scholarly journals EXPERIMENTAL INVESTIGATION OF AN ACOUSTIC METAMATERIAL BARRIER DESIGN COMPOSED OF A SQUARE PRISM WITHIN A HEXAGONAL RECESS

2021 ◽  
Vol 11 (3) ◽  
pp. 57-70
Author(s):  
Luo Mu ◽  
Zamir Aimaduddin Zulkefli ◽  
Nawal Aswan Abdul Jalil ◽  
Azma Putra ◽  
Muhammad Nur Othman ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Absorption Coefficient ◽  
Transmission Loss ◽  
Stop Band ◽  
Unit Cell ◽  
Acoustic Absorption ◽  
Acoustic Metamaterial ◽  
Square Prism ◽  
Peak Transmission ◽  
Single Material

This paper presents an experimental investigation of an acoustic barrier composed out of an acousticmetamaterial unit cell. The design of the unit cell consists of a square prism, acting as a resonator,within a hexagonal recess manufactured out of a single material. Two materials were used tomanufacture the unit cell: PolyMide Polycarbonate and Polylite Polylactic Acid. The acousticperformance of the unit cell was quantified for both materials using the acoustic absorptioncoefficient and acoustic transmission loss values for frequencies between 100 Hz and 5,000Hz. Theexperimental results indicate that the design reduced the peak absorption coefficient for bothmaterials while also introducing two additional peaks at around 1,500 Hz and at 4,000 Hz. Changesto the absorption coefficient values were observed for frequencies above 1,000 Hz while minimalchanges were observed for frequencies below 1,000 Hz. These results indicate that the proposeddesign, is able to widen the effective frequency band, or stop band for acoustic absorption forfrequencies above 1,000 Hz compared to the absorption coefficient of the material. The experimentalresults also indicate that the design increases the peak transmission loss by about 7 dB at 4,000 Hz.For sounds below 3,000 Hz, the design will only change the transmission loss by about 3 dB forfrequencies between 100 Hz to 3,000 Hz. These results indicate that the acoustic metamaterial design,consisting of resonator in a recess manufactured out of a single material, is able to broaden theeffective frequency range for sound absorption for frequencies between 1,000 Hz and 4,000 Hz andat increasing the transmission loss values for frequencies between 3,000 Hz and 5,000 Hz. It can beconcluded that the resonator in recess metamaterial design, manufactured out of a single material,can be used to increase the stop band for acoustic absorption for frequencies above 1,000 Hz and toincrease the transmission loss for frequencies above 3,000 Hz.

Low-frequency sound absorption of a tunable multilayer composite structure

2021 ◽  
pp. 107754632110082
Author(s):  
Hanbo Shao ◽  
Jincheng He ◽  
Jiang Zhu ◽  
Guoping Chen ◽  
Huan He
Keyword(s):  
Porous Material ◽  
Absorption Coefficient ◽  
Composite Structure ◽  
Low Frequency ◽  
Acoustic Absorption ◽  
Multilayer Composite ◽  
Absorption Frequency ◽  
Acoustic Absorption Coefficient ◽  
Simulation And Experiment ◽  
Single Material

Our work investigates a tunable multilayer composite structure for applications in the area of low-frequency absorption. This acoustic device is comprised of three layers, Helmholtz cavity layer, microperforated panel layer, and the porous material layer. For the simulation and experiment in our research, the absorber can fulfill a twofold requirement: the acoustic absorption coefficient can reach near 0.8 in very low frequency (400 Hz) and the range of frequency is very wide (400–3000 Hz). In all its absorption frequency, the average of the acoustic absorption coefficient is over 0.9. Besides, the absorption coefficient can be tunable by the scalable cavity. The multilayer composite structure in our article solved the disadvantages in single material. For example, small absorption coefficient in low frequency in traditional material such as microperforated panel and porous material and narrow reduction frequency range in acoustic metamaterial such as Helmholtz cavity. The design of the composite structure in our article can have more wide application than single material. It can also give us a novel idea to produce new acoustic devices.

