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Figure 4: (a) Experimental realization of the symmetric metasurface cloak made out of two jointed semishells (radius 40 cm): (a) lossy Helmholtz resonator array and active loudspeakers controlled by gain circuits. (b) Full-wave simulations of the pressure field of a bare rigid cylinder when insonified from the left by a plane wave at f = 3 kHz. The dashed test areas have been experimentally measured. (c) Simulations of the metasurface cloak surrounding the rigid obstacle and the corresponding measurements at the front and the backside of the decorated obstacle.