Numerical simulation of impact sound transmission control across a smart hybrid double floor system equipped with a genetically-optimized NES absorber

Abstract

An idealized detailed 2D formulation is presented for suppression of transient impact sound transmission across a hybrid smart double-leaf sandwich beam (floor-ceiling) structure into a rectangular (receiving) room with ideally flat and rigid walls. The smart double wall structure, which is mechanically inter-connected at an arbitrary point with a lightweight nonlinear energy sink (NES) absorber, incorporates spatially distributed and electrically independent non-collocated semiactive (electro-rheological fluid- or ERF-incorporated) and fully-active (piezoceramic- or PZT-incorporated) actuator layers functioning in a closed loop control framework. Extensive time-domain numerical simulations initially calculate both the uncontrolled and controlled transient acoustic pressure fields in absence of the dynamic vibration absorber for four separate settings of the active (PZT-) and semiactive (ERF-) actuation elements. Subsequently, the remarkable performance of the GA-optimized hybrid smart active/semi-active/passive (PZT/ERF/NES) configuration, which benefits from the multi-mode targeted energy transfer (TET) mechanism of the NES, in significant broadband (low frequency) attenuation of the transmitted shock energy with a much lower actuator energy demand, is demonstrated. Furthermore, some important aspects of the transient fluid-structure interaction (TFSI) control problem like weakening of the acoustic shock focusing effects (focal zones) within the source room are illustrated through selected early-to-late-times 2D images and animations of the cavity pressure fields. Limiting situations are studied and correctness of the derivations is established against accessible data in addition to numerical (FEM) simulations.