An acoustic structure for reducing noise generated from a source, said acoustic structure comprising: a honeycomb comprising a first edge to be located closest to said source and a second edge, said honeycomb comprising a plurality of walls that extend between said first and second edges (15,17), said walls defining a plurality of cells wherein each of said cells has a cross-sectional area measured perpendicular to said walls; an acoustic barrier located at the second edge of said honeycomb or within at least one of said cells to form an acoustic resonator wherein the depth of said acoustic resonator is equal to the distance between the first edge of said honeycomb and said acoustic barrier; a sound wave guide located in said acoustic resonator, said sound wave guide comprising an acoustic guide wall having interior and exterior surfaces (34,36), said acoustic guide wall comprising an inlet edge defining a wave guide inlet and outlet edge defining a wave guide outlet wherein said wave guide inlet is closer to said honeycomb first edge than said wave guide outlet and wherein said acoustic guide wall divides said honeycomb cell into an inner sound wave channel defined by the interior surface of said acoustic guide wall, said wave guide inlet, said wave guide outlet and the portion of said cell wall that extends between said wave guide inlet and the first edge of said honeycomb and an outer sound wave chamber defined by the exterior surface of said acoustic guide wall, said acoustic barrier, said wave guide outlet and said honeycomb wall; characterized in that said acoustic guide wall is made from a perforated material or a mesh fabric. a honeycomb comprising a first edge to be located closest to said source and a second edge, said honeycomb comprising a plurality of walls that extend between said first and second edges (15,17), said walls defining a plurality of cells wherein each of said cells has a cross-sectional area measured perpendicular to said walls; an acoustic barrier located at the second edge of said honeycomb or within at least one of said cells to form an acoustic resonator wherein the depth of said acoustic resonator is equal to the distance between the first edge of said honeycomb and said acoustic barrier; a sound wave guide located in said acoustic resonator, said sound wave guide comprising an acoustic guide wall having interior and exterior surfaces (34,36), said acoustic guide wall comprising an inlet edge defining a wave guide inlet and outlet edge defining a wave guide outlet wherein said wave guide inlet is closer to said honeycomb first edge than said wave guide outlet and wherein said acoustic guide wall divides said honeycomb cell into an inner sound wave channel defined by the interior surface of said acoustic guide wall, said wave guide inlet, said wave guide outlet and the portion of said cell wall that extends between said wave guide inlet and the first edge of said honeycomb and an outer sound wave chamber defined by the exterior surface of said acoustic guide wall, said acoustic barrier, said wave guide outlet and said honeycomb wall; characterized in that said acoustic guide wall is made from a perforated material or a mesh fabric.