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Double layer structures consisting of stainless steel and polymer rods are designed to blur and attenuate Bragg and Bloch-Floquet scattering from a periodically ribbed plate in a given frequency bandwidth. These structures can be considered as ribbed plate-spring-mass systems, the resonance frequencies of which are obtained from random and circular permutations of five basic oscillators. Analytical and finite element methods are used to find their parameters and tank tests have been carried out to ensure the accuracy of the numerical results and validate the relevance of such a model. It has been found that the typical features associated with the periodicity of the ribs are replaced by a “Christmas tree” appearance when the far field pressure backscattered from the model is displayed in the (frequency, aspect angle) plane. An analysis of backscattering patterns is presented and comparisons with Naval Research Laboratory results are made.Double layer structures consisting of stainless steel and polymer rods are designed to blur and attenuate Bragg and Bloch-Floquet scattering from a periodically ribbed plate in a given frequency bandwidth. These structures can be considered as ribbed plate-spring-mass systems, the resonance frequencies of which are obtained from random and circular permutations of five basic oscillators. Analytical and finite element methods are used to find their parameters and tank tests have been carried out to ensure the accuracy of the numerical results and validate the relevance of such a model. It has been found that the typical features associated with the periodicity of the ribs are replaced by a “Christmas tree” appearance when the far field pressure backscattered from the model is displayed in the (frequency, aspect angle) plane. An analysis of backscattering patterns is presented and comparisons with Naval Research Laboratory results are made.

In the domain of renewable energies, marine current turbines constitute one of the possibilities of producing electrical energy. Naked-eye inspection, or with the aid of video monitoring systems of these machines to ensure their perfect working order, can be difficult in a turbid environment. Acoustic methods are conceivable. The study focuses on the blades of these machines, by considering rectangular plates. The propagation of Lamb waves in a plate is studied by analyzing experimental time signals obtained from acoustic scattering. These signals are analyzed employing the ray theory. In vacuum, the flexural wave is the A(0) Lamb wave, whilst in water this wave splits in a bifurcation: the A wave with a phase velocity always smaller than the sound speed in water, and the A(0) wave with a phase velocity always higher than the sound speed in water. In the central bandpass of the transducers used in the experiments, mainly the A and S(0) waves exist. However, signals observed in the third harmonic bandpass of the transducers are also analyzed. In order to complement these results, resonance frequencies of the plate studied are calculated taking into account the boundary conditions and compared with the resonance frequencies of the experimental spectra.

The problem of a plane acoustic wave scattered by a layered cylinder submerged in water is considered. This cylinder consists of a tube made of aluminum with a solid Lucite cylinder concentrically fitt inside it. These two components are coupled by a thin layer of water. A particular investigation is made on the influence of the thickness of the water layer on the presence of the bending wave A on the tube and the Scholte–Stoneley wave on the cylinder. The presence of these waves is examined in the function of the varying water layer thickness: two special cases are discussed. First, for a layer thickness greater than the tube thickness, it is shown that both the A wave on the aluminum tube and the Scholte–Stoneley wave on the Lucite cylinder are generated. Second, for a thickness much smaller than the tube thickness, a different wave is generated, which is a combination of both waves. These two cases are experimentally verified in a setup that employs a short pulse method.

A modal theory is developed for investigating the acoustic scattering by elastic cylinders of arbitrary cross section immersed in a fluid. Numerical results are presented for a plane wave incidence normal to the axis of an elliptical cylinder but arbitrary with respect to the noncircular cross section. Experimental results are obtained for an aluminum elliptical cylinder with the use of an impulse method. Comparisons between theoretical and experimental data are performed in the broad frequency range 8.5⩽ka⩽30 (k is the wave number in the fluid and a the major axis radius of the elliptic cylinder). The experimental observations are in good agreement with the theoretical predictions.

