Maximum Sound Absorption by a Monopole in a Room at Low Frequencies

2020 ◽  
Vol 66 (3) ◽  
pp. 320-323
Author(s):  
N. G. Kanev
Keyword(s):  
Sound Absorption ◽  
Low Frequencies

scholarly journals Dual UV-Thermal Curing of Biobased Resorcinol Epoxy Resin-Diatomite Composites with Improved Acoustic Performance and Attractive Flame Retardancy Behavior

2021 ◽  
Vol 2 (1) ◽  
pp. 24-48
Author(s):  
Quoc-Bao Nguyen ◽  
Henri Vahabi ◽  
Agustín Rios de Anda ◽  
Davy-Louis Versace ◽  
Valérie Langlois ◽  
...  
Keyword(s):  
Heat Release ◽  
Flame Retardant ◽  
Epoxy Resin ◽  
Flame Retardancy ◽  
Sound Absorption ◽  
Flexural Modulus ◽  
Construction Materials ◽  
Acoustic Properties ◽  
Low Frequencies ◽  
Compacting Pressure

This study has developed novel fully bio-based resorcinol epoxy resin–diatomite composites by a green two-stage process based on the living character of the cationic polymerization. This process comprises the photoinitiation and subsequently the thermal dark curing, enabling the obtaining of thick and non-transparent epoxy-diatomite composites without any solvent and amine-based hardeners. The effects of the diatomite content and the compacting pressure on microstructural, thermal, mechanical, acoustic properties, as well as the flame behavior of such composites have been thoroughly investigated. Towards the development of sound absorbing and flame-retardant construction materials, a compromise among mechanical, acoustic and flame-retardant properties was considered. Consequently, the composite obtained with 50 wt.% diatomite and 3.9 MPa compacting pressure is considered the optimal composite in the present work. Such composite exhibits the enhanced flexural modulus of 2.9 MPa, a satisfying sound absorption performance at low frequencies with Modified Sound Absorption Average (MSAA) of 0.08 (for a sample thickness of only 5 mm), and an outstanding flame retardancy behavior with the peak of heat release rate (pHRR) of 109 W/g and the total heat release of 5 kJ/g in the pyrolysis combustion flow calorimeter (PCFC) analysis.

A multilayer microperforated panel prototype for broadband sound absorption at low frequencies

2019 ◽  
Vol 146 ◽  
pp. 134-144 ◽  
Author(s):  
F. Bucciarelli ◽  
G.P. Malfense Fierro ◽  
M. Meo
Keyword(s):  
Sound Absorption ◽  
Low Frequencies ◽  
Broadband Sound

scholarly journals DESAIN OF ACOUSTIC SANDWICH COMPOSITE FROM FOAM CONCRETE AND PALM FIBER

2018 ◽  
Vol 18 (2) ◽  
pp. 72-76
Author(s):  
Devya Kartika Devya ◽  
Mursal Mursal ◽  
Zulkarnain Djalil
Keyword(s):  
White Noise ◽  
Sound Absorption ◽  
Bottom Layer ◽  
Absorption Measurement ◽  
Sample Thickness ◽  
Sandwich Composite ◽  
Foam Concrete ◽  
Low Frequencies ◽  
Palm Fiber ◽  
Layer Composition

The purpose of this research were to investigate the influence of palm fiber composition and the number of hole cavities was varied with design Acoustic Sandwich Composite on sound absorption of acoustic panel. Acoustic panel were made of palm fiber as core and foam concreate as skin upper layer and bottom layer where there is a hole cavity on skin upper layer. Composition and the number of hole cavities was varied from 1 to 3 kg and the number of hole cavities from 25 to 81 hole. Sound absorption measurement was conducted by using reverberation room method based on ISO-354 (2003) with pink and white noise as sound source.The results showed that sample thickness affect acoustic absorption value effectively shifted at low frequencies, as in this research the best sound absorption occurs in panel with composition palm fiber most widely 3 kg, but coeffesient absorpsi value effective is in the range 250 Hz and use the number of hole cavities at skin upper layer of each sample effectively cause sound absorption coeffisient value increased, for both pink and white noise from sound source.Keyword : acoustic panel, foam concrete, palm fiber, sandwich composite, and absorption coefficient

