Sound absorption characteristics of multilayer porous metal materials backed with an air gap

2014 ◽  
Vol 22 (12) ◽  
pp. 2861-2872 ◽  
Author(s):  
Ning JingFeng ◽  
Zhao GuiPing
Keyword(s):  
Sound Absorption ◽  
Porous Metal ◽  
Air Gap ◽  
Metal Materials ◽  
Absorption Characteristics

scholarly journals Elucidating the Sound Absorption Characteristics of Foxtail Millet (Setariaitalica) Husk

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5126
Author(s):  
Dhayalini Balasubramanian ◽  
Senthil Rajendran ◽  
Bhuvanesh Srinivasan ◽  
Nirmalakumari Angamuthu
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Foxtail Millet ◽  
Air Gap ◽  
Composite Panel ◽  
Sound Absorption Coefficient ◽  
Mass Content ◽  
Frequency Range ◽  
Backing Material ◽  
Absorption Characteristics

The current study deals with the analysis of sound absorption characteristics of foxtail millet husk powder. Noise is one the most persistent pollutants which has to be dealt seriously. Foxtail millet is a small seeded cereal cultivated across the world and its husk is less explored for its utilization in polymer composites. The husk is the outer protective covering of the seed, rich in silica and lingo-cellulose content making it suitable for sound insulation. The acoustic characterization is done for treated foxtail millet husk powder and polypropylene composite panels. The physical parameters like fiber mass content, density, and thickness of the composite panel were varied and their influence over sound absorption was mapped. The influence of porosity, airflow resistance, and tortuosity was also studied. The experimental result shows that 30-mm thick foxtail millet husk powder composite panel with 40% fiber mass content, 320 kg/m3 density showed promising sound absorption for sound frequency range above 1000 Hz. We achieved noise reduction coefficient (NRC) value of 0.54. In view to improve the performance of the panel in low-frequency range, we studied the efficiency of incorporating air gap and rigid backing material to the designed panel. We used foxtail millet husk powder panel of density 850 kg/m3 as rigid backing material with varying air gap thickness. Thus the composite of 320 kg/m3 density, 30-mm thick when provided with 35-mm air gap and backing material improved the composite’s performance in sound frequency range 250 Hz to 1000 Hz. The overall sound absorption performance was improved and the NRC value and average sound absorption coefficient (SAC) were increased to 0.7 and 0.63 respectively comparable with the commercial acoustic panels made out of the synthetic fibers. We have calculated the sound absorption coefficient values using Delany and Bezlay model (D&B model) and Johnson–Champoux–Allard model (JCA model) and compared them with the measured sound absorption values.

Double Perforated Honeycomb Panel as a Low Frequency Acoustic Absorber

1997 ◽  
Vol 4 (1) ◽  
pp. 21-37
Author(s):  
C.F. Ng ◽  
Qin Hao-Ming
Keyword(s):  
Experimental Study ◽  
Sound Absorption ◽  
Low Frequency ◽  
Air Gap ◽  
Light Weight ◽  
Frequency Sound ◽  
Honeycomb Sandwich ◽  
Perforated Sheets ◽  
Absorption Characteristics ◽  
Honeycomb Panel

This report deals with a theoretical and experimental study of the low frequency sound absorption characteristics of perforated honeycomb sandwich panels. The derivations of formulae for absorption in terms of double perforation ratio and air gap are presented. Results show that the honeycomb absorber, with double perforated sheets, can be an effective low frequency absorber for frequencies down to 63 Hz. In addition, honeycomb panels have advantages over other low frequency absorbers in that they are light weight and strong.

