The effects of wedge geometrical parameters and arrangement on the sound absorption coefficient – A numerical and experimental study

Nejad, Mohammad Erfan Tavakkoli; Loghmani, Ali; Ziaei-Rad, Saeed

doi:10.1016/j.apacoust.2020.107458

Cited by 7 publications

(23 citation statements)

References 11 publications

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“…A speaker at the beginning of the tube generates a plane wave with an amplitude of 1 Pa. The element type of the meshing process is considered tetrahedral element with a minimum size of 0.001 m and a maximum size of 0.1994 m which is one-tenth of the smallest wavelength according to the reference 5 .…”

Section: Finite Element Modelmentioning

confidence: 99%

“…with the optimum dimensions mentioned in the second row of Table 5 is placed in an impedance tube simulated in COMSOL Multiphysics to evaluate the effect of the air gap thickness (Figure 9(a)) on the sound absorption coefficient and then the air gap thickness, from absorber's back to the solid wall at the end of the impedance tube, is changed from 0 to 15 cm in four intervals to compare with the results of reference. 5 It should be noted that, according to the ISO 10534-2 standard, 18 the distance between the furthest microphone and the tip of the chamfered pyramid must change when calculating the sound absorption coefficient each time the air gap thickness is altered since the height of the chamfered pyramid does not change. Sound absorption coefficient results of the optimum chamfered pyramid and reference 5 wedge in three different modes are reported in Figure 9(b).…”

Section: Evaluating the Effect Of Air Gap Thickness On The Sound Abso...mentioning

confidence: 99%

“…As a result, it is critical to develop ideal sound absorbers for the anechoic chamber that have the highest sound absorption while being the thinnest. The sound absorbers of the anechoic chamber could be flat, 4 wedge, 5 conical, 6 or pyramidshaped. 1 Wave method, 7 numerical methods (like the finite element method 6,7 and finite difference time-domain method 8 ) and experimental methods (including measuring the sound absorption coefficient of perpendicular impact in the impedance tube [9][10][11][12] and the actual sound absorption coefficient in the reverberation room 1 ) can be used to determine the absorption coefficient of sound absorbers.…”

Section: Introductionmentioning

confidence: 99%

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Analysis and optimization of the chamfered pyramid and evaluation of geometrical parameters’ effect on its sound absorption coefficient

Moradi,

Basirjafari

2024

Building Acoustics

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Since symmetrical geometry makes it easier to arrange pyramid absorbers on anechoic chamber walls compared to wedge absorbers, the goal of this paper is to present an optimal pyramid-shaped absorber which, in addition to the optimal performance in sound absorption, has other advantages such as less thickness, lower material consumption and cost, easier construction, arrangement and maintenance and occupying less space compared to wedges. The COMSOL Multiphysics software was used to simulate the optimized sound absorber by using the genetic algorithm programed in MATLAB software, with the goal of a 100 Hz cut-off frequency. The results show that the optimized chamfered pyramid at the top performs better at sound absorption compared to the complete pyramid and wedge with 18% less thickness. Furthermore, the cut-off frequency decreased to 91 Hz when a gap of up to 15 mm was created between the adjacent absorbers mounted on the surface, which is desirable.

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Section: Finite Element Modelmentioning

confidence: 99%

Section: Evaluating the Effect Of Air Gap Thickness On The Sound Abso...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis and optimization of the chamfered pyramid and evaluation of geometrical parameters’ effect on its sound absorption coefficient

Moradi,

Basirjafari

2024

Building Acoustics

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“…The measurement was performed inside and outside the acoustic chamber, as shown in Figure 3, at a time when no product was tested, so that we could verify only the properties of the acoustic chamber, respectively the EN, as shown in Figure 4. The damping rate of the chamber depends on the shape and material of its tiling [32,33].…”

Section: Environmental Noise and Features Of The Anechoic Chambermentioning

confidence: 99%

Influence of Environmental Noise on Quality Control of HVAC Devices Based on Convolutional Neural Network

et al. 2021

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Testing the quality of manufactured products based on their sound expression is becoming popular nowadays. To maintain low production costs, the testing is processed at the end of the assembly line. Such measurements are affected considerably by the factory noise even though they are performed in anechoic chambers. Before designing the quality control algorithm based on a convolutional neural network, we do not know the influence of the factory noise on the success rate of the algorithm that can potentially be obtained. Therefore, this contribution addresses this problem. The experiments were undertaken on a synthetic dataset of heat, ventilation, and air-conditioning devices. The results show that classification accuracy of the decision-making algorithm declines more rapidly at a high level of environmental noise.

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“…Absorbers are porous materials that absorb sound energy, while barriers are dense materials reflecting the sound and preventing sound propagation. In passive methods, it is required that the absorber or barrier depth be thick enough depending on the desired frequency to diminish the sound effectively (Tavakkoli Nejad et al, 2020; Vér, 2005). Thus, passive methods are effective for frequencies higher than 1 kHz.…”

Section: Introductionmentioning

confidence: 99%

Active noise control for global broadband noise attenuation in a cylindrical cavity using Modal FxLMS algorithm

Iranpour

Loghmani

Danesh

2022

Journal of Vibration and Control

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Noise reduction is very important for cavities such as long ventilation ducts, and train and airplane cabins. This paper seeks to develop, design, and implement an active noise control system to globally reduce narrowband and broadband acoustic noises inside a cylindrical cavity using the Modal FxLMS algorithm along with canceling the feedback effect of the actuator on the reference microphone. In addition, the efficiency of the proposed algorithm is compared to the conventional FxLMS algorithm for broadband noises in terms of acoustic potential energy and energy consumption of the actuators. To this end, the natural frequencies and mode shapes are derived using experimental methods and finite element simulation, and the results are compared. The modal data are used to design and implement a modal filter. The filter output is fed to the Modal FxLMS algorithm as the error signal for updating controller coefficients. Due to the presence of a reference microphone for the proposed algorithm and the effect of the control loudspeaker, it is required to remove the feedback effect. An experimental setup is developed, and an FPGA board and LabVIEW software are adopted to implement and verify the effectiveness of the proposed algorithm. The results indicate that the controller could effectively attenuate the narrowband and broadband acoustic noises globally. Furthermore, although the conventional FxLMS algorithm can suppress the noise around acoustic modes, it produces a larger control signal than the Modal FxLMS algorithm and consumes more energy.

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The effects of wedge geometrical parameters and arrangement on the sound absorption coefficient – A numerical and experimental study

Cited by 7 publications

References 11 publications

Analysis and optimization of the chamfered pyramid and evaluation of geometrical parameters’ effect on its sound absorption coefficient

Analysis and optimization of the chamfered pyramid and evaluation of geometrical parameters’ effect on its sound absorption coefficient

Influence of Environmental Noise on Quality Control of HVAC Devices Based on Convolutional Neural Network

Active noise control for global broadband noise attenuation in a cylindrical cavity using Modal FxLMS algorithm

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