scholarly journals High-Temperature and Low-Frequency Acoustic Energy Absorption by a Novel Porous Metamaterial Structure

2021 ◽  
Author(s):  
Qihang Liu ◽  
Xuewei Liu ◽  
Chuanzeng Zhang ◽  
Fengxian Xin
Keyword(s):  
High Temperature ◽  
Theoretical Model ◽  
Porous Material ◽  
Energy Absorption ◽  
Low Frequency ◽  
Acoustic Energy ◽  
Frequency Range ◽  
Metamaterial Structure ◽  
Equivalent Inclusion ◽  
Absorption Performance

AbstractIn this paper, we propose a novel porous metamaterial structure with an improved acoustic energy absorption performance at high-temperature and in the low-frequency range. In the proposed novel porous metamaterial structure, a porous material matrix containing periodically perforated cylindrical holes arranged in a triangular lattice pattern is applied, and additional interlayers of another porous material are introduced around these perforations. The theoretical model is established by adopting the double porosity theory for the interlayer and the cylindrical hole which form an equivalent inclusion and then applying the homogenization method to the porous metamaterial structure formed by the equivalent inclusion and the porous matrix. The temperature-dependent air and material parameters are considered in the extended theoretical model, which is validated by the finite element results obtained by COMSOL Multiphysics. The acoustic or sound energy absorption performance can be improved remarkably at very low frequencies and high temperature. Furthermore, the underlying acoustic energy absorption mechanism inside the unit-cell is investigated by analyzing the distribution of the time-averaged acoustic power dissipation density and the energy dissipation ratio of each constituent porous material. The results reveal that regardless of the temperature, the acoustic energy is mostly dissipated in the porous material with a lower airflow resistivity, while the acoustic energy dissipated in the porous material with a higher airflow resistivity also becomes considerable in the high-frequency range. The novel porous metamaterial structure proposed in this paper can be efficiently utilized to improve the acoustic energy absorption performance at high temperature.

scholarly journals Diffuse Sound Absorptive Properties of Parallel-Arranged Perforated Plates with Extended Tubes and Porous Materials

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1091 ◽  
Author(s):  
Dengke Li ◽  
Daoqing Chang ◽  
Bilong Liu
Keyword(s):  
Boundary Condition ◽  
Porous Material ◽  
Porous Materials ◽  
Sound Absorption ◽  
Azimuthal Angle ◽  
Octave Band ◽  
Frequency Range ◽  
Absorption Coefficients ◽  
Perforated Plates ◽  
Absorption Performance

The diffuse sound absorption was investigated theoretically and experimentally for a periodically arranged sound absorber composed of perforated plates with extended tubes (PPETs) and porous materials. The calculation formulae related to the boundary condition are derived for the periodic absorbers, and then the equations are solved numerically. The influences of the incidence and azimuthal angle, and the period of absorber arrangement are investigated on the sound absorption. The sound-absorption coefficients are tested in a standard reverberation room for a periodic absorber composed of units of three parallel-arranged PPETs and porous material. The measured 1/3-octave band sound-absorption coefficients agree well with the theoretical prediction. Both theoretical and measured results suggest that the periodic PPET absorbers have good sound-absorption performance in the low- to mid-frequency range in diffuse field.

scholarly journals Modifikasi Permukaan Elemen Peredam Bising Dengan Profil Berbentuk Prisma

2016 ◽  
Vol 6 (01) ◽  
Author(s):  
Hanif Azimut
Keyword(s):  
High Frequency ◽  
Sound Absorption ◽  
Coupling Effect ◽  
Low Frequency ◽  
The Other ◽  
Frequency Range ◽  
Closed Type ◽  
Wave Resonance ◽  
Half Wave ◽  
Absorption Performance

<p class="AbstractText">The influence of surface modification by using prism shaped profile on the sound absorption of absorber element was investigated experimentally. A prime number based configuration of the two types opened and closed type rism shaped profile inclusion was tested by using impedance tube according ASTM E1050 standard. The result shows that sound absorption at low frequency band below 200 Hz increased with the increasing of closed prism number. It is related to the coupling effect between the cavities of the absorber element and the prisms that changes reactance of the coupled structure. In the other side, a half wave resonance like effect occur on the use of opened prisms inclusion, which is increase the sound absorption performance at mid to high frequency range between 800 Hz to 1,25 kHz.  </p>

An Experimental Study on the Damping of a Steam Generator Tube With Gap Supports in Air and Water