The acoustic scattering from an elastic elliptic cylinder immersed in water and excited by a normally incident plane wave is considered in this paper. The purpose is to determine, theoretically and experimentally, the pressure scattered by this cylinder. A model based on the theory of elasticity is described briefly. It consists in carrying out expansions in Fourier series of the expressions relating to the conditions of continuity (displacements and constraints) at the surface of cylinder. These expressions form a system of equations. The resolution of this system enables us to obtain the scattering coefficient, then the pressure scattered by the cylinder. The numerical results obtained from this model are compared with experimental results obtained by means of an experimental short-pulse method presented in the literature. An good agreement between the results is noted.

Forward acoustic scattering of an immersed solid LINE (cylinder bounded by hemispherical endcaps) in water is investigated in our study. The object is made of stainless steel and its L/2a ratio is equal to 2 (L: Length of the cylinder part and a: the radius is equal to 60 mm). An impulse measurement method is used in the experimentation. Most of results are obtained experimentally, in bistatic configuration. Mobile receiver transducer is located in a distinct position from the emitter. The polar diagram patterns of the scattered pressure shows an important amplitude of pressure in the shadow side of this object. Analysis of this phenomenon is based on theoretical and experimental results obtained for a sphere with the help of elasticity theory. Moreover, this study relies on the grey-level representation of the angular position of the receiver in function of recorded time signals. Thus on forward acoustic time signals, it is possible to identify echoes due to propagation paths of waves on this object.

The complex eigenfrequencies of a fluid-immersed evacuated infinite cylindrical shell, when plotted in the complex frequency plane, can be grouped into families corresponding to different types of circumferential waves. The dispersion curves versus frequency of the phase velocities of these circumferential waves are analogous to those of the Lamb waves on a plate A0, A1,… and S0, S1,…, but contain an additional branch reminiscent of the fluid-borne Scholte–Stoneley wave. This branch together with the A0-analog forms an interacting pair of dispersion curves A0+ (upper branch) and A0− (lower branch) which exhibit a repulsion phenomenon near the ambient fluid sound speed. Results of a recent numerical study of this phenomenon are here explained by perturbation theory, showing that during repulsion the wave character gets exchanged so that at frequencies above repulsion A0+ is a flexural and A0− a fluid-borne wave, and vice versa below repulsion.

International audience

Acoustic scattering from an absorptive cylinder (Lucite) of infinite length excited by a normal plane acoustic wave is investigated in low frequencies. This one is assumed to be homogeneous and isotropic in its viscoelastic properties. The experimental results are obtained with a method of isolation and identification of resonances (MIIR). The resonance spectra are particularly studied. In the given frequency range, the presence of six families of circumferential waves labeled lw (1≤lw≤6) was noted. The resonances of these families, except lw=1, are wide compared to those of aluminum or steel cylinders. Nevertheless, the resonances of the first family are easily detected in the Lucite cylinder, contrary to aluminum or steel cylinders. The scattering of a plane‐wave pulse can be represented by the Fourier integral in order to determine a theoretical resonance spectrum without choosing the background. A good agreement is obtained for the studied frequency range between experimental and theoretical results. ...

The aim of this work is to study theoretically and experimentally, the acoustic radiation of a cylindrical elastic shell excited by a point source with no internal loading and immersed in a water tank. We are primarily focused on the theoretical study of a cylindrical elastic shell receiving a point force in the form of a Dirac pulse and the acoustic pressure radiated along the tube into a point at far-field observation. The model used is based on the theory of elasticity. It is therefore interesting, in a second step, to conduct experiments to validate these theoretical calculations and to realize complementary measures corresponding to the case of a focalized observer. The used shell is a cylindrical stainless steel tube characterized by its ratio equal to 0.94. Two experiments are carried out. The first experiment is based on a bistatic method, and the transmission and reception are performed by two focalized transducers, characterized by a center frequency of 1 MHz. For the second experiment, the two ...

