Attenuating open cavity tones by lining its walls with microperforated panels

Open cavities subjected to a grazing air flow produce high level aeroacoustic noise consisting of intense discrete and broadband components. The discrete components are generated when the air flow induces acoustic waves that drive the resonance modes of the cavity. The acoustic resonances in the open cavity can be reduced by noise control techniques. One passive control technique consists of lining the inner walls of the cavity with absorbing material. While porous materials provide wideband absorption, they are discouraged in presence of air flow. Microperforated panels (MPP) have been proposed as the next generation absorbers that can be used in presence of air flow. Furthermore, their usually high manufacturing cost can be drastically reduced by an infiltration technique. This paper reports the reduction of resonance tones when an open cavity is lined with MPPs fabricated by infiltration.