Acoustic Absorption of a Microperforated Panel Without the Backing Cavity

This paper contributes to exploring the use of a microperfroated panel (MPP) in an unconventional way. Over the years, MPPs have been extensively used for a variety of acoustics problems. In all those applications, MPPs are often accompanied by the backing air cavity so that they constitute a resonance system which leads to an effective acoustic absorption around its resonance frequency. Subsequent work are often seen in terms of MPP parameters optimization, backing cavity design and the incorporation of active components into the absorber, which remains in the framework of cavity-backed MPP absorber system. In this paper, it is demonstrated that a MPP can be used independently for acoustic absorption without the commonly used backing cavity. To allow this mechanism to be effective, a MPP should be placed in an environment in which an acoustic pressure difference occurs between the two sides of the MPP. Such an environment is found in a curved duct where the axial wavenumber is radius dependent. A MPP insertion separating the bend into two curved subdomains is then able to realize acoustic absorption without the need for a backing cavity. This is evidenced by both simulation and experiment.