A marine current turbine is made of a boss and several blades. An acoustic scattering method is appropriate to detect defects in this machine. The acoustic backscattering from a blade identical to a finite plane plate has previously been studied. The flight times of acoustic echoes are calculated taking into account the quasi Lamb waves in a plate. In order to connect with the reality, the shape of the chosen blade is a bent finite dimension sheet. To simplify the study, a half cylindrical shell obtained cutting a tube in two parts is used. This target, immersed in water, is excited with short impulses in a plan perpendicular to its surface with incidence angles between 0 to 360°. Successively, the convex part and the concave part of the half tube are excited. The backscattering signals are compared with those which are obtained from an air-filled cylindrical shell immersed in water. The flight times of the different acoustic signals are identified taking into account the circumferential guided waves in the shell. Spectra are computed with a Fourier transform and the resonances are identified. The convex part and the concave part do not give same results. This experimental result will be explained.

The assessment of sound pressure levels generated by submerged structures is part of problems regarding underwater noise pollution. The growing number of offshore constructions related to energy generation by wind farms increases the importance of these studies. The understanding of physical mechanisms responsible for this radiation should allow us to reduce the noise by refining the construction of structures. The object of the present work is the study of underwater acoustic radiation of tube vibrations. The results presented were obtained on two stainless steel tubes. These tubes are placed vertically into water. The vibrations are generated by a shock obtained using a hammer with a force sensor hitting the tube on the emerged part. The vibrations of the tube placed in the air and in water are measured using accelerometers. The influence of water on the modes of resonances observed is then highlighted. The acoustic radiation measurements are made by a hydrophone located at a few meter distance of the tube. Results are presented as time signals and spectra and are compared to results of analytical and numerical calculations. Relationships between the resonances of the tube and the acoustic radiation in water are then interpreted.

This paper is devoted to the study of acoustic vibrations induced by a flow upon an air-filled cylindrical tube vertically placed in water. A water pump with adapted piping generates a turbulent flow horizontally canalized in a large laboratory tank (6 m × 4 m × 3 m). The tube is located across this flow and an accelerometer measures vibrations. The signal processing performed on the recorded signals brings out resonance modes of the tube excited by the flow. A theoretical study (tube in air) and complementary experiments (tube in air and in water) are conducted to identify these modes.

International audience; This paper revisits the vanishing of the transverse component of the particle displacement vector in free surfaces of an isotropic homogeneous plate, for both symmetric and antisymmetric Lamb waves. Drawing on well-known analytical expressions from Viktorov’s book [(1967) Rayleigh and Lamb Waves: Physical Theory Applications, Chap. II, pp. 67–121], two distinct frequency-thickness product expressions, in cases where this vanishing occurs, are derived: one for the symmetric modes and another for the antisymmetric modes. At these frequency-thickness products, phase and group velocities have appreciable values which are discussed herein. It appears that these velocities depend on the transverse bulk wave velocity only. This is the specific condition of the Lamé modes. Moreover, theoretical and experimental investigations of displacements in the surface of a plate in air have been carried out. The theoretical part shows that the normal and transverse displacements have, respectively, a local maximum and a local minimum in the vicinity of these frequency-thickness products. The experimental part corroborates the presence of the local maximum of the S0 Lamb mode for various materials.

In this paper, the interaction of the longitudinal mode L(0,4) with a resin deposit coupled to the wall of a stainless steel pipe is studied. The considered deposit has the shape of an axisymmetric ring. The purpose of this work is to analyze the attenuation of mode L(0,4) as a function of deposit width. A finite element model is used for the computation of displacements at the pipe surface and a bistatic measurement method is employed to obtain time signals related to displacements at the same surface. A good agreement between the numerical predictions and the experimental results allows us to discuss the attenuation of mode L(0,4). An exponential law of the attenuation versus the deposit width is deduced from various results. To show that this loss of energy is mainly due to the scattering of mode L(0,4) in the deposit during its propagation along the pipe, an additional study on the scattering of mode L(0,4) is carried out for a stainless steel pipe embedded in a resin matrix.

