A nanofibrous acoustic system based on the cavity/membrane resonance principle

Room acoustic solutions are based on measurements of the acoustic power of the room and acoustic elements with different functions (absorption tiles, absorption ceilings, absorption bodies, diffusers, barriers). This work is focused only on absorption elements, with an emphasis on addressing lower frequencies. The goal of this research is achieved by sound absorbing means which contains a cavity resonator with a nanofibrous resonant membrane, which overlaps orifices of the cavity resonator. The design of the material is based on broadband noise. Absorption of lower frequencies is restricted to a certain extent by the final thickness of the acoustic material. A two-microphone impedance tube for determining the sound absorption coefficient was used to measure the limited frequency spectrum 100–1600 Hz. These frequencies, however, cover the area particularly focusing on middle and lower frequencies. The principle of the acoustic system consists in using combination of a cavity resonator, by which the air or other material contained in its cavities is forced into vibration upon impact of sound waves of high frequency, and a nanofibrous resonant membrane, which is forced into vibration upon impact of sound waves of low frequency. The optimal arrangement of holes inside the perforated plate, according to broadband sound absorption, has been found.

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Sound absorptive light comprising nanofibrous resonant membrane applicable in room acoustics

Building Services Engineering Research and Technology ◽

10.1177/0143624417733404 ◽

2017 ◽

Vol 39 (3) ◽

pp. 362-370 ◽

Cited By ~ 2

Author(s):

Klara Kalinova

Keyword(s):

Broad Band ◽

Low Frequency ◽

Acoustic Power ◽

Acoustic Properties ◽

Room Acoustics ◽

Sound Waves ◽

Final Thickness ◽

Low Frequencies ◽

Perforated Sheet ◽

Lower Frequencies

Room acoustic solutions are based on measurements of the acoustic power of the room and acoustic elements with different functions (absorption tiles, absorption ceilings, absorption bodies, diffusers, barriers). This work is focused only on absorption elements with an emphasis on addressing lower-middle frequencies. The design of the material is based on broad band noise. Damping of lower frequencies is restricted to a certain extent by the final thickness of the acoustic material. Nanofibrous resonant membranes will be used in the design to achieve higher sound absorption at lower frequencies in comparison with commercially available materials. The principle of the acoustic system is to use combination of a perforated sheet covered by a nanofibrous resonant membrane, which is brought into forced vibration upon impact of sound waves of low frequency. Practical application:To absorb sounds of high frequencies, porous materials are used. To absorb sounds of low frequencies, resonant membranes are employed. However, these structures absorb only sounds of certain frequency. Nanofibrous layers have unique acoustic properties due to the large specific surface area of the nanofibres, where viscous losses may occur, and also the ability to resonate at its own frequency. The advantage of this technology is the space between the acoustic element with a thickness of 1–2 mm and the wall/ceiling, which can be used for the installation of lighting/audio speakers, etc. The acoustic light prototype has been made.

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Bilayer ventilated labyrinthine metasurfaces with high sound absorption and tunable bandwidth

Scientific Reports ◽

10.1038/s41598-021-84986-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jiayuan Du ◽

Yuezhou Luo ◽

Xinyu Zhao ◽

Xiaodong Sun ◽

Yanan Song ◽

...

Keyword(s):

Sound Absorption ◽

Air Flow ◽

Single Layer ◽

Sound Waves ◽

Acoustic Metamaterials ◽

Sound Barrier ◽

Free Air ◽

Relative Bandwidth ◽

Wide Range ◽

High Sound

AbstractThe recent advent of acoustic metamaterials offers unprecedented opportunities for sound controlling in various occasions, whereas it remains a challenge to attain broadband high sound absorption and free air flow simultaneously. Here, we demonstrated, both theoretically and experimentally, that this problem can be overcome by using a bilayer ventilated labyrinthine metasurface. By altering the spacing between two constituent single-layer metasurfaces and adopting asymmetric losses in them, near-perfect (98.6%) absorption is achieved at resonant frequency for sound waves incident from the front. The relative bandwidth of absorption peak can be tuned in a wide range (from 12% to 80%) by adjusting the open area ratio of the structure. For sound waves from the back, the bilayer metasurface still serves as a sound barrier with low transmission. Our results present a strategy to realize high sound absorption and free air flow simultaneously, and could find applications in building acoustics and noise remediation.

