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The study of acoustic propagation of a transmitted wave in bubbly water shows a very strong attenuation of this wave around the monopole resonance in low frequency of the bubbles. This is due to the multiple scattering between the bubbles. If the bubble concentration is high enough, the bubbly medium acts as a stopband by reducing completely the transmitted wave amplitude. The interest of the present paper is experimentally to bring out additional attenuation bands in high frequency. In a water-filled tank, two transducers are located opposite one another. Microbubbles are injected perpendicular to the axis of transducers, with a high pressure water jet. To obtain the attenuation, the impulse response of the bubbly water is measured in 0.03-10 MHz frequency range, with different characteristics of transducers. The additional stopbands are obtained and a theoretical study of their relation with the bubble sizes and the bubble concentration is initiated and discussed.

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.