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Investigation on the Effects of Acoustic Liner Variation and Geometry Discontinuities on the Acoustic Performance of Lined Ducts

Amine Makni Mohamed Taktak Mabrouk Chaabane Mohamed Haddar
Archives of Acoustics | 2020 | vol. 45 | No 1 | 49-66 | DOI: 10.24425/aoa.2020.132481
Keywords absorbent systems effect discontinuities effect scattering matrix acoustic power attenuation
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Abstract

Noise reduction inside waveguide systems has gained momentum owing to a great interest in it. To attenuate the sound in a broad frequency range, this study aims to compare the effects of two acoustic liners, a perforated plate backed by an air cavity (PP-Air cavity), or by a porous material (PP-PM), on the acoustic behaviour of lined ducts using a numerical model to compute the multimodal scattering matrix. From this matrix, the reflection and the transmission coefficients are computed and therefore the acoustic power attenuation is deduced. Moreover, the effects of geometry of ducts with and without changes in the section are investigated. The numerical results are obtained for five configurations, including cases of narrowing and widening of a duct portion with sudden or progressive discontinuities. Accordingly, numerical coefficients of reflection and transmission as well as the acoustic power attenuation show the relative influence of acoustic liners in each type of configuration.

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Authors and Affiliations

Amine Makni
Mohamed Taktak
Mabrouk Chaabane
Mohamed Haddar

Identification of Physical Parameters of a Porous Material Located in a Duct by Inverse Methods

Kani Marwa Amine Makni Mohamed Taktak Mabrouk Chaabane Mohamed Haddar
Archives of Acoustics | 2021 | vol. 46 | No 4 | 657-665 | DOI: 10.24425/aoa.2021.139642
Keywords porous materials inverse methods scattering matrix acoustic power attenuation
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Abstract

Lined ducts with porous materials are found in many industrial applications. To understand and simulate the acoustic behaviour of these kinds of materials, their intrinsic physical parameters must be identified. Recent studies have shown the reliability of the inverse approach for the determination of these parameters. Therefore, in the present paper, two inverse techniques are proposed: the first is the multilevel identification method based on the simplex optimisation algorithm and the second one is based on the genetic algorithm. These methods are used of the physical parameters of a simulated case of a porous material located in a duct by the computation of its acoustic transfer, scattering, and power attenuation. The results obtained by these methods are compared and discussed to choose the more efficient one.
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Authors and Affiliations

Kani Marwa
1 2
Amine Makni
1
Mohamed Taktak
1 2
Mabrouk Chaabane
2
Mohamed Haddar
1
  1. Laboratory of Mechanics, Modeling and Productivity (LA2MP), National School of Engineers of Sfax, University of Sfax, Tunisia
  2. Faculty of Sciences of Sfax, University of Sfax, Tunisia

Evaluation of the Effect of Uncertainties on the Acoustic Behavior of a Porous Material Located in a Duct Element Using the Monte Carlo Method

Hanen Hannachi Hassen Trabelsi Marwa Kani Mohamed Taktak Mabrouk Chaabane Mohamed Haddar
Archives of Acoustics | 2023 | vol. 48 | No 1 | 81-91 | DOI: 10.24425/aoa.2023.144266
Keywords porous material physical parameters transmission loss acoustic power attenuation Monte Carlo method
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Abstract