Acoustic scattering from an isotropic elastic hollow cylindrical shell of infinite length excited by an obliquely incident plane acoustic wave is investigated. The form functions of an aluminum cylindrical shell immersed in water have been calculated by the direct summation of the Rayleigh series. Computations are made at angles (with the normal to the cylinder axis) between α=0° and α=35°. The results of the theoretical calculation are in good agreement with the results of experiments. The experimental results have shown in a frequency range of k1a=0 –20 that the resonances are related to three wave families: the circumferential wave (l=2) detected for angles smaller than the ‘‘angle of longitudinal wave in thin rods’’ (αl), the guided wave (p=1) detected for angles smaller than the second critical angle (αT), and the Scholte–Stoneley wave (l=0). The evolution of the resonance frequencies is followed for different angles and one can note experimentally, that at an angle superior to the Rayleigh critical ...

This paper presents theoretical and experimental studies of axisymmetric longitudinal guided wave L(0,2) interaction with the free edge of the pipe. A numerical method based on normal mode superposition is applied to predict the edge resonance by an analysis of dispersion relations of separate modes. In parallel, the finite element analysis and experimental measurements prove the existence of edge resonance in the pipe in case of L(0,2) wave incidence. It is shown that the edge resonance is mainly caused by the first pair of complex modes. Additionally the behavior of edge resonance phenomenon as a function of the curvature of the pipe is studied. The displacement amplitudes measured at the edge demonstrate that the edge resonance is affected by the frequency and thickness to midradius ratio of the pipe, and it is losing its strength in thicker pipes, as the growing difference between the outer and inner radii destroys symmetry. The reflected energy amplitudes show that at the resonance frequencies the incident wave is strongly converted to L(0,1) and L(0,3) modes, depending also on the curvature parameter of the pipe.

Our interest is taken in the reflection and the attenuation of longitudinal waves caused by a circular shape deposit placed on the pipe wall. The reflection of the S0 mode by the deposit is experimentally shown. The experimental results are compared with the theoretical results obtained from a finite element method (FEM). The attenuation of modes is determined and analyzed for five widths of deposit. In the case of a tube filled with water, only the symmetrical waves, S0 in low frequency and S1 (f=2.56 MHz), are considered because of their strongly axial nature. A viscous deposit (epoxydic resin) characterized by different widths and placed on the surface of a pipe is the defect considered in this article. Our interest is taken in the attenuation of the longitudinal waves at particular frequencies. Theoretically and experimentally, the propagation of guided waves is considered in a stainless steel tube (length L=3 m) with an outer radius a = 19 mm, an inner radius b = 17.5 mm (thickness d = 1.5 mm). The mechanical parameters are CL = 5823 m/s (longitudinal wave speed), CT = 3210 m/s (transverse wave speed), ρ = 8027kg/m 3 (density), filled or not with water (Fig.1).

Acoustic scattering from an isotropic elastic hollow cylindrical shell of infinite length excited by an obliquely incident plane acoustic wave is investigated. Firstly, a Method of Isolation and Identification of Resonances called MIIR in «propagation» enables us to observe the propagation of waves (in a direction parallel to the cylinder axis) like the guided waves p=2 and p=1. An isolation and an identification are possible in an important range of incidence, contrary to a configuration of two transducers according to Snell-Descartes' law. Secondly, the nature of these waves is analysed with the axial displacement. The choice of this displacemement is confirmed by the angular diagram of the pressure radiated by the circular section, at the end of the tube

The non‐destructive evaluation of pipes using guided waves is extensively used for the detection and the size estimation of defects. The important number of investigations concerning with the interaction between a guided wave and a defect show the growing need to improve our knowledge of this phenomenon in order to detect and to characterize as well as possible the defect. This work is devoted to the evaluation of the width of an axisymmetric resin deposit coupled to the wall of a metallic tube by means of longitudinal modes S0, S1. To that end, we interest to damping of these modes provoked by the deposit. The study is carried out both from the numerical point of view and from the experimental point of view in considering a deposit of variable width. The finite element method is employed to model the propagation and the diffraction of Lamb‐type waves. The experiment is based on the generation of axisymmetric waves on the section of a tube by a piezoelectric transducer. Measurements of temporal echoes ref...