2016 ◽  
Author(s):  
Heung Seok Kang ◽  
Kang Hee Lee ◽  
Chang Whan Shin ◽  
Chang Hoon Ha ◽  
Tae Jeung Park
Keyword(s):  
Theoretical Model ◽  
Steam Generator ◽  
Low Frequency ◽  
Empirical Correlation ◽  
Frequency Range ◽  
Fluid Damping ◽  
Practical Model ◽  
Inactive Mode ◽  
Plate Type ◽  
Good Agreement

In this study, we present an analysis and experiment on the fluid damping of a Steam Generator (SG) tube with one and several plate-type supports that are submerged under water. For the damping measurement, a short tube of 2.2 meters in length with one gap support as well as a long tube of up to 10 meters with 11 and 13 supports are used. To see a fluid effect through an analytical approach, Mulcahy’s theory on a tube with finite-length gap support and Pettigrew’s empirical correlation for SG design were reviewed. The theoretical model is good at predicting the fluid damping at the first mode in a low frequency range which is an inactive mode at the support, while the practical model is much better at the higher modes, which are active modes, rocking modes, at the support(s). Experimental results from the short length tube with single support shows good agreement with a previous measurement by other researchers. A theoretical model and empirical correlation are in good agreement. Our measurements from a longer tube with several supports are reasonable compared with the others. There is, however, a wide discrepancy between predictions by the two models. As compared with the whole measurements, the theoretical model seems to be a good guideline in a low frequency range, while an empirical model is relatively good guideline in a high frequency range. Based on the whole collected data, a new correlation modified from Pettigrew’s correlation is suggested.

scholarly journals Inelastic Behaviour of Ice Ih Single Crystals in the Low-Frequency Range Due to Dislocations

1978 ◽  
Vol 21 (85) ◽  
pp. 375-384 ◽  
Author(s):  
René Vassoille ◽  
Christian Maï ◽  
Joseph Perez
Keyword(s):  
High Temperature ◽  
Internal Friction ◽  
Single Crystals ◽  
Empirical Relation ◽  
Low Frequency ◽  
Frequency Range ◽  
High Temperature Range ◽  
Temperature Range ◽  
Inelastic Behaviour ◽  
Torsional Pendulum

Abstract The inelastic behaviour of ice Ih single crystals has been investigated by an inverted torsional pendulum in the low-frequency range. Three features are distinguished: (i) a relaxation peak previously observed by several authors in the higher-frequency range, (ii) an internal friction increasing with temperature in the high-temperature range (230–273 K), (iii) within this high-temperature range, internal friction becomes amplitude dependent, and this dependence becomes greater the greater the temperature. In this case, the internal friction has been interpreted in terms of movements of dislocations. Hence, the experimental results are interpreted with a model of internal friction based on an empirical relation for the velocity of dislocations. This model of internal friction is in fair agreement with experimental data . It is possible then to get an estimate of dislocation density. Hence it is shown that internal friction experiments can be useful in the study of the plastic behaviour of ice single crystals.

scholarly journals Raman Spectra of Quartz and Pb4+-Doped SiO2 Crystals at Different Temperature and Pressure

Crystals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 569 ◽  
Author(s):  
Xiuyan Chen ◽  
Wenjiang Feng ◽  
Guoying Zhang ◽  
Yan Gao
Keyword(s):  
High Temperature ◽  
Raman Spectra ◽  
Low Frequency ◽  
Raman Frequency ◽  
Frequency Range ◽  
High Temperature And Pressure ◽  
Temperature And Pressure

In order to seek for new Raman crystals, the manuscript presented the discussion on the Raman frequency of α-quartz, β-quartz, as well as Pb4+-doped SiO2 crystals at different temperature and pressure. The results demonstrated that as the pressure increased, the Raman lines shifted towards higher frequency for α-SiO2 crystal, while for β-SiO2 crystals, the main lines moved to lower frequency. Several new peaks were generated from the Pb4+-doped α-SiO2 crystals. The Pb4+-doped β-SiO2 crystals presented strong and ample Raman beams in the low-frequency range. The airfoil-shaped spectra appeared and broadened at high temperature and pressure. It could be inferred that the Pb4+-doped SiO2 crystals were excellent Raman crystal candidates.

scholarly journals Modifikasi Permukaan Elemen Peredam Bising dengan Profil Berbentuk Prisma

2016 ◽  
Vol 6 (01) ◽  
pp. 23
Author(s):  
Julius Indra Kusuma ◽  
H Harjana ◽  
Iwan Yahya
Keyword(s):  
High Frequency ◽  
Sound Absorption ◽  
Coupling Effect ◽  
Low Frequency ◽  
The Other ◽  
Frequency Range ◽  
Closed Type ◽  
Wave Resonance ◽  
Half Wave ◽  
Absorption Performance