Sound Absorption Characteristics and Structure Optimization of Porous Metal Fibrous Materials

2015 ◽  
Vol 44 (11) ◽  
pp. 2646-2650 ◽  
Author(s):  
Ao Qingbo ◽  
Wang Jianzhong ◽  
Tang Huiping ◽  
Zhi Hao ◽  
Ma Jun ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Structure Optimization ◽  
Porous Metal ◽  
Fibrous Materials ◽  
Absorption Characteristics

scholarly journals Sound absorption characteristics of a double-leaf structure with an MPP and a permeable membrane

2014 ◽  
Vol 76 ◽  
pp. 28-34 ◽  
Author(s):  
Kimihiro Sakagami ◽  
Yusaku Fukutani ◽  
Motoki Yairi ◽  
Masayuki Morimoto
Keyword(s):  
Sound Absorption ◽  
Leaf Structure ◽  
Permeable Membrane ◽  
Absorption Characteristics

Trial applications at gymnasiums of in-situ sound absorption measurement method by ensemble averaging technique

2021 ◽  
Vol 263 (2) ◽  
pp. 4532-4537
Author(s):  
Toru Otsuru ◽  
Reiji Tomiku ◽  
Noriko Okamoto ◽  
Siwat Lawanwadeekul
Keyword(s):  
Measurement Method ◽  
Sound Absorption ◽  
Glass Wool ◽  
Absorption Measurement ◽  
Ensemble Averaging ◽  
Averaging Technique ◽  
In Situ Conditions ◽  
Measurement Consistency ◽  
Absorption Characteristics

The authors have been published a series of papers on a measurement method for sound absorption characteristics of materials using ensemble averaging technique, i.e., EA method. The papers' results included measurement mechanisms, measurement uncertainty, and so on. Herein, to examine adaptability, especially in in-situ conditions, the EA method is applied to measure absorption characteristics of materials installed in two gymnasiums. A glass-wool panel with the dimension of 0.5 m by 0.5 m by 0.05 m and with the density of 32 kg m^-3 was brought around and measured to check the measurement consistency. Several measurements were conducted during badminton plays were undergoing. Measured sound absorption coefficients revealed that most results agree well with those measured in reverberation rooms. Certain improvement is necessary for the specimen brought to the in-situ measurement to keep the consistency. The inconsistency is considered to originate from unstable conditions between the specimen and floor.

scholarly journals Preparation and Characterization of Gradient Compressed Porous Metal for High-Efficiency and Thin-Thickness Acoustic Absorber

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1413 ◽  
Author(s):  
Xiaocui Yang ◽  
Xinmin Shen ◽  
Panfeng Bai ◽  
Xiaohui He ◽  
Xiaonan Zhang ◽  
...  
Keyword(s):  
Sound Absorption ◽  
High Efficiency ◽  
Structural Parameters ◽  
Porous Metal ◽  
Theoretical Models ◽  
Absorption Efficiency ◽  
Total Thickness ◽  
Porous Metals ◽  
Absorption Coefficients ◽  
Optimal Average

Increasing absorption efficiency and decreasing total thickness of the acoustic absorber is favorable to promote its practical application. Four compressed porous metals with compression ratios of 0%, 30%, 60%, and 90% were prepared to assemble the four-layer gradient compressed porous metals, which aimed to develop the acoustic absorber with high-efficiency and thin thickness. Through deriving structural parameters of thickness, porosity, and static flow resistivity for the compressed porous metals, theoretical models of sound absorption coefficients of the gradient compressed porous metals were constructed through transfer matrix method according to the Johnson–Champoux–Allard model. Sound absorption coefficients of four-layer gradient compressed porous metals with the different permutations were theoretically analyzed and experimentally measured, and the optimal average sound absorption coefficient of 60.33% in 100–6000 Hz was obtained with the total thickness of 11 mm. Sound absorption coefficients of the optimal gradient compressed porous metal were further compared with those of the simple superposed compressed porous metal, which proved that the former could obtain higher absorption efficiency with thinner thickness and fewer materials. These phenomena were explored by morphology characterizations. The developed high-efficiency and thin-thickness acoustic absorber of gradient compressed porous metal can be applied in acoustic environmental detection and industrial noise reduction.

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