scholarly journals Development and Investigation of Fully Ventilated Deep Subwavelength Absorbers

Symmetry ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1835
Author(s):  
Heng Wang ◽  
Qibo Mao
Keyword(s):  
Theoretical Model ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Acoustic Metamaterial ◽  
Acoustic Performance ◽  
Half Wave ◽  
Quarter Wave ◽  
New Type ◽  
Good Agreement

A new type of deep subwavelength acoustic metamaterial (AMM) absorber with 100% ventilation is presented in this study. The proposed ventilation absorber consists of coiled-up half-wave resonators (HWRs) and quarter-wave resonators (QWRs). First, the sound absorption and sound transmission performances for absorbers were analyzed considering the thermal viscosity dissipation. Then, the prototype with ten HWRs and three QWRs composed of acrylic plates was manufactured based on the theoretical model. The acoustic performance of the absorber was tested in an air-filled acoustic impedance tube to determine the sound absorption and transmission loss performances. Good agreement was found between the measured and theoretically predicted results. The experimental results show that the proposed ventilation AMM absorber is able to achieve sound absorption in a range between 330 Hz and 460 Hz with a thickness of only 32 mm (about 3% of the wavelength in the air). Furthermore, the sound transmission loss can achieve 17 dB from 330 Hz to 460 Hz. The main advantage of the proposed absorber is that it can be completely ventilated in duct noise control.

scholarly journals Non-Wovens as Sound Reducers

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).

Compact filtering power dividers with wide upper stopband

2019 ◽  
Vol 11 (08) ◽  
pp. 765-773
Author(s):  
Gaoya Dong ◽  
Weimin Wang ◽  
Yuanan Liu
Keyword(s):  
Transmission Lines ◽  
Wave Transmission ◽  
Coupling Matrix ◽  
Power Dividers ◽  
Full Wave ◽  
Half Wave ◽  
Coupled Lines ◽  
Quarter Wave ◽  
Simulation Results ◽  
Good Agreement

AbstractA series of compact filtering power dividers (FPDs) with simple layouts are proposed based on coupling topology. The structure of the presented FPD1 is composed of three resonators and one isolating resistor. These FPDs can be designed based on coupling matrix filter theory. A half-wave transmission line is employed in FPD2 to introduce a transmission zero (TZ) locating at 1.27f0. The FPD3 is designed by replacing quarter-wave transmission lines in FPD2 with quarter-wave coupled lines, which will produce a TZ locating at 1.96 f0 and extend upper stopband bandwidth. For verification, three FPDs centered at 2.45 GHz are fabricated and measured. All measured results are in good agreement with the full-wave simulation results.

scholarly journals High sound absorption of polyester composites / fiber hemp / nanocellulose for automotive interior materials

2020 ◽  
Vol 2 (2) ◽  
pp. 170-174
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Sound Absorption ◽  
Natural Fiber ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Sound Transmission Loss ◽  
Hemp Fiber ◽  
The Matrix ◽  
Polyester Composite

Human health and environmental comfort are disturbed by the presence of noise, especially in cars, so that effective sound-absorbing materials are currently being developed. To answer the problem of noise in car interiors, polyester composite materials with local hemp fiber and nanocellulose reinforcement were developed. Natural fiber is biodegradable and renewable, and acts as an alternative to the use of synthetic fibers. The method used for the composite material manufacturing process was the casting method. The matrix of the composite material was polyester, while the reinforcement was a combination of local hemp fiber and nanocellulose fiber. Alkalization and non-alkalization processes have been carried out on hemp fiber. The composition of nanocellulose was 0%, 1%, and 3%. The characterization applied in this research were SEM test, FTIR test, sound transmission loss test, and density test. Optimal results were obtained on hemp fiber reinforced polyester composite materials without alkalization and without nanocellulose. Sound transmission loss (STL) was 61.91 dB up to 68.52 dB for the frequency range of 630 Hz to 125 Hz. The standard noise limit on 8-passenger passenger's four-wheeled vehicles is 77-80 dB. Based on the results obtained, the sound absorption is good. The density of this composite material was obtained at 0.989 gram/cm3. This composite material has the potential for developing dashboard material.

An improved approach for normal-incidence sound transmission loss measurement using a four-microphone impedance tube

2020 ◽  
pp. 107754632092690
Author(s):  
Zechao Li ◽  
Sizhong Chen ◽  
Zhicheng Wu ◽  
Lin Yang
Keyword(s):  
Transfer Matrix ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Normal Incidence ◽  
Sound Insulation ◽  
Sound Transmission Loss ◽  
The Common ◽  
Wavefield Decomposition ◽  
Insulation Performance

The main aim of this study is to introduce an improved method for determining the sound properties of acoustic materials which is more precise than the common wavefield decomposition method and simpler than the common transfer matrix method. In the first part of the article, a group of formulae for calculating sound transmission loss is represented by combining the wavefield decomposition and transfer matrix methods. Subsequently, a formula for calculating sound absorption coefficients is derived from these formulae by definition. Furthermore, the present formulae are validated by comparing the experimental results achieved with the present formulae and those results obtained by other methods recorded in published articles. Eventually, it is demonstrated that the method can accurately measure the sound insulation performance of materials and the sound absorption properties of limp and lightweight materials.

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