Numerical investigation of the sound-insulation effect of a suspended ceiling structure with arrayed Helmholtz resonators by the finite-difference time-domain method

Asakura, Takumi

doi:10.1016/j.apacoust.2020.107601

Cited by 7 publications

(6 citation statements)

References 28 publications

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“…where, A þ and A À indicate the same wave propagating in different directions, [84][85][86][87][88] and k þ and k À represents the wave numbers in terms of Mach number, given as:…”

Section: Discussionmentioning

confidence: 99%

“…The wavelength, λ is given by λ=2πc/ω. Hence, the equation can be expressed in terms of the wave number, where the wave number is defined as k=ω/c=2π/λ.Since harmonic plane waves are concerned, equation (47) can be further expressed by removing the aspect of time aswhere, A+ and A− indicate the same wave propagating in different directions, 84-88 and k+ and k− represents the wave numbers in terms of Mach number, given as: k+=ωc+ν=k1+M and k−=ωc−ν=k1−M To further simply equation (48), we introduce a modified wave number, K : K=k1−M2It brings the equation toEquation (49) is the 1-D equation for a harmonic wave propagating in a duct.…”

Section: Review Of 1d Plane Wave Equationsmentioning

confidence: 99%

“…Since harmonic plane waves are concerned, equation (47) can be further expressed by removing the aspect of time aswhere, A+ and A− indicate the same wave propagating in different directions, 84-88 and k+ and k− represents the wave numbers in terms of Mach number, given as: k+=ωc+ν=k1+M and k−=ωc−ν=k1−M To further simply equation (48), we introduce a modified wave number, K : K=k1−M2…”

Section: Review Of 1d Plane Wave Equationsmentioning

confidence: 99%

“…Here we also consider the effects (1) acoustic porous materials, (2) the grazing flow Mach number. This is aimed to identify the optimum design for combustion engine applications [74][75][76][77][78][79][80][81][82][83][84][85] . Before the case study is presented, it would be informative to overview of theoretically predicting the resonant frequency of Helmholtz resonators and characterizing the resonator's acoustic damping performances in various ways.…”

Section: Introductionmentioning

confidence: 99%

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Case studies on aeroacoustics damping performances of Coupled Helmholtz Resonators over low frequency ranges

Zhang

Win

2022

Journal of Low Frequency Noise, Vibration and Active Control

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Helmholtz resonators are widely applied in industries to reduce the transmission of unwanted noise and passively attenuate tonal noise in pipes/ducts. For example, internal combustion engines take advantage of Helmholtz resonators by combining air box, subwoofers and perforated pipes/plates to reduce engine noise emission nowadays. However, the main drawback of the conventional Helmholtz resonators includes a very narrow bandwidth. To broaden the effective noise damping frequency range of Helmholtz resonators, a number of different improved designs are reported and tested recently in the literature such as applying an array of separated resonators or implementing mechanical-coupled Helmholtz resonators. In this work, we conduct a brief review on the aeroacoustics damping performance of coupled Helmholtz resonators over low frequency range. The noise damping performances could be characterized and quantified in terms of transmission loss and sound absorption coefficient. Both definitions are discussed. Comparison is then made between the separately working resonators and the mechanical-coupled ones. This is achieved by replacing the sharable flexible sidewall with a rigid sidewall. The effect of the mean grazing flow is also discussed and examined on the noise damping performances. An experimental case study of the present authors is included. Additionally, to improve the noise damping performance further, an overview of the resonators neck with different noise damping materials inserted is conducted. Finally, 3D numerical approaches in simulating the aeroacoustics damping performances of coupled Helmholtz resonators are reviewed. This case study and brief overview provides a guidance on improving the design of coupled Helmholtz resonators and an array of Helmholtz resonators.

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“…where, A þ and A À indicate the same wave propagating in different directions, [84][85][86][87][88] and k þ and k À represents the wave numbers in terms of Mach number, given as:…”

Section: Discussionmentioning

confidence: 99%

Section: Review Of 1d Plane Wave Equationsmentioning

confidence: 99%

Section: Review Of 1d Plane Wave Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Case studies on aeroacoustics damping performances of Coupled Helmholtz Resonators over low frequency ranges

Zhang

Win

2022

Journal of Low Frequency Noise, Vibration and Active Control

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“…They have been used also in the acoustic treatment of broadcasting studios [13] and conference rooms [14]. They have also been used to suppress specific eigenmodes in a room [15] and also to form a construction as a suspended ceiling [16]. Their sound absorption has been extensively studied [17,18] and various improvements have been proposed [19,20].…”

Section: Introductionmentioning

confidence: 99%

Tunable Helmholtz Resonators Using Multiple Necks

Papadakis,

Stavroulakis

2023

Micromachines

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One of the uses of Helmholtz resonators is as sound absorbers for room acoustic applications, especially for the low frequency range. Their efficiency is centered around their resonance frequency which mainly depends on elements of their geometry such as the resonator volume and neck dimensions. Incorporating additional necks on the body of a Helmholtz resonator (depending on whether they are open or closed) has been found to alter the resulting resonance frequency. For this study, tunable Helmholtz resonators to multiple resonance frequencies, are proposed and investigated utilizing additional necks. The resonance frequencies of various multi-neck Helmholtz resonators are first modeled with the use of the finite element method (FEM), then calculated with the use of an analytical approach and the results of the two approaches are finally compared. The results of this study show that Helmholtz resonators with multiple resonances at desired frequencies are achievable with the use of additional necks, while FEM and analytical methods can be used for the estimation of the resonance frequencies. Analytical and FEM approach results show a good agreement in cases of small number of additional necks, while the increasing differences in cases of higher neck additions, were attributed to the change in effective length of the necks as demonstrated by FEM. The proposed approach can be useful for tunable sound absorbers for room acoustics applications according to the needs of a space. Also, this approach can be applied in cases of additional tunable air resonances of acoustic instruments (e.g., string instruments).

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