Considerable work has been done on the scattering by cylindrical objects having a circular cross section. The modal formalism based on the theory of elasticity has been developed for studying the acoustic scattering by these elastic cylinders immersed in water. In particular, it has been demonstrated, in normal incidence, that the eigenfrequencies of a circular cylinder can be determined from a resonance spectrum. These eigenfrequencies correspond to circumferential waves that form a resonance when a phase matching along a closed path is obtained. Each eigenfrequency is characterized by a given mode n, i.e., the number of wavelengths spanning the circumference. Comparatively, little attention has been devoted to the more general case of the noncircular cylindrical cylinders such as the elliptical elastic cylinders. For these objects, we have been developed a modal formalism based on the theory of elasticity. From the results obtained theoretically and experimentally, we show how to obtain a resonance spectrum, independently of the azimuth incident angle and of the radii ratio (minor radius and major radius) so that the eigenfrequencies can be determined. We present also a modal analysis of resonances as function of the azimuth incident angle and of the radii ratio.

Acoustic scattering from a finite air-filled elastic cylindrical shell, immersed in water, is investigated. The shell is made of stainless steel and has a thickness to outer radius ratio of 17%. The considered dimensionless frequency range extends over 7k1a22 (k1: wave number in water, a: outer radius). Bistatic measurements are carried out to identify vibration modes related to the phase matching of the first guided wave, T0, propagating on the shell. Both transducers, the emitter and the receiver, are positioned at the same angular distance with regard to the normal axis of the shell. The emitter transducer is fixed at a given position. In order to identify circumferential modes of vibration, the receiver transducer is made to rotate in the azimuthal plane, normal to the shell axis. Results obtained are plotted in functions of dimensionless frequency and azimuthal angle. Vibration modes along the shell's length are identified by moving the receiver transducer parallel to the shell axis. In this case, results are plotted in functions of dimensionless frequency and axial wave number. The experimental investigation is corroborated by theoretical results obtained from approximate calculations for thick finite cylindrical shells [Scot F. Morse et al., J. Acoust. Soc. Am. 103, 785-794 (1998)]. The evolution of the mode position with respect to the incidence angle is discussed so as to clarify peak patterns in backscattered resonance spectra.

The real parts of the eigenfrequencies of an evacuated, fluid‐immersed infinite cylindrical shell can be used to obtain the dispersion curves versus frequency of the phase velocities of families of circumferential waves. These waves are analogous to those of the families of Lamb waves on an elastic plate in vacuo, but contain an additional A wave corresponding to the Scholte–Stoneley wave in the fluid loading [see M. Talmant, Ph.D. thesis, Univ. of Paris VII (1987), or M. Talmant et al., J. Acoust. Soc. Am. 86, 278 (1989)], which is approximated by the first Franz wave [B. Clotteau et al., J. Acoust. 3, 213 (1990)]. Near the coincidence frequency, a repulsion phenomenon is obtained between the (Lamb wave) A0 and the A‐wave dispersion curves, analogous to that in perturbed, quasidegenerate atomic levels. An analytic explanation is provided, using perturbation theory, for the form of the dispersion curves and the nature of the corresponding waves in the region of repulsion.

