Lens mediated scattering of sound by sound with finite aperture beams.

An experimental concept for measuring sound-sound scattering of finite aperture acoustic beams in a water tank facility is presented. In order to achieve a measurable effect, the beams are collimated within their intersection domain by a focusing acoustic lens. A paraxial quasi-linear split step simulation tool has been developed and used in order to determine and optimize experiment setup parameters. The scattered part of the difference frequency field was measured and found to be compatible with simulations. Furthermore, the primary beams were also monitored in order to guarantee full compatibility with simulated propagation and compare the measured difference field with the overlap contribution. A spatially coherent post processing filtering was applied in order to improve the signal to noise ratio. A distinct clear scattering peak in the difference field has been identified propagating with the predicted off axis tilt angle.