A Comparative Study on Sound Transmission Loss and Absorption Coefficient of Acoustical Materials

2011 ◽  
Author(s):  
John G. Cherng ◽  
Qian Xi ◽  
Pravansu Mohanty ◽  
Gordon Ebbitt
Keyword(s):  
Absorption Coefficient ◽  
Comparative Study ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Sound Transmission Loss

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).

A study on the effects of compression of the felt on flow resistance and acoustic characteristics

2021 ◽  
Vol 263 (1) ◽  
pp. 5170-5174
Author(s):  
Yoon-sang Yang ◽  
Seung Lee
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Flow Resistance ◽  
Transmission Loss ◽  
Combustion Engine ◽  
Characteristic Impedance ◽  
Sound Transmission ◽  
Sound Absorption Coefficient ◽  
Sound Transmission Loss ◽  
Acoustic Characteristics

The sound absorbing materials used to reduce automobile interior noise are classified into Felt and PU Foam. Felt are widely used not only in internal combustion engine vehicles but also in Electric Vehicles because they are eco-friendly materials that can be recycled and relatively light. Automotive interior parts manufacture materials in various thicknesses depending on the shape of matched parts. The pressed material changes the density, flow resistance and affects the overall NVH performance of the vehicle. In this study we worked to confirm changes in flow resistance, sound absorption coefficient and sound transmission loss performance among acoustic characteristics based on the compress ratio of Felt. It was confirmed that the larger the compression of Felt, the larger the flow resistance value, thereby affecting the acoustic characteristic impedance, sound absorption coefficient and sound transmission loss.

Sound insulation analysis of micro-perforated panel coupled with honeycomb panel considering air cavity for offshore plants

2018 ◽  
Vol 233 (4) ◽  
pp. 1037-1055 ◽  
Author(s):  
Jae-Deok Jung ◽  
Suk-Yoon Hong ◽  
Jee-Hun Song ◽  
Hyun-Wung Kwon
Keyword(s):  
Absorption Coefficient ◽  
Transmission Loss ◽  
Perforated Plate ◽  
Sound Transmission ◽  
Sound Insulation ◽  
Sound Transmission Loss ◽  
The Face ◽  
Plate Perforation ◽  
Offshore Plants ◽  
Honeycomb Panel

The wall panels used in offshore plants require sound insulation performance as well as fireproofing. A honeycomb panel made of metal is incombustible but unsatisfactory at the middle frequencies for sound transmission loss because the coincidence frequency occurs when the bending wavelength on the panel matches the wavelength of the incident wave. In this study, the application of a micro-perforated plate to the honeycomb panel was considered to supplement the sound transmission loss at the middle frequencies. The honeycomb core was assumed to overlap an orthotropic layer with an air layer, and face sheets were assumed to be isotropic. The kinetic and potential energy for the face sheets and the honeycomb core, the kinetic energy for the air layer located between the face sheets, and the sound absorption coefficient for the panel were derived. These were substituted into the Lagrange equation, and by solving the equation, the sound transmission loss was obtained. By comparing the experimental results with theoretically predicted results, it was found that the theory well reflected the measured surface density, elasticity, and absorption coefficient. Finally, simulations were performed for the micro-perforated plate perforation presence, micro-perforated plate perforation diameter, cell wall thickness, and cell size. These were analyzed with regard to the surface density, elasticity, and absorption coefficient.

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