Simulation research on low frequency sound absorption of monostable metamaterials

2021 ◽  
Vol 263 (6) ◽  
pp. 648-652
Author(s):  
Tuo Xing ◽  
Xianhui Li ◽  
Xiaoling Gai ◽  
Zenong Cai ◽  
Xiwen Guan
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Theoretical Model ◽  
Finite Element Simulation ◽  
Sound Absorption ◽  
Magnetic Force ◽  
Low Frequency ◽  
Low Frequencies ◽  
Element Simulation ◽  
Simulation Results

The monostable acoustic metamaterial is realized by placing a flexible panel with a magnetic proof mass in a symmetric magnetic field. The theoretical model of monostable metamaterials has been proposed. The method of finite element simulation is used to verify the theoretical model. The magnetic force of the symmetrical magnetic field is simplified as the relationship between force and displacement, acting on the mass. The simulation results show that as the external magnetic force increases, the peak sound absorption shifts to low frequencies. The theoretical and finite element simulation results are in good agreement.

scholarly journals Sound Absorption Performance of Sugar Palm Trunk Fibers

2019 ◽  
Vol 130 ◽  
pp. 01003
Author(s):  
Anditya Endar Prabowo ◽  
Kuncoro Diharjo ◽  
Ubaidillah ◽  
Iwan Prasetiyo
Keyword(s):  
Absorption Coefficient ◽  
Bulk Density ◽  
Sound Absorption ◽  
Random Noise ◽  
Air Gap ◽  
Sound Absorption Coefficient ◽  
Low Frequencies ◽  
Central Java ◽  
Absorption Performance ◽  
Small Medium Enterprises

The purpose of this research is to investigate the effect of bulk density, thickness, and air gap to sound absorption performance on absorber based sugar palm trunk fibers. The fibers were obtained from solid waste on Small-Medium Enterprises of sago flour processing in Klaten, Central Java, Indonesia. The absorber specimens were formed from the fibers using a simple press molding in an oven at 150 °C. According to ISO 10534-2, the absorber samples were tested using two microphones impedance tube with random noise source to get the curve of the sound absorption coefficient. The result shows that the absorption performance can be improved by increasing bulk density and increasing of sample thickness. Especially at low frequencies, improvement of the sound absorption coefficient can be achieved (NAC > 0.8) by applying the air gap behind the sample. The best performance of absorber based sugar palm trunk fiber can be achieved for (1 000 to 6 000) Hz range frequency.

scholarly journals Experimental Sound Absorption of Several Loose Uncooked Granular Materials

2019 ◽  
Vol 9 (1) ◽  
pp. 4578-4583
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Grain Shape ◽  
Experimental Tests ◽  
Sound Absorption Coefficient ◽  
Acoustic Absorption ◽  
Low Frequencies ◽  
Acoustic Insulation ◽  
Acoustic Absorption Coefficient ◽  
First Time

Absorbent materials it's an acoustic solution that can be used to control the reverberation time (RT) in deferent spaces as: conference rooms, in halls, theaters, cinema.... and also, it can be used in walls or ceilings of buildings to improve the acoustic insulation Which can be used for internal separations between spaces. This study focuses on the experimental study of the acoustic absorption coefficient of several granular food materials as a function of frequency 50 to 1600 Hz. All acoustic absorption tests performed in this study are performed by an acoustic impedance tube or Kundt tube. And to the knowledge of the author it is the first time in the literature that someone studies the acoustic behavior of this kind of materials. Several parameters were studied such as the effect of thickness on the sound absorption coefficient of the materials tested, like the influence of the grain form on the acoustic absorption by the introduction of a new parameter L / D, and finally the influence of density and type of material on the sound absorption coefficient. The objective of this work is to study the influence of the grain shape on the sound absorption coefficient, and that's why we have chosen these fifteen materials each one with its own shape. The results of these experimental tests show that when the sample thickness rises, the acoustic absorption coefficient rises too with a shift from resonance frequency to low frequencies. When the L/D parameter rises, the absorption behavior increases too in all frequencies mentioned. Finally, as the density of the tested material rises, the percentage of sound absorption of the materials also rises

