Duct Noise Control by Using Very Light Composite Plate

2011 ◽  
Vol 410 ◽  
pp. 361-365
Author(s):  
Y.S. Choy ◽  
Yang Liu ◽  
Kin Tak Lau
Keyword(s):  
Theoretical Study ◽  
Noise Control ◽  
Transmission Loss ◽  
Low Frequency ◽  
Composite Plates ◽  
Bending Stiffness ◽  
Composite Panel ◽  
Frequency Noise ◽  
Reinforced Composite ◽  
Flow Through

A compact flow-through plate silencer is constructed for low frequency noise control by using new reinforced composite plates. The concept comes from the previous theoretical study [1] that in a duct, a clamped supported plate covered with a rigid cavites. The structural property of the very light plate with high bending stiffness is very crucial element in such plate silencer. In this study, an approach to fabricate new reinforced composite panel with light weight and high bending stiffness is developed in order to realize the function of this plate silencer practically. The performance of two plate silencer with the stopband from 229 to 618Hz in which the transmission loss is higher than 10 dB over the whole frequency band can be achieved.

scholarly journals Low-frequency vibro-acoustic response of an optimized fiber-reinforced graphite truss sandwich panel filled with wood-based material

2021 ◽  
pp. 146134842110229
Author(s):  
Luyao Wang ◽  
Liming Dai ◽  
Gang Hu
Keyword(s):  
Noise Control ◽  
Transmission Loss ◽  
Low Frequency ◽  
Sandwich Panels ◽  
Weight Ratio ◽  
Frequency Noise ◽  
Fiber Reinforced ◽  
Acoustic Response ◽  
Acoustic Characteristics ◽  
Fiber Materials

Conventional metallic sandwich panels are widely used for noise control owing to their good noise control capabilities and excellent mechanical strength-to-weight ratio property. Furthermore, sound-absorbing products consisting of glass or mineral fiber materials are generally filled into the sandwich structures to lower the vibration response in resonance frequency and to enhance the structural noise attenuation capacity. In the present study, a fiber-reinforced graphite material is used as an alternative to its metallic counterparts. Moreover, a wood-based renewable absorption material is used as the absorption material and is filled into the sandwich structural core. The vibro-acoustic characteristics of the panel with such a design are numerically investigated using Actran. The findings of the research indicate that the proposed sandwich structure achieves advanced low-frequency noise control performance in comparison with other conventional metallic sandwich panels. Approximately 7 dB increase in sound transmission loss in the audible-frequency range is achieved in addition to a reduced panel weight and more stable vibration with reduced amplitude. The existing data available in the literature are employed for validating and illustrating the accuracy and reliability of the proposed approach.

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

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.

scholarly journals Acoustic notch filtering earmuff utilizing Helmholtz resonator arrays

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0258842
Author(s):  
Fumiya Mizukoshi ◽  
Hidetoshi Takahashi
Keyword(s):  
Resonant Frequency ◽  
Noise Control ◽  
Active Noise Control ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Honeycomb Structure ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Target Frequency ◽  
Notch Filtering

In recent years, noisy bustling environments have created situations in which earmuffs must soundproof only specific noise while transmitting significant sounds, such as voices, for work safety and efficiency. Two sound insulation technologies have been utilized: passive noise control (PNC) and active noise control (ANC). However, PNC is incapable of insulating selective frequencies of noise, and ANC is limited to low-frequency sounds. Thus, it has been difficult for traditional earmuffs to cancel out only high-frequency noise that people feel uncomfortable hearing. Here, we propose an acoustic notch filtering earmuff utilizing Helmholtz resonator (HR) arrays that provides a sound attenuation effect around the tuneable resonant frequency. A sheet-like sound insulating plate comprising HR arrays is realized in a honeycomb structure. Since the resonant frequency is determined by the geometry of the HR arrays, a highly audible sound region can be designed as the target frequency. In this research, the acoustic notch filtering performance of the proposed HR array plate is investigated in both simulations and experiments. Furthermore, the fabricated earmuffs using the novel HR array plates achieve a sound insulation performance exceeding 40 dB at the target frequency, which is sufficiently high compared to that of conventional earmuffs. The experimental results confirm that the proposed device is a useful approach for insulating frequency-selective sound.