Acoustic scattering from an isotropic elastic hollow cylindrical shell of infinite length excited by an obliquely incident plane acoustic wave is investigated. The waves generated at an incident angle α on a determined area of a cylindrical shell immersed in water and filled with air, propagate in a direction parallel to the cylinder axis and re‐emit their energy during the propagation at an angle α. The various velocities of propagation of helical waves allows one to record separately the resonance spectrum of each type of waves. Then, the radiation, in the far field, can be observed for each wave, at the end of a shell of semi‐infinite length, with a quasiharmonic method. In this case, no phenomenon of stationary waves can occur in the cylinder length. The axial displacement is analyzed and the use of the Rayleigh integral allows one to determine a model of the pressure radiated by the circular section of the tube. The results of the theoretical calculation are in agreement with the results of experiments.

Acoustic scattering from a Lucite cylinder of infinite length immersed in water and excited by a normal incident plane acoustic wave is investigated at low frequencies. Numerical calculations and experiments are performed for a cylinder with a radius a=0.01 m. The experimental results are obtained with the method MIIR. The resonances of the first circumferential wave are easily isolated in the frequency range 100–300 kHz. A good agreement is obtained between experimental and theoretical results. First, in order to analyze the physical nature of vibration modes associated with this wave, the evolution of the resonance location and that of their corresponding widths are investigated theoretically when the fluid density is perturbated. Contrary to aluminum or steel cylinders, the computed calculus in vacuum are not in good agreement with the experimental results related to the first wave. The detection of this wave depends mainly on the outer fluid. Second, the dispersion curves of the phase velocity for thi...

The theoretical and experimental spectra, obtained from an infinite pipe insonified with a plane wave in oblique incidence, show resonances which are related to three types of helical waves: the circumferential waves (Ai or Si waves), the transversal guided waves (Ti waves), and the Scholte wave (A wave). The resonances of the Scholte wave are detected in a frequency window and their frequency slowly increases when the incidence angle increases, whereas the ones of the other waves increase towards infinity when the incidence angle tends towards the transversal critical angle. At oblique incidence, the experimental results obtained with the MIIR show resonances which are related to the helical waves S0, T0, T1, and A. This method uses a long pulse with many sinusoid periods, a steady state takes place in a part of the infinite shell. In this presentation, the excitation is a short pulse and the scattered echoes are detected when the helical wave emission is in front of the receiver. Between each echo, the ...

The fluid‐borne interface wave on an evacuated cylindrical shell immersed in water is known as Scholte–Stoneley wave, or also as A wave [Talmant et al., J. Acoust. Soc. Am. 86, 278 (1989)]. The resonances of this wave, caused by phase matching upon its multiple circumnavigations of the scattering object, can be observed in the backscattering spectra of incident sound waves within a frequency window that depends on the shell thickness, for thicknesses less than 40% of the cylinder radius. The interaction between the flexural wave A0 in the shell, and the Scholte wave is studied in detail as a function of shell thickness. Dispersion curves for the A and the A0 waves are presented, indicating a region of repulsion between these two curves corresponding to a change of the physical nature of the two waves.

The observation of the guided waves p=1 and p=2 from an isotropic elastic hollow cylindrical shell of infinite length excited by an obliquely incident plane acoustic wave is investigated. The use of ‘‘classic’’ MIIR (method of isolation and identification of resonances) is limited because of the refraction effect of the surface wave: The state of stationarity generated at a resonance frequency occurs out of the insonified area of the cylindrical shell. This problem has been solved by a new method called MIIR ‘‘in propagation.’’ Then, an isolation and an identification are possible in a large range of incidence, contrary to the configuration of transducers according to Snell–Descartes’ law (‘‘classic’’ MIIR). The resonances of the guided wave p=1 can be detected in a broad range of incidence angle. Contrary to the guided wave p=1, the experimental results achieved with incidence angles varying between 0° and the second critical angle show a particular evolution of the resonance frequencies of the guided wa...

