126 Alleviation of low frequency noise by the soundproof opening built in Helmholtz resonators

With the rapid increase in automobiles, the importance of reducing low-frequency noise is being emphasized for a comfortable urban environment. Helmholtz resonators are widely used to attenuate low-frequency noise over a narrow range. In this study, a slit-type soundproof panel is designed to achieve low-frequency noise attenuation in the range of 500 Hz to 1000 Hz with the characteristics of a Helmholtz resonator and the ability to pass air through the slits on the panel surface for reducing wind load. The basic dimension of the soundproof panel is determined using the classical formula and numerical analysis using a commercial program, COMSOL Multiphysics, for transmission loss prediction. From the numerical study, it is identified that the transmission loss performance is improved compared to the basic design according to the shape change and configuration method of the Helmholtz resonator. Although the correlation according to the shape change and configuration method cannot be derived, it is confirmed that it can be used as an effective method for deriving a soundproof panel design that satisfies the basic performance.

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Multi-tonal low frequency noise control using Helmholtz resonators with complex cavity designs for aircraft cabin noise improvement

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-2569 ◽

2021 ◽

Vol 263 (2) ◽

pp. 3975-3986

Author(s):

Tenon Charly Kone ◽

Sebastian Ghinet ◽

Raymond Panneton ◽

Thomas Dupont ◽

Anant Grewal

Keyword(s):

Noise Control ◽

Transmission Loss ◽

Low Frequency ◽

Helmholtz Resonator ◽

Sound Insulation ◽

Frequency Noise ◽

Low Frequency Noise ◽

Low Frequencies ◽

Helmholtz Resonators ◽

Resonance Frequencies

The noise control at multiple tonal frequencies simultaneously, in the low frequency range, is a challenge for aerospace, ground transportation and building industries. In the past few decades, various low frequency noise control solutions based on acoustic metamaterial designs have been presented in the literature. These solutions showed promising performance and are considered a better alternative to conventional sound insulation materials. In the present investigation, it was noticed that subdividing the cavity of a Helmholtz resonator allowed the control of multi-tonal noise at several resonance frequencies simultaneously and a shift of the resonance peaks towards the low frequencies. This paper proposes concepts of Helmholtz resonators with subdivided cavities to improve the sound transmission loss (STL) performance and simultaneously control the noise at several tonal frequencies. HRs with cylindrical shaped cavities were embedded in a layer of porous material. The STL of the metamaterial noise insulation configuration was predicted using serial and parallel assemblies of transfer matrices (TMM) incorporating a thermo-viscous-acoustic approach to accurately account for the viscous and thermal losses of acoustic wave propagation within the metamaterial. The STL calculated using the proposed TMM approach were observed to be in excellent agreement with the finite element method (FEM) numerical results.

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