Layered chamber acoustic attenuation

An acoustic attenuation device comprising resonator panels stacked in a thickness direction of the device, wherein each resonator panel is tuned to a different frequency range and includes a plurality of openings through which excited air resonates, the resonator panels being placed adjacent to other resonator panels such that all openings are accessible to the environment, wherein the device extends from a first end to a second end thereof and each resonator panel comprises:

• first and second sheets;
• a plurality of webs positioned between the first and second sheets and cooperating with the first and second sheets to form a series of sound attenuation chambers containing a volume and mass of fluid;
• a first end sheet secured to the sheets and closing the chambers at the first end of the device;
• a second end sheet secured to the sheets and closing the chambers at the second end of the device;
• and
• first and second openings of the plurality of openings associated with each chamber and through which excited air resonates, the first and second openings extending through the first sheet into each chamber, each first opening having an invariable cross-section and at least one of the second openings having an adjustable cross-section for varying a resonant frequency of the chamber.