A modal attenuator for reducing noise in a process system having fluid flowing through a pipe, the modal attenuator comprising: an inlet for in-line connection to a first pipe; an outlet for in-line connection to a second pipe; an attenuator body extending along a length from the inlet to the outlet and defining a primary fluid flow path from the inlet to the outlet; characterized in that the modal attenuator further comprises: a perforated screen disposed inside the attenuator body, the perforated screen having a cylindrical screen body surrounding the primary fluid flow path from the inlet to the outlet; a plurality of annular walls extending inwardly from the attenuator body such that the plurality of annular walls are disposed on an inside surface of the attenuator body; and a plurality of chambers spaced along the length of the attenuator body, the chambers defined by the plurality of annular walls and between the attenuator body and the perforated screen, wherein each chamber has a width , a height , and an open end facing the perforated screen such that acoustic waves passing through the perforated screen can enter into the chamber through the open end; and wherein the heights of the chambers alternate along the length of the attenuator body between a larger height chamber and a smaller height chamber. an inlet for in-line connection to a first pipe; an outlet for in-line connection to a second pipe; an attenuator body extending along a length from the inlet to the outlet and defining a primary fluid flow path from the inlet to the outlet; characterized in that the modal attenuator further comprises: a perforated screen disposed inside the attenuator body, the perforated screen having a cylindrical screen body surrounding the primary fluid flow path from the inlet to the outlet; a plurality of annular walls extending inwardly from the attenuator body such that the plurality of annular walls are disposed on an inside surface of the attenuator body; and a plurality of chambers spaced along the length of the attenuator body, the chambers defined by the plurality of annular walls and between the attenuator body and the perforated screen, wherein each chamber has a width , a height , and an open end facing the perforated screen such that acoustic waves passing through the perforated screen can enter into the chamber through the open end; and a perforated screen disposed inside the attenuator body, the perforated screen having a cylindrical screen body surrounding the primary fluid flow path from the inlet to the outlet; a plurality of annular walls extending inwardly from the attenuator body such that the plurality of annular walls are disposed on an inside surface of the attenuator body; and a plurality of chambers spaced along the length of the attenuator body, the chambers defined by the plurality of annular walls and between the attenuator body and the perforated screen, wherein each chamber has a width , a height , and an open end facing the perforated screen such that acoustic waves passing through the perforated screen can enter into the chamber through the open end; and wherein the heights of the chambers alternate along the length of the attenuator body between a larger height chamber and a smaller height chamber. <EOS>