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Non-Wovens as Sound Reducers

Latvian Journal of Physics and Technical Sciences ◽

10.2478/lpts-2018-0014 ◽

2018 ◽

Vol 55 (2) ◽

pp. 64-76

Author(s):

D. Belakova ◽

A. Seile ◽

S. Kukle ◽

T. Plamus

Keyword(s):

Absorption Coefficient ◽

Surface Density ◽

Sound Absorption ◽

Transmission Loss ◽

Sound Transmission ◽

Sound Insulation ◽

Material Structure ◽

Sound Transmission Loss ◽

Sound Waves ◽

Frequency Range

Abstract Within the present study, the effect of hemp (40 wt%) and polyactide (60 wt%), non-woven surface density, thickness and number of fibre web layers on the sound absorption coefficient and the sound transmission loss in the frequency range from 50 to 5000 Hz is analysed. The sound insulation properties of the experimental samples have been determined, compared to the ones in practical use, and the possible use of material has been defined. Non-woven materials are ideally suited for use in acoustic insulation products because the arrangement of fibres produces a porous material structure, which leads to a greater interaction between sound waves and fibre structure. Of all the tested samples (A, B and D), the non-woven variant B exceeded the surface density of sample A by 1.22 times and 1.15 times that of sample D. By placing non-wovens one above the other in 2 layers, it is possible to increase the absorption coefficient of the material, which depending on the frequency corresponds to C, D, and E sound absorption classes. Sample A demonstrates the best sound absorption of all the three samples in the frequency range from 250 to 2000 Hz. In the test frequency range from 50 to 5000 Hz, the sound transmission loss varies from 0.76 (Sample D at 63 Hz) to 3.90 (Sample B at 5000 Hz).

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EFFECT OF POROUS STRUCTURE ON SOUND ABSORPTION OF CELLULAR CONCRETE

Construction Materials and Products ◽

10.34031/2618-7183-2020-3-2-5-18 ◽

2020 ◽

Vol 3 (2) ◽

pp. 5-18 ◽

Cited By ~ 2

Author(s):

R.S. Fedyuk ◽

A. Baranov ◽

Y.H. Mugahed Amran

Keyword(s):

Open Porosity ◽

Sound Absorption ◽

Concrete Mixture ◽

Sound Waves ◽

Foam Concrete ◽

Mechanical Adhesion ◽

The Matrix ◽

Reduce Shear Stress ◽

The Mathematical Model ◽

Cellular Concrete

the compositions of gas and foam concrete with improved acoustic characteristics were developed. The optimal form of porosity, which contributes to the absorption of sound waves, both in the range of audible frequencies and at infrasonic and ultrasonic frequencies, is revealed. The mathematical model for designing sound-absorbing concrete was improved, taking into account both the porosity of the composite and the influence of the porous aggregate. The laws of synthesis of aerated concrete and foam concrete are established, which consist in optimizing the processes of structure formation due to the use of a polymineral cement-ash binder and blowing agent. The composition of the composite intensifies the process of hydration of the system, which leads to the synthesis of a polymineral heterodisperse matrix with an open porosity of more than 60%. Peculiarities of the influence of the “Portland cement – aluminosilicate – complex of modifiers” system on the rheology of the concrete mixture was identified, which can significantly reduce shear stress and create easily formed cellular concrete mixtures. The increased activity and granulometry of aluminosilicates predetermine an increase in the number of contacts and mechanical adhesion between particles during compaction, strengthening the frame of inter-pore septa. The mechanism of the influence of the composition of the concrete mixture on the microstructure of the composite is established. The presence of refined aluminosilicates and a complex of additives in the system along with cement contribute to the synthesis of the matrix with open porosity, thereby increasing the sound absorption coefficient.

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Estimation and experimental test of the sound-absorption coefficient of a pin-holder structure (Case of sound waves incidence upon the side surfaces of a group of cylinders)

INTER-NOISE and NOISE-CON Congress and Conference Proceedings ◽

10.3397/in-2021-2497 ◽

2021 ◽

Vol 263 (3) ◽

pp. 3714-3719

Author(s):

Takamasa Sato ◽

Shuichi Sakamoto ◽

Isami Nitta ◽

Shunsuke Unai ◽

Takunari Isobe ◽

...

Keyword(s):

Absorption Coefficient ◽

Sound Absorption ◽

Propagation Constant ◽

Characteristic Impedance ◽

Physical Property ◽

Sound Absorption Coefficient ◽

Accurate Estimation ◽

Sound Waves ◽

Acoustic Characteristics ◽

Measuring Tube

In this study, we conducted theoretical analyses and experiments related to the acoustic characteristics of the situation where sound waves are incident upon the side surfaces of a group of cylinders forming a pin-holder structure. The sound-absorption coefficient, entering its clearance between cylinders through the geometrical dimension of the clearance or the physical property of gas, was calculated. In the analytical model, the gap part of the pin-holder structure was divided into elements and approximated as a gap surrounded by two parallel planes. The characteristic impedance and propagation constant of the approximate gap were obtained and treated as one-dimensional transfer matrices; the sound-absorption coefficient was then calculated using the transfer-matrix method. The calculated value was compared to that obtained in an experiment with a sample prepared using a 3D printer; the sound-absorption coefficient was measured using a 2-microphone impedance-measuring tube. We attempted to make a simple yet accurate estimation of sound-absorption coefficient using these procedures. Our theoretical values displayed a similar tendency to that obtained by experiment.

