While for most effective aircraft sound sources noise reduction concepts can be demonstrated, high lift noise represents an essentially unsolved problem. Knowledge acquired in the first funding period indicated that the use of permeable materials with spatially varying anisotropic properties (graded materials) could reduce airframe noise considerably. The objective of the second funding period is to explore their noise reduction potential by means of numerical simulation and acoustic wind tunnel tests. Porosity models in the perturbation equations will be extended and validated to represent anisotropy and graded properties. Of particular interest is the understanding of the sound generation as well as the demonstration of a silent Coanda flap system, which for a given aerodynamic performance is considerably more silent (5-10dB) than a conventional high lift system.