The Perforated Panel Resonator with Flexible Tube Bundles and its Appliations

Abstract

The sound absorptive mechanism and properties of the perforated panel resonator with flexible tube bundles are presented. Based upon that, some practical applications of the sound absorbing structure are introduced as follows. First of all, the perforated panel resonator with flexible tube bundles is used in designing a highly sound absorptive chamber, which is used as an audio-video laboratory. The acoustical performances of the chamber are presented. Second, the perforated panel resonator with flexible tube bundles is used in highly efficient duct silencer. The total noise level of axial fan source is attenuated to background noise level. Not only middle and high frequency noise is reduced, but also low frequency noise is suppressed considerably. Third, the perforated panel resonator with flexible tube bundles is used in a small-type centrifugal fan's casing treatments. The cut-off region of the centrifugal fan's casing is also acoustically treated. After the acoustical treatments, total sound power level of the fan is reduced obviously. Fourth, the perforated panel resonator with flexible tube bundles is used in designing the exhaust ducts and sound absorptive channel walls for an electrical transformer substation. The noise emitted from the transformer substation is reduced to surrounding background noise level.

Long Elastic Open Neck Acoustic Resonator for low frequency absorption

“…if h l t > , essentially because of a significant reduction of cavity volume. 11), compared to the classical Helmholtz formulation or Lu et al [17] approach applied to long tubes. Fig.…”

“…A possible approach could be to include, in a Helmholtz resonator, a winding neck extension built at the upper surface for tuning at a low frequency [16], or to link an upper perforated panel with flexible tubes introduced in the cavity, as proposed by Lu et al [17].…”

“…In these configurations, incident acoustic waves are damped in a long resistive and reactive medium (winding neck extension [16] or flexible tubes [17]) before being transmitted in the cavity. The interface with the cavity generates a low resonance frequency by a prolongation of the air column length The interest of this concept has been proven experimentally by these last authors but without any mathematical model to allow for determination of the absorption frequency range according to dimensional parameters.…”

Targeted sound attenuation capacity of 3D printed noise cancelling waveguides

“…Where these pioneering works established the attenuation potential that can be achieved, none of these works characterised the transmission loss associated. Other notable works building on geometrical parameters combined the principles of Helmholtz resonators with flexible tubes and neck extensions by Shinsuke [31] and Lu [32]. Attenuation of high amplitude pulses using a lattice of Helmholtz resonators was studied by Olivier [33] and reported a nonlinear absorption.…”

Low frequency sound absorption of resonators with flexible tubes

“…Nevertheless, their physical law is not suited to an absorption to the lowest frequencies, as needed for future Ultra High Bypass Ratio (UHBR) engines with shorter and thinner nacelles (frequencies around 500 Hz). A possible approach could be to link the perforated panel with flexible tubes introduced in the cavity, as proposed by Lu et al [9], thus to shift the resonance frequency to a lower frequency by a prolongation of air column length. The interest of this concept has been proved experimentally but the authors have used a mathematical model based on a thin perforated plate (i.e.…”