As a continuation of previous experiments we present results from a model experimenf on reflection and refraction of a narrow sound beam at an oil-water interface, with critical incidence angle near 62 degrees. The incident, reflected and refracted sound field were recorded for incidence angles between 52 and 73 degrees. The sound source was a parametric array yielding a 250 kHz beam of 3-dB width equal to 5 wavelengths at the interface located 5 array lengths from the primary source. The results clearly show interference between the reflected beam and the lateral wave, between the evanescent wave and the refracted wave, and between the incoming and reflected wave, as a function of incidence angle. Beam displacements are found to be both towards and away from the primary source depending on incidence angle, for both the reflected and the refracted beam. The angle of the reflected beam is larger than the incidence angle when the latter is near the critical incidence angle. The shape of the reflected beam becomes markedly asymmetric for incidence angles above the critical, and the interference with the lateral wave is seen as fluctuations on the under-side of the beam.
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