When studying porous materials, most acoustical and geometrical parameters can be affected by the presence of uncertainties, which can reduce the robustness of models and techniques using these parameters. Hence, there is a need to evaluate the effect of these uncertainties in the case of modeling acoustic problems. Among these evaluation methods, the Monte Carlo simulation is considered a benchmark for studying the propagation of uncertainties in theoretical models. In the present study, this method is applied to a theoretical model predicting the acoustic behavior of a porous material located in a duct element to evaluate the impact of each input error on the computation of the acoustic proprieties such as the reflection and transmission coefficients as well as the acoustic power attenuation and the transmission loss of the studied element. Two analyses are conducted; the first one leads to the evaluation of the impacts of error propagation of each acoustic parameter (resistivity, porosity, tortuosity, and viscous and thermal length) through the model using a Monte Carlo simulation. The second analysis presents the effect of propagating the uncertainties of all parameters together. After the simulation of the uncertainties, the 95% confidence intervals and the maximum and minimum errors of each parameter are computed. The obtained results showed that the resistivity and length of the porous material have a great influence on the acoustic outputs of the studied model (transmission and reflection coefficients, transmission loss, and acoustic power attenuation). At the same time, the other physical parameters have a small impact. In addition, the acoustic power attenuation is the acoustic quantity least impacted by the input uncertainties.
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Authors and Affiliations

Hanen Hannachi
1 2
Hassen Trabelsi
1
Marwa Kani
1 2
Mohamed Taktak
3 4
Mabrouk Chaabane
2
Mohamed Haddar
2
  1. Laboratory of Mechanics, Modeling and Productivity (LA2MP), National School of Engineers of Sfax, University of Sfax, Sfax, Tunisia
  2. Faculty of Science of Sfax, University of Sfax, Sfax, Tunisia
  3. Laboratory of Mechanics, Modeling and Productivity (LA2MP), National School of Engineers of Sfax, University of Sfax, Tunisia
  4. Faculty of Sciences of Sfax, University of Sfax, Tunisia

Selection of Exposure Parameters for a HIFU Ablation System Using an Array of Thermocouples and Numerical Simulations

Łukasz Fura Tamara Kujawska
Archives of Acoustics | 2019 | vol. 44 | No 2 | 349-355 | DOI: 10.24425/aoa.2019.128498
Keywords automated HIFU ablation system threshold acoustic power of HIFU beam ex vivo tissue necrotic lesion thermocouple array
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Abstract

Image-guided High Intensity Focused Ultrasound (HIFU) technique is dynamically developing technology for treating solid tumors due to its non-invasive nature. Before a HIFU ablation system is ready for use, the exposure parameters of the HIFU beam capable of destroying the treated tissue without damaging the surrounding tissues should be selected to ensure the safety of therapy. The purpose of this work was to select the threshold acoustic power as well as the step and rate of movement of the HIFU beam, generated by a transducer intended to be used in the HIFU ablation system being developed, by using an array of thermocouples and numerical simulations. For experiments a bowl-shaped 64-mm, 1.05 MHz HIFU transducer with a 62.6 mm focal length (f-number 0.98) generated pulsed waves propagating in two-layer media: water/ex vivo pork loin tissue (50 mm/40 mm) was used. To determine a threshold power of the HIFU beam capable of creating the necrotic lesion in a small volume within the tested tissue during less than 3 s each tissue sample was sonicated by multiple parallel HIFU beams of different acoustic power focused at a depth of 12.6 mm below the tissue surface. Location of the maximum heating as well as the relaxation time of the tested tissue were determined from temperature variations recorded during and after sonication by five thermo-couples placed along the acoustic axis of each HIFU beam as well as from numerical simulations. The obtained results enabled to assess the location of each necrotic lesion as well as to determine the step and rate of the HIFU beam movement. The location and extent of the necrotic lesions created was verified using ultrasound images of tissue after sonication and visual inspection after cutting the samples. The threshold acoustic power of the HIFU beam capable of creating the local necrotic lesion in the tested tissue within 3 s without damaging of surrounding tissues was found to be 24 W, and the pause between sonications was found to be more than 40 s.

