A fan casing for a gas turbine engine is provided which combines the functions of blade containment and noise suppression. The fan casing has an annular metallic inner shell with a plurality of holes are formed therethrough. An acoustic absorber, such as a cellular resonator, is disposed around the inner...http://www.google.com/patents/US6619913?utm_source=gb-gplus-sharePatent US6619913 - Fan casing acoustic treatment
