice motions (surface and/or interfaces ultrafast displacements, nanostructures resonances) are controlled by light. We will then remind the basics of electron-phonon and photon-phonon couplings by discussing the deformation potential mechanism, the thermoelasticity, the inverse piezoelectric effect and the electrostriction in condensed matter. Metals, semiconductors and oxide materials will be discussed. The contribution of all these mechanisms in the photogeneration process of sound will be illustrated over several examples coming from the rich literature. © 2014 Elsevier B.V. All rights reserved.

Leclere Q.,INSA Lyon | Pezerat C.,CNRS Acoustic Lab of Du Maine University
Journal of Sound and Vibration | Year: 2012

This paper addresses the problem of the location and identification of vibration excitations from the measurement of the displacement field of a vibrating structure. It constitutes an improvement of the force analysis technique published several years ago. The development is based on the use of the motion equation which is discretized by finite difference schemes approximating spatial derivatives of the displacement. In a first instance, the error due to this approximation is analytically calculated in the case of beams and the low-pass filtering effect of the finite difference schemes in the wavenumber domain is shown. This filter also contains singularities implying bias errors, especially if the spacing between sensors is chosen in order to regularize the problem. In a second instance, a corrected value is applied to the classic schemes used in the force analysis technique, which suppresses completely the singularities of the filter. After the complete description of the corrected force analysis technique on beams, the extension to plates is described, where simulations with noisy data show the very good accuracy one can obtain without the requirement of an added regularization for the excitation identification. © 2011 Elsevier Ltd All rights reserved.

The numerical computations of thermoviscous acoustics consist of multi-physics and multiscale modeling, combining acoustic propagation at the wavelength scale and momentum and heat transfers at the scale of boundary layer thicknesses. The coupled linear formulation based upon particle velocity and the temperature variation variables is easily implemented using the finite element method. Because acoustic wavelength and boundary layer thicknesses have very different length scales, anisotropic and adaptive meshing is used to optimize the node distribution on the mesh. When combined, the Finite Element Method using degrees of freedom for particle velocity and temperature variation and anisotropic, adaptive meshing technique give the opportunity for accurate numerical solutions at reasonable computational cost. In order to show the potential of the method, this numerical procedure is applied to axisymmetrical and bidimensional models, illustrating the ability to compute, for complete devices, both propagation and diffusion processes. The physics of the numerical solution is briefly discussed near the discontinuity of a duct and close to the end of a stack inserted in a resonant cavity. © S. Hirzel Verlag.

Ourir A.,Laue Langevin Institute | Maurel A.,Laue Langevin Institute | Pagneux V.,CNRS Acoustic Lab of Du Maine University
Optics Letters | Year: 2013

A realization of a reflectionless power splitter is proposed by use of a metamaterial junction. To design the junction, the electromagnetic wave transmission in multiple connected leads is investigated theoretically and numerically. A closed analytical form is derived for the scattering matrix of any geometry of the interconnected leads. We show that the use of a junction made of ∈-near-zero (ENZ) material allows production of perfect transmission. This can be achieved by reducing the area of the ENZ junction (squeezing effect) and by tuning the widths of the output leads with respect to the input lead. It is also shown that the same effect is obtained without squeezed junction by using a match impedance zero index material (MIZIM junction). © 2013 Optical Society of America.

Gusev V.E.,CNRS Acoustic Lab of Du Maine University | Wright O.B.,Hokkaido University
New Journal of Physics | Year: 2014

We present an acoustic metamaterial for flexural waves with both negative density and elastic modulus. By means of an analytical lumped-element approach, we introduce a combination of resonant elements on the surface of a plate. Following on from experimental demonstrations and theoretical work, negative density is achieved by introducing elements such as stubs that involve normal-force interactions, whereas negative modulus is achieved by introducing new types of resonant element that involve lateral forces and rotational inertia. Our approach therefore opens the way for the realization of double-negative acoustic meta-plates to control flexural waves. Applications include cloaking and filtering. © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

MacAluso C.A.,2611 SW Greenwich Way | Dalmont J.-P.,CNRS Acoustic Lab of Du Maine University
Journal of the Acoustical Society of America | Year: 2011

This paper presents a mathematical design methodology for determining the shape of a trumpet air column that has near-perfect harmonicity, whose components are discontinuity-free, and whose input impedance peak heights are balanced over the playing range. The simulation model employed assumes linear wave propagation and uses cylindrical element discretization with a plane wave approximation. Acoustic measurements are made using a test set-up with an estimated relative measurement error of 3 cents. Comparisons of measured results are given for the presented design (Macaluso trumpet) and the same trumpet air column with the bell replaced by a commercially used generic trumpet bell of unknown shape (Generic trumpet). For acoustic resonance modes 2-13 (233-1515 Hz), the measured root-mean-square (rms) harmonicity deviation is 5 cents for the Macaluso trumpet, whereas it is 18 cents for the Generic trumpet. However, considering the estimated measurement uncertainty, each of those deviations is somewhat over-stated. For that same range of resonances, the rms deviation between measured and calculated resonance frequencies for the Macaluso trumpet is 3 cents, thus validating the presented simulation model and equations. © 2011 Acoustical Society of America.

Renou Y.,CNRS Acoustic Lab of Du Maine University | Auregan Y.,CNRS Acoustic Lab of Du Maine University
Journal of the Acoustical Society of America | Year: 2011

This paper deals with experimental investigation of the lined wall boundary condition in flow duct applications such as aircraft engine systems or automobile mufflers. A first experiment, based on a microphone array located in the liner test section, is carried out in order to extract the axial wavenumbers with the help of an high-accurate singular value decomposition Prony-like algorithm. The experimental axial wavenumbers are then used to provide the lined wall impedance for both downstream and upstream acoustic propagation by means of a straightforward impedance education method involving the classical Ingard-Myers boundary condition. The results show that the Ingard-Myers boundary condition fails to predict with accuracy the acoustic behavior in a lined duct with flow. An effective lined wall impedance, valid whatever the direction of acoustic propagation, can be suitably found from experimental axial wavenumbers and a modified version of the Ingard-Myers condition with the form inspired from a previous theoretical study [Aurégan, J. Acoust. Soc. Am. 109, 59-64 (2001)]. In a second experiment, the scattering matrix of the liner test section is measured and is then compared to the predicted scattering matrix using the multimodal approach and the lined wall impedances previously deduced. A large discrepancy is observed between the measured and the predicted scattering coefficients that confirms the poor accuracy provided from the Ingard-Myers boundary condition widely used in lined duct applications. © 2011 Acoustical Society of America.

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