The influence of surface modification by using prism shaped profile on the sound absorption of absorber element was investigated experimentally. A prime number based configuration of the two types opened and closed type rism shaped profile inclusion was tested by using impedance tube according ASTM E1050 standard. The result shows that sound absorption at low frequency band below 200 Hz increased with the increasing of closed prism number. It is related to the coupling effect between the cavities of the absorber element and the prisms that changes reactance of the coupled structure. In the other side, a half wave resonance like effect occur on the use of opened prisms inclusion, which is increase the sound absorption performance at mid to high frequency range between 800 Hz to 1.25 kHz.

scholarly journals Inelastic Behaviour of Ice Ih Single Crystals in the Low-Frequency Range Due to Dislocations

1978 ◽  
Vol 21 (85) ◽  
pp. 375-384
Author(s):  
René Vassoille ◽  
Christian Maï ◽  
Joseph Perez
Keyword(s):  
High Temperature ◽  
Internal Friction ◽  
Single Crystals ◽  
Empirical Relation ◽  
Low Frequency ◽  
Frequency Range ◽  
High Temperature Range ◽  
Temperature Range ◽  
Inelastic Behaviour ◽  
Torsional Pendulum

AbstractThe inelastic behaviour of ice Ih single crystals has been investigated by an inverted torsional pendulum in the low-frequency range. Three features are distinguished:(i) a relaxation peak previously observed by several authors in the higher-frequency range,(ii) an internal friction increasing with temperature in the high-temperature range (230–273 K),(iii) within this high-temperature range, internal friction becomes amplitude dependent, and this dependence becomes greater the greater the temperature.In this case, the internal friction has been interpreted in terms of movements of dislocations. Hence, the experimental results are interpreted with a model of internal friction based on an empirical relation for the velocity of dislocations. This model of internal friction is in fair agreement with experimental data . It is possible then to get an estimate of dislocation density. Hence it is shown that internal friction experiments can be useful in the study of the plastic behaviour of ice single crystals.

scholarly journals Influence of Sugar Palm Ash Fraction and Resonator Configuration on Acoustic Absorption Performance of Expose Brick

2016 ◽  
Vol 4 (01) ◽  
pp. 19
Author(s):  
Zulfa Kamila R ◽  
Iwan Yahya ◽  
Utari U
Keyword(s):  
Performance Improvement ◽  
Performance Optimization ◽  
Sound Absorption ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Raw Material ◽  
Frequency Range ◽  
Helmholtz Resonators ◽  
Resonator Structure ◽  
Absorption Performance

<span>Sound absorption performance optimization of expose brick has been conducted in associated with <span>the fraction of sugar palm ash in its raw material and configuration of Helmholtz resonators inside <span>the brick structure. The testing was conducted experimentally refer to ASTM E-1050-98 standard <span>procedure. In this case there are three variations sugar palm ash fractions of 0%, 5%, and 10%, as <span>well as two array resonator configurations. The results showed that the brick with fraction of 10% <span>sugar palm ash has the best sound absorption performance. As for the configuration of array <span>identical Helmholtz resonator giving better performance improvement at low frequency span than <span>complex resonator structure with coupled cavity where the best performance occur on(376-488) <span>Hz frequency range with the absorption coefficient α of 0.54.</span></span></span></span></span></span></span></span><br /></span>

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

Dynamic Damping and Stiffness Characteristics of the Rolling Tire

2001 ◽  
Vol 29 (4) ◽  
pp. 258-268 ◽  
Author(s):  
G. Jianmin ◽  
R. Gall ◽  
W. Zuomin
Keyword(s):  
Dynamic Behavior ◽  
Variable Parameter ◽  
Low Frequency ◽  
Vertical Load ◽  
Frequency Range ◽  
Inflation Pressure ◽  
Vehicle Simulation ◽  
Dynamic Damping ◽  
Speed Range ◽  
Stiffness Characteristics

Abstract A variable parameter model to study dynamic tire responses is presented. A modified device to measure terrain roughness is used to measure dynamic damping and stiffness characteristics of rolling tires. The device was used to examine the dynamic behavior of a tire in the speed range from 0 to 10 km/h. The inflation pressure during the tests was adjusted to 160, 240, and 320 kPa. The vertical load was 5.2 kN. The results indicate that the damping and stiffness decrease with velocity. Regression formulas for the non-linear experimental damping and stiffness are obtained. These results can be used as input parameters for vehicle simulation to evaluate the vehicle's driving and comfort performance in the medium-low frequency range (0–100 Hz). This way it can be important for tire design and the forecasting of the dynamic behavior of tires.

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