An optimization method for reverberation room design

2021 ◽  
Vol 263 (4) ◽  
pp. 2360-2371
Author(s):  
Paul Didier ◽  
Cédric Van hoorickx ◽  
Edwin Reynders
Keyword(s):  
Sound Absorption ◽  
Sound Field ◽  
Optimization Procedure ◽  
Optimization Method ◽  
Finite Sample ◽  
Low Frequencies ◽  
Room Design ◽  
Target Values ◽  
Measured Absorption ◽  
Absorption Measurements

The ISO 354:2003 standard relating to sound absorption measurements is currently under revision to improve the reproducibility of the procedure it describes. Round robin tests conducted across various reverberation rooms indeed revealed significant disparities between sound absorption measurements of the same sample. One of the reasons is that, at low frequencies, the sound field in a single laboratory cannot be considered fully diffuse. However, the average sound field across different laboratories may be considered diffuse if the interaction between the finite sample and the diffuse field is duly accounted for and the direct field close to the absorber is disregarded. In this work, a method is developed for optimizing reverberation room design such that measured absorption values are as close as possible to ensemble average diffuse values. The reverberation room is modelled using the finite element method and standardized measurements of an absorptive sample are simulated. The distance between resulting absorption coefficients and diffuse target values is minimized in an optimization procedure having the geometrical characteristics of the model as input parameters. The results are anticipated to participate to the revised ISO 354 as guidelines for the construction of new reverberation rooms or the improvement of existing ones.

Measurement of sound absorption coefficient in a reverberant room using probability density function of damping constant

2021 ◽  
Vol 263 (4) ◽  
pp. 2940-2948
Author(s):  
Kosuke Goto ◽  
Takehiko Nakagawa ◽  
Yoshinari Yamada
Keyword(s):  
Probability Density Function ◽  
Absorption Coefficient ◽  
Spatial Variability ◽  
Measurement Method ◽  
Sound Absorption ◽  
Measurement Accuracy ◽  
Sound Absorption Coefficient ◽  
Reverberation Time ◽  
Low Frequencies ◽  
Sinusoidal Input

The measurement method of the sound absorption coefficient in a reverberation room is standardized in ISO 354. However, the measurement accuracy often deteriorates at low frequencies. This paper proposes a method that improves the measurement accuracy of the sound absorption coefficient at low frequencies. It calculates the sound absorption coefficient using reverberation time (RT) that is derived from the distribution of a damping constant for a sinusoidal input. The measured values by the proposed method were compared with those by the ISO 354 method. As a result, the proposed method reduces the spatial variability of RT and gives a better agreement with the statistical absorption coefficient that is calculated by a transfer matrix model at low frequencies.

scholarly journals A Basic Study on a Rectangular Plane Space Sound Absorber Using Permeable Membranes

2019 ◽  
Vol 11 (7) ◽  
pp. 2185 ◽  
Author(s):  
Sakagami ◽  
Okuzono ◽  
Somatomo ◽  
Funahashi ◽  
Toyoda
Keyword(s):  
Sound Absorption ◽  
Woven Fabrics ◽  
Absorption Coefficients ◽  
Basic Study ◽  
Low Frequencies ◽  
Permeable Membrane ◽  
High Frequencies ◽  
Single Leaf ◽  
A Value ◽  
Plane Space

In this communication, the sound absorption characteristics of rectangular-shaped plane space sound absorbers without any backing structure using permeable membranes (PMs) are measured by reverberation room method. First, three types of PMs, in this study woven fabrics, are selected with different flow resistances and surface densities. They are prepared in the plane rectangular-shaped space absorbers of two different sizes. The measured results are discussed through comparison with the existing theoretical and measured results for absorbers of the other shapes or configurations. The present results and discussion demonstrate that the reverberation absorption coefficients of the proposed absorbers are low at low frequencies and converge to a moderately high value at high frequencies. Especially, ones with higher flow resistance than the air impedance converge to a value greater than 0.5, which is a theoretically estimated maximum absorption coefficient of infinite single-leaf PM. This is inferred to be attributed mainly to area effect. From these results the proposed absorbers can be used effectively despite of their very simple structure. Also it is found that the proposed absorber can offer higher sound absorption than permeable membrane absorbers of other shapes or configuration. Regarding the effect of the size, the absorbers of smaller size offer higher absorption coefficients regardless of material properties of the PMs used in the experiments.

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