Helmholtz Resonator Liner with Flexible Walls

Abstract

In this experimental investigation, a novel liner concept (FlexiS) has been introduced and tested. An increased overall damping performance and an increased frequency range of significant damping mainly at lower frequencies could be obtained by replacing some of the rigid walls of an SDOF liner by exible materials with inherent damping. The concepts proved its benefits if some non-active parts (i.e. no direct connection to the grazing sound field) were placed between the active cells. Measurements of the dissipated acoustic energy of the whole liner and of the acoustic pressure inside neighboring cells reveal the importance of the exible walls. In the current investigation, the arrangement of active (open) and non-active (taped) cells allowed for a great exibility in liner setup without comprehensive changes or re-manufacturing of the liner. However, in terms of an efficient damping of acoustic energy, this setup represents a loss in active damping surface. Therefore, future works needs to address the in uence and requirements for the non-active parts (required size, coupling between neighboring non-active cavities, etc.) in order to find an efficient arrangement and investigate the actual de ection of the exible walls with the final aim of modeling liners with exible structures accurately.