Effect of flow on an array of Helmholtz resonators: Is Kevlar a “magic layer”?

Abstract

The effects of flow on the acoustic behavior of metamaterials can be very significant and possibly destructive. To avoid these detrimental effects, it would be a good idea to have a “magic layer” that allows acoustics to pass through while suppressing the sound-flow interactions. A possible realization of this layer based on Kevlar fabric is tested in this paper. It is shown that, in the presence of Kevlar, flow-sound interactions that can lead to acoustic amplification and whistling phenomena are avoided. Thus, Kevlar will permit liner designs including large slits. However, it adds large acoustic losses, which limits interesting resonance effects in applications.

Acoustics of a double Helmholtz resonators with flow

“…It is therefore particularly important to take into account the effects of viscosity and flow in sufficient detail. These two effects can significantly alter the expected acoustic effects [15,16]. In this paper, this is illustrated by the case of a double Helmholtz resonator.…”

Perfect, broadband, and sub-wavelength absorption with asymmetric absorbers: Realization for duct acoustics with 3D printed porous resonators

“…The manufactured ABSA is mounted in the wall of a rectangular duct of inner height h w = 40 mm and width w w = 50 mm ended by an anechoic termination. This experimental facility and the associated measurement techniques have already been introduced and detailed in [42]. On each side of the sample, three microphones are placed and permit the measurements of the R + and T coefficients using a scattering matrix formalism.…”

Corona discharge actuator as an active sound absorber under normal and oblique incidence

“…The sample impedance is educed by an inverse method based on the multi-modal calculation of the acoustic field in a 2D lined channel with a uniform flow [29]. More details on the duct facility as well as on the measurement techniques used for grazing incidence and grazing flow experiments can be found in [30].…”