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Quelques effets du désordre et des non-linéarités sur la propagation des ondes sonores

Abstract : In the first part of this thesis we study the acoustics of foams. Our experimental results show that both sound velocity and absorption vary with foam aging, due to the evolution of its structure. To explain the sound speed evolution we show that one must consider the liquid-matrix elasticity. We also show that sound attenuation is very high and that it is dominated by thermal dissipation at the gas-liquid interfaces. In the second part, we compare the contribution of acoustic nonlinearities induced by moving boundaries with respect to those induced by volume effects. Then we study the scattering of a sound wave by a plane oscillating surface and we characterize two regimes: the spectrum of the scattered wave is principally induced by either the Doppler effect at the moving boundary or by volume acoustic nonlinearities. In addition, we show that it is possible to use the Doppler shift in the scattered wave to measure precisely the amplitude oscillation of the scatterer. The last part of this work consists in a study of the volume acoustic nonlinearities near the critical point (CP) of CO2. We show that they increase near the CP with two different experimental techniques: the nonlinear resonance of an acoustic cavity mode and the nonlinear interaction of two high frequency waves. Finally, we present an experimental study of scattering of sound by sound under a non-zero angle. This works permits us to conclude that the nonlinear acoustic parameter increases by a factor of 100 near the CP of CO2.
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https://tel.archives-ouvertes.fr/tel-00002000
Contributor : Nicolás Mujica Fernandez <>
Submitted on : Friday, November 22, 2002 - 12:57:29 AM
Last modification on : Thursday, December 10, 2020 - 12:38:59 PM
Long-term archiving on: : Friday, April 2, 2010 - 6:37:06 PM

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  • HAL Id : tel-00002000, version 1

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Nicolás Mujica Fernandez. Quelques effets du désordre et des non-linéarités sur la propagation des ondes sonores. Physique [physics]. Université Pierre et Marie Curie - Paris VI, 2002. Français. ⟨tel-00002000⟩

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