From MPA to strategically designed absorbers using solid freeform fabrication techniques

This paper reports on current work investigating the development of an alternative single material, broad frequency acoustic resonator by applying geometric changes to the cavity, without using sub-millimetre features. The inclusion of internal features such as fins and perforated layers are considered. The manufacture of these complex components is possible directly from CAD data via relatively new manufacturing techniques collectively know as Rapid Manufacturing. The technology has limitations for this application which are explored in the paper. Significant resistance however, has been achieved without the use of resistive materials or sub-millimeter features and significant improvements in peak absorption and increases in bandwidth over ¾ of an octave have been attained. These findings are currently being utilised in the development of a broad frequency absorber.