scholarly journals The Effects of Various Additive Components on the Sound Absorption Performances of Polyurethane Foams

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Shuming Chen ◽  
Yang Jiang ◽  
Jing Chen ◽  
Dengfeng Wang
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Polyurethane Foams ◽  
Acoustic Properties ◽  
Acoustic Absorption ◽  
Absorption Properties ◽  
Maximum Enhancement ◽  
Flexible Polyurethane ◽  
Pu Foams

Flexible polyurethane (PU) foams comprising various additive components were synthesized to improve their acoustic performances. The purpose of this study was to investigate the effects of various additive components of the PU foams on the resultant sound absorption, which was characterized by the impedance tube technique to obtain the incident sound absorption coefficient and transmission loss. The maximum enhancement in the acoustic properties of the foams was obtained by adding fluorine-dichloroethane (141b) and triethanolamine. The results showed that the acoustic absorption properties of the PU foams were improved by adding 141b and triethanolamine and depended on the amount of the water, 141b, and triethanolamine.

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).

scholarly journals Kajian Eksperimental Koefisien Redaman Akustik Bahan Pelapis Plat Dek Kapal

2018 ◽  
Vol 3 (1) ◽  
pp. 41
Author(s):  
Wibowo Harso Nugroho ◽  
Nanang J.H. Purnomo ◽  
Hardi Zen ◽  
Andi Rahmadiansah
Keyword(s):  
Absorption Coefficient ◽  
High Frequency ◽  
Transmission Loss ◽  
Base Material ◽  
Sound Insulation ◽  
Insulation Material ◽  
Base Materials ◽  
Specimen Material ◽  
Ship Classification ◽  
Technical Assessment

With the increasingly strict requirements of the ship classification bureau for permissible noise limits to allow passengers and crew to be more comfortable and secure a technical assessment is required to address the characteristics of the noise. A noise beyond the standard allowed in the vessel can be a problem to the ship operators. This noise problem will greatly affects the crews' comfort and passengers. One method to reduce the noise on a ship is to use sound insulation. This paper describes the method for determining the absorption coefficient α and the transmission loss (TL) through an acoustic test of a concrete insulation in the laboratory. The test was conducted by using the method of impedance tube where a speciment response measured by a microphone. In general, the properties of this insulation material remains as the main base material which is concrete. it has been found that the transmission loss value (TL) is in the range of 10 - 50 dB whereas for the base material the concrete is around 22 - 49 dB but the absorption coefficient α of the specimen material is much higher than the material of the base material especially in high frequency, which ranges from 0.15 to 0.97, whereas for concrete base materials have absorbent coefficient α ranges from 0.01 to 0.02.

scholarly journals Comparasion of prediction and measurement methods for sound insulation of lightweight partitions

2012 ◽  
Vol 10 (2) ◽  
pp. 155-167 ◽  
Author(s):  
Momir Prascevic ◽  
Dragan Cvetkovic ◽  
Darko Mihajlov
Keyword(s):  
Transmission Loss ◽  
Road Traffic ◽  
Theoretical Models ◽  
Measurement Methods ◽  
Experimental Results ◽  
Sound Insulation ◽  
Acoustic Absorption ◽  
Noise Levels ◽  
Overall Design ◽  
Acoustic Comfort

It is important to know the sound insulation of partitions in order to be able to compare different constructions, calculate acoustic comfort in apartments or noise levels from outdoor sources such as road traffic, and find engineer optimum solutions to noise problems. The use of lightweight partitions as party walls between dwellings has become common because sound insulation requirements can be achieved with low overall surface weights. However, they need greater skill to design and construct, because the overall design is much more complex. It is also more difficult to predict and measure of sound transmission loss of lightweight partitions. There are various methods for predicting and measuring sound insulation of partitions and some of them will be described in this paper. Also, this paper presents a comparison of experimental results of the sound insulation of lightweight partitions with results obtained using different theoretical models for single homogenous panels and double panels with and without acoustic absorption in the cavity between the panels.

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