Layout optimization and mechanism analysis of hybrid active and passive micro-perforated panel absorber for suppressing enclosed sound field

This paper investigates the sound absorption performance of hybrid active and passive micro-perforated panel absorber (MPPA) for suppressing the enclosed sound field. The hybrid MPPA is strongly coupled with the enclosed sound field so that it serves as a sound energy dissipating component, rather than a uniform absorption boundary. The in situ sound absorption is highly dependent on its layout on the boundary of the enclosed space, which is worth exploring in depth for aiding in its practical application. The fully coupled enclosure-hybrid MPPA model is established using modal analysis approach. The evolution mechanism of passive and active sound absorption performance in various layout situations are explored both for rectangular and irregular enclosed space, thus providing guidance for layout optimization. Simulations show that the energy dissipation of partial MPPA coverage with appropriate layout is better than the full coverage case. The dissipation when partial covered MPPA locating at the corner is more significant than that at the middle position for rectangular enclosed space. The weakened coupling effects between the enclosure and the MPPA cavity mainly result in the significant dissipation on resonances of the coupled system. Since the irregular cavity modes significantly weaken the above coupling effects, the dissipation of full coverage case is the best for irregular enclosure. Applying active control to suppress the sound field of the MPPA cavity can generate pressure difference across the MPP, which dissipates energy of the undamped resonances of the coupled system to a minimum until a new equilibrium state is reached. The pressure release strategy is applicable both for full and partial coverage cases. The partial covered MPPA needs to be located in the corner to guarantee the control performance of such strategy, meaning that active control requires the cooperation of passive control to achieve better performance.