On the realization of acoustic attenuation using a microperforated panel alone

An attempt is made to achieve acoustic attenuation using a microperforated panel (MPP) without the commonly used backing air cavity. The underlying mechanism is the generation of the air motion inside the micropores as a result of the acoustic pressure difference on the two sides of the MPP. The acoustic environment in which such a mechanism is viable is found in a curved duct where the axial wavenumber below the cut-off frequency of the first dispersive mode is radius dependent. A MPP inserted into this duct results in an acoustic pressure difference on its two sides associated with the two sub-curved duct domains and enables the vibration of the air inside the micropores. Results show that energy is absorbed by the MPP and the effect extends over a broad frequency band and down to very low frequency.