A parallel-plate acoustic waveguide supporting ten modes at the working frequency. It contains cylindrical rigid scatterers (in black). The bottom surface of this waveguide is formed by the water in this container, so that the spherical object (orange ball) can float and move freely. Wave-momentum shaping consists of finding and sending, at each time t m , the optimal mode mixture to push the ball along an arbitrarily chosen path (orange line). We achieve this by real-time far-field measurements, which allow us to track the evolution of the scattering matrix S as the object moves. We deduce the wavefronts to be injected by the external speaker arrays such that they optimally deliver the target momentum.