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Authors and Affiliations

Łukasz Fura
Tamara Kujawska

Evaluation of the Acoustic Performance of Porous Materials Lined Ducts with Geometric Discontinuities

Dhouha Tounsi Wafa Taktak Raja Dhief Mohamed Taktak Mabrouk Chaabane Mohamed Haddar
Archives of Acoustics | 2022 | vol. 47 | No 2 | 223-240 | DOI: 10.24425/aoa.2022.141652
Keywords geometric discontinuities in duct systems acoustic impedance porous materials perforated plate acoustic power attenuation
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Abstract

Duct silencers provide effective noise reduction for heating, ventilation and air conditioning systems. These silencers can achieve an excellent sound attenuation through the attributes of their design. The reactive silencer works on the principle of high reflection of sound waves at low frequencies. On the other hand, the dissipative silencer works on the principle of sound absorption, which is very effective at high-frequencies. Combining these two kinds of silencers allowed covering the whole frequency range. In this paper, the effect of liner characteristics composed of a perforated plate backed by a porous material and geometry discontinuities on the acoustic power attenuation of lined ducts is evaluated. This objective is achieved by using a numerical model to compute the multimodal scattering matrix, thus allowing deducing the acoustic power attenuation. The numerical results are obtained for six configurations, including cases of narrowing and widening of a radius duct with sudden or progressive discontinuities. Numerical acoustic power attenuation shows the relative influence of the variation in the values of each parameter of the liner, and of each type of radius discontinuities of ducts.
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Authors and Affiliations

Dhouha Tounsi
1
Wafa Taktak
2
Raja Dhief
1 3
Mohamed Taktak
1 3
Mabrouk Chaabane
3
Mohamed Haddar
1
  1. Mechanics, Modelling and Production Laboratory (LA2MP), Mechanical Department, National School of Engineers of Sfax, University of Sfax, Sfax, Tunisia
  2. National School of Engineers of Sfax, University of Sfax, Sfax, Tunisia
  3. Faculty of Sciences of Sfax, Sfax, Tunisia

The effect of a concentrated mass on the acoustic power and the resonant frequencies of a circular plate

Wojciech P. Rdzanek Krzysztof Szemela
Archives of Acoustics | 2022 | vol. 47 | No 4 | 529-538 | DOI: 10.24425/aoa.2022.142895
Keywords thin plate concentrated mass fluid-structure interactions resonant frequencies modal expansion acoustic power
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Abstract

This study presents an analysis of the effect of the concentrated mass on the acoustic power and the resonant frequencies of a vibrating thin circular plate. The fluid-structure interactions and the acoustic wave radiation effect have been included. The eigenfunction expansion has been used to express the transverse displacement of the plate. The appropriate number of modes is determined approximately to achieve physically correct results. Then highly accurate results are obtained numerically. The radiated acoustic power has been used to determine the resonant frequencies. The introducing of the concentrated mass is justified by modelling the added mass of the moving component of the exciter.
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Authors and Affiliations

Wojciech P. Rdzanek
1
Krzysztof Szemela
1
  1. University of Rzeszow, College of Natural Sciences, Institute of Physics, Rzeszow, Poland

Acoustic Power Radiated by a System of Two Vibrating Circular Membranes Located at the Boundary of Three-Wall Corner Spatial Region

Wojciech P. Rdzanek Krzysztof Szemela Witold J. Rdzanek
Archives of Acoustics | 2012 | vol. 37 | No 4 | 463-473 | DOI: 10.2478/v10168-012-0058-8
Keywords three-wall corner region Green function Neumann boundary value problem modal analysis asymmetric vibrations vibration of an excited circular membrane acoustic power mutual interaction of sound sources.
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Abstract

Two vibrating circular membranes radiate acoustic waves into the region bounded by three infinite baffles arranged perpendicularly to one another. The Neumann boundary value problem has been investigated in the case when both sources are embedded in the same baffle. The analyzed processes are time harmonic. The membranes vibrate asymmetrically. External excitations of different surface distributions and different phases have been applied to the sound sources’ surfaces. The influence of the radiated acoustic waves on the membranes’ vibrations has been included. The acoustic power of the sound sources system has been calculated by using a complete eigenfunctions system.

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Authors and Affiliations

Wojciech P. Rdzanek
Krzysztof Szemela
Witold J. Rdzanek

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