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Prediction of Sound Absorption of Stacked Granular Materials for Normal and Oblique Incident Sound Waves

Acta Acustica united with Acustica ◽

10.3813/aaa.919189 ◽

2018 ◽

Vol 104 (3) ◽

pp. 464-476 ◽

Cited By ~ 1

Author(s):

M. Bezemer-Krijnen ◽

Y. H. Wijnant ◽

A. de Boer

Keyword(s):

Granular Materials ◽

Sound Absorption ◽

Sound Waves

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SeMSA: a compact super absorber optimised for broadband, low-frequency noise attenuation

Scientific Reports ◽

10.1038/s41598-020-73933-0 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Andrew McKay ◽

Ian Davis ◽

Jack Killeen ◽

Gareth J. Bennett

Keyword(s):

New Technology ◽

Perforated Plate ◽

Low Frequency ◽

Broadband Noise ◽

Frequency Noise ◽

Noise Attenuation ◽

Loss Mechanism ◽

Small Form Factor ◽

Broadband Sound ◽

Sub Wavelength

Abstract The attenuation of low-frequency broadband noise in a light, small form-factor is an intractable challenge. In this paper, a new technology is presented which employs the highly efficient visco-thermal loss mechanism of a micro-perforated plate (MPP) and successfully lowers its frequency response by combining it with decorated membrane resonators (DMR). Absorption comes from the membranes but primarily from the MPP, as the motion of the two membranes causes a pressure differential across the MPP creating airflow through the perforations. This combination of DMR and MPP has led to the Segmented Membrane Sound Absorber (SeMSA) design, which is extremely effective at low-frequency broadband sound absorption and which can achieve this at deep sub-wavelength thicknesses. The technology is compared to other absorbers to be found in the literature and the SeMSA outperforms them all in either the 20–1000 Hz or 20–1200 Hz range for depths of up to 120 mm. This was verified through analytical, finite element and experimental analyses.

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Broadening of the Sound Absorption Bandwidth of the Perforated Panel Using a Membrane-Type Resonator

Journal of Vibration and Acoustics ◽

10.1115/1.4038942 ◽

2018 ◽

Vol 140 (3) ◽

Cited By ~ 4

Author(s):

Xuezhi Zhu ◽

Zhaobo Chen ◽

Yinghou Jiao ◽

Yanpeng Wang

Keyword(s):

Absorption Coefficient ◽

Sound Absorption ◽

Degrees Of Freedom ◽

Low Frequency ◽

Absorption Capacity ◽

Sound Absorption Coefficient ◽

Sound Waves ◽

Frequency Range ◽

Absorption Bandwidth ◽

Membrane Type

In order to broaden the sound absorption bandwidth of a perforated panel in the low frequency range, a lightweight membrane-type resonator is installed in the back cavity of the perforated panel to combine into a compound sound absorber (CSA). Because of the great flexibility, the membrane-type resonator can be vibrated easily by the incident sound waves passing through the holes of the perforated panel. In the low frequency range, the membrane-type resonator and the perforated panel constitute a two degrees-of-freedom (DOF)-resonant type sound absorption system, which generates two sound absorption peaks. By tuning the parameters of the membrane type resonator, a wide frequency band having a large sound absorption coefficient can be obtained. In this paper, the sound absorption coefficient of CSA is derived analytically by combining the vibration equation of the membrane-type resonator with the acoustic impedance equation of the perforated panel. The influences of the parameters of the membrane-type resonator on the sound absorption performance of the CSA are numerically analyzed. Finally, the wide band sound absorption capacity of the CSA is validated by the experimental test.

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A Preliminary Study on the Sound Absorption of Self-Facing Date Palm Fibers

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.565.25 ◽

2014 ◽

Vol 565 ◽

pp. 25-30 ◽

Cited By ~ 1

Author(s):

Elwaleed A. Khidir ◽

N. Nikabdullah ◽

M.J.M. Nor ◽

M.F.Mat Tahir ◽

M.Z. Nuawi

Keyword(s):

Sound Absorption ◽

Date Palm ◽

Perforated Plate ◽

Low Frequency ◽

Single Layer ◽

Absorption Properties ◽

Date Palm Fibers ◽

Layer Sample ◽

Good Improvement ◽

Preliminary Study

Sound absorption of self-facing natural date palm fibershas been investigated.A single layer sample of the fibers was tested for its sound absorption properties. The sample was then faced with the originally date palm fiber netted structure. Experimental measurements were conducted on the impedance tube at the acoustic lab, Faculty of Engineering, UniversitiKebangsaan Malaysia, to determine the sound absorption coefficient.The single layer was also tested using an aluminum perforated plate, as facing, for comparison purposes.The results show a good improvement in the sound absorption for the self-facing panel for the whole frequency range. However, when using the aluminum perforated panel an improvement in the sound absorption was observed only above 2500 Hz. The effect of introducing air gap thickness was studied. The results show improvement for the sound absorption the low frequency.

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