The acoustic scattering from infinite cylinders or spheres has shown the great influence of surface wave propagation. Two types of surface waves are distinguished: the Rayleigh or Whispering Gallery waves and the Scholte–Stoneley waves. In this study, experimental results obtained on the finite cylindrical shells bounded by two hemispherical endcaps are presented. These objects are made of stainless steel and filled with air. Their radius is 27 mm and their radius ratio b/a is 0.97 (b is the inner radius and a the outer radius). The direction of insonification is parallel to the main object axis. The reduced frequency range k1a of the study varies from 10 to 40. These experimental results are explained by writing the stationary condition on the large circumference of objects, in the meridian plane. This condition depends on the phase velocity in the length of the cylindrical shell and in the spherical shell. These two velocities are computed separately in relation to the frequency and used to apply the st...

Forward acoustic scattering for solid spherical and LINE (limited cylinder bounded by hemispherical endcaps) objects immersed in water in bistatic configuration is the topic of this study. First, bistatic configuration analysis is carried out for a spherical object whose analytical theory has already been developped. Experimental and theoretical angular diagrams show, for differents frequencies, a peak of strong amplitude located in the shadow area. After the temporal analysis for a solid sphere in the shadow area, two important echoes revealing at least two different kind of waves are isolated. Then, the waves mainly responsible for these echoes are then identified comparing experimental results and theretical calculations. These are the Franz wave F0 and the whispering gallery wave l=2. Their propagation velocities on the object are calculated experimentally. Considering a solid LINE excited axially, on its spherical part, it is interesting to note that the physical mechanisms responsible for the wave generation are the same than for a solid sphere. It is then possible to find for a axially excited solid LINE the same kind of waves than for a solid sphere. Others waves are then identified (mainly caused by parasite difraction and by the cylinder/hemispherical discontinuity of the LINE). At last, the caracterization of the LINE as an acoustic target by the mean of a numerical simulation is performed, first with the target strenght standard, and then with the Rsn criterion. This last number allow us to assess the resonating contributions of the object and then to establish a map of resonance contributions.; L’étude de la diffusion acoustique pour des objets sphériques et de forme LINE (cylindre terminé à chacune de ses extrémités par une calotte hémisphérique) pleins et immergés dans l’eau en configuration bistatique est l’objet de ce mémoire. Une attention particulière est portée à la diffusion vers l’avant par ces objets. L’analyse en configuration bistatique est effectuée dans un premier temps pour un objet sphérique pour lequel une théorie analytique a déjà été développée. Les tracés des diagrammes angulaires expérimentaux et théoriques (à plusieurs fréquences données) montrent l’existence d’un lobe de forte amplitude localisé en zone d’ombre. Une analyse temporelle est menée, pour la sphère pleine, précisément dans la zone d’ombre où deux échos majeurs, révélateurs d’au moins deux types d’ondes, sont isolés. Les ondes principalement responsables de ces échos sont ensuite identifiées, en comparant les résultats expérimentaux obtenus et les calculs théoriques, comme étant d’une part une onde de Franz F0, et d’autre part une onde de Galerie à échos l=2. Leurs vitesses de propagation sur le solide sont calculées par le biais des seules données expérimentales. En considérant une LINE pleine excitée axialement, sur sa partie sphérique, il est intéressant de noter que les mécanismes physiques à l’origine de la génération des ondes sont les mêmes que pour une sphère pleine. Il est donc possible de retrouver dans le cas de la LINE pleine excitée axialement les mêmes types d’ondes se propageant que pour la sphère pleine. D’autres ondes sont ensuite identifiées (principalement dues à des réflexions parasites et à la discontinuité cylindre/hémisphère de la LINE). Enfin, la caractérisation de la LINE à l’aide d’un modèle numérique en tant que cible acoustique est effectuée, d’une part avec le critère d’index de cible, et d’autre part avec un critère Rsn. Ce dernier critère nous permet notamment de mesurer les contributions résonantes de l’objet et d’établir une cartographie des contributions résonantes.