Acoustic silencing in a flow duct with micro-perforated panel liners

Despite the increasing interest in Micro-perforated panels (MPPs) for various noise control applications, the acoustic behavior of MPP liners in flow ducts has not been fully apprehended. On the top of this is the lack of understanding on the influence of various design arrangements and system parameters on the performance of MPP-based acoustic silencing devices. Incorporating previously developed acoustic impedance formulae within the general framework of the Patch Transfer Function (PTF) framework, these issues are investigated in this paper in the context of a MPP liner, flush-mounted inside a flow duct wall. Numerical analyses reveal the effects of the grazing flow and different partition arrangements in the backing cavity of MPP liners on their silencing performance as well as the underlying physical phenomena. Capitalizing on the efficiency of the modelling approach, a system optimization is carried out. The numerically predicted noise attenuation results are validated through comparisons with experimental measurements under various grazing flow velocities. While shedding light on the underlying sound attenuation mechanism, studies provide guidelines for the design of MPP silencers in flow ducts.