Low-frequency noise control using layered granular aerogel and limp porous media

2021 ◽  
Vol 263 (4) ◽  
pp. 2724-2729
Author(s):  
Yutong Xue ◽  
Amrutha Dasyam ◽  
J. Stuart Bolton ◽  
Bhisham Sharma
Keyword(s):  
Noise Control ◽  
Glass Fibers ◽  
Low Frequency ◽  
Normal Incidence ◽  
Frequency Noise ◽  
Fibrous Materials ◽  
Low Frequency Noise ◽  
Frequency Range ◽  
Fibrous Media ◽  
Impedance Tube Method

The acoustic absorption of granular aerogel layers with a granule sizes in the range of 2 to 40 μm is dominated by narrow-banded, high absorption regions in the low-frequency range and by reduced absorption values at higher frequencies. In this paper, we investigate the possibility of developing new, low-frequency noise reduction materials by layering granular aerogels with traditional porous sound absorbing materials such as glass fibers. The acoustic behavior of the layered configurations is predicted using the arbitrary coefficient method, wherein the granular aerogel layers are modeled as an equivalent poro-elastic material while the fibrous media and membrane are modeled as limp media. The analytical predictions are verified using experimental measurements conducted using the normal incidence, two-microphone impedance tube method. Our results show that layered configurations including granular aerogels, fibrous materials, and limp membranes provide enhanced sound absorption properties that can be tuned for specific noise control applications over a broad frequency range.

scholarly journals Study of a Nonlinear Membrane Absorber Applied to 3D Acoustic Cavity for Low Frequency Broadband Noise Control

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1138 ◽  
Author(s):  
Jianwang Shao ◽  
Tao Zeng ◽  
Xian Wu
Keyword(s):  
Degrees Of Freedom ◽  
Noise Control ◽  
Normal Modes ◽  
Low Frequency ◽  
Harmonic Balance Method ◽  
Nonlinear Normal Modes ◽  
Broadband Noise ◽  
Frequency Noise ◽  
Acoustic Cavity ◽  
Nonlinear Membrane

As a new approach to passive noise control in low frequency domain, the targeted energy transfer (TET) technique has been applied to the 3D fields of acoustics. The nonlinear membrane absorber based on the TET can reduce the low frequency noise inside the 3D acoustic cavity. The TET phenomenon inside the 3D acoustic cavity has firstly investigated by a two degrees-of-freedom (DOF) system, which is comprised by an acoustic mode and a nonlinear membrane without the pre-stress. In order to control the low frequency broadband noise inside 3D acoustic cavity and consider the influence of the pre-stress for the TET, a general model of the system with several acoustic modes of 3D acoustic cavity and one nonlinear membrane is built and studied in this paper. By using the harmonic balance method and the numerical method, the nonlinear normal modes and the forced responses are analyzed. Meanwhile, the influence of the pre-stress of the nonlinear membrane for the TET is investigated. The desired working zones of the nonlinear membrane absorber for the broadband noise are investigated. It can be helpful to design the nonlinear membrane according the dimension of 3D acoustic cavity to control the low frequency broadband noise.

scholarly journals Plate-Type Acoustic Metamaterials: Experimental Evaluation of a Modular Large-Scale Design for Low-Frequency Noise Control

Acoustics ◽  
2019 ◽  
Vol 1 (2) ◽  
pp. 354-368 ◽  
Author(s):  
Linus Ang ◽  
Yong Koh ◽  
Heow Lee
Keyword(s):  
Large Scale ◽  
Noise Control ◽  
Traffic Noise ◽  
Low Frequency ◽  
Industrial Applications ◽  
Frequency Noise ◽  
Acoustic Metamaterials ◽  
Scale Design ◽  
Stress Uniformity ◽  
Plate Type

For industrial applications, the scalability of a finalised design is an important factor to consider. The scaling process of typical membrane-type acoustic metamaterials may pose manufacturing challenges such as stress uniformity of the membrane and spatial consistency of the platelet. These challenges could be addressed by plate-type acoustic metamaterials with an internal tonraum resonator. By adopting the concept of modularity in a large-scale design (or meta-panel), the acoustical performance of different specimen configurations could be scaled and modularly combined. This study justifies the viability of two meta-panel configurations for low-frequency (80–500 Hz) noise control. The meta-panels were shown to be superior to two commercially available noise barriers at 80–500 Hz. This superiority was substantiated when the sound transmission class (STC) and the outdoor-indoor transmission class (OITC) were compared. The meta-panels were also shown to provide an average noise reduction of 22.7–27.4 dB at 80–400 Hz when evaluated in different noise environments—traffic noise, aircraft flyby noise, and construction noise. Consequently, the meta-panel may be further developed and optimised to obtain a design that is lightweight and yet has good acoustical performance at below 500 Hz, which is the frequency content of most problematic noises.

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