Study and estimation of sound absorption coefficient of pin holder structure

2021 ◽  
Vol 69 (2) ◽  
pp. 102-111
Author(s):  
Takamasa Satoh ◽  
Shuichi Sakamoto ◽  
Kohta Akamine ◽  
Shunsuke Unai ◽  
Takunari Isobe ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Absorption Coefficient ◽  
Transfer Matrix ◽  
Sound Absorption ◽  
Propagation Constant ◽  
Characteristic Impedance ◽  
Physical Property ◽  
Sound Absorption Coefficient ◽  
Accurate Estimation ◽  
Analysis Model

In this study, a theoretical analysis of the acoustic characteristics of a pin holder structure was conducted. In addition, the sound absorption coefficient, entering its clearance through the geometrical dimension of the clearance or the physical property of air, was calculated. The analysis model approximates the aperture of a pin holder structure as the clearance between two parallel surfaces. Thus, the propagation constant and characteristic impedance were obtained and treated as a one-dimensional transfer matrix. Subsequently, the sound absorption coefficient was calculated using the transfer matrix method and was compared with the experimental results. In the experiment, a two-microphone impedance tube was used to measure the sound absorption coefficient of the test samples. We attempted to perform a simple yet accurate estimation using these procedures. The theoretical analysis values exhibited a similar tendency to that of the experimental values.

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)

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.

Computation of the Alpha Cabin Sound Absorption Coefficient by Using the Finite Transfer Matrix Method (FTMM): Inter-Laboratory Test on Porous Media

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Andrea Santoni ◽  
Paolo Bonfiglio ◽  
Patrizio Fausti ◽  
Francesco Pompoli
Keyword(s):  
Absorption Coefficient ◽  
Transfer Matrix ◽  
Transfer Matrix Method ◽  
Matrix Method ◽  
Sound Absorption ◽  
Finite Size ◽  
Sound Absorption Coefficient ◽  
Radiation Impedance ◽  
Simulation Based ◽  
Private Research

Abstract The transfer matrix method (TMM) has become an established and widely used approach to compute the sound absorption coefficient of a multilayer structure. Due to the assumption made by this method of laterally infinite media, it is necessary to introduce in the computation the finite-size radiation impedance of the investigated system, in order to obtain an accurate prediction of the sound absorption coefficient within the entire frequency range of interest; this is generally referred to as finite transfer matrix method (FTMM). However, it has not been extensively investigated the possibility of using the FTMM to accurately approximate the sound absorption of flat porous samples experimentally determined in an Alpha Cabin, a small reverberation room employed in the automotive industry. To this purpose, a simulation-based round robin test was organized involving academic and private research groups. Four different systems constituted by five porous materials, whose properties were experimentally characterized, were considered. Each participant, provided with all the mechanical and physical properties of each medium, was requested to simulate the sound absorption coefficient with an arbitrary chosen code, based on the FTMM. The results indicated a good accuracy of the different formulations to determine the finite-size radiation impedance. However, its implementation in the computation of the sound absorption coefficient as well as the upper limit of the range of incidence angles within which the acoustic field is simulated, and the model adopted to describe each material, significantly influenced the results.

scholarly journals Design and simulation of multilayer hybrid foam material for acoustic application

2021 ◽  
Vol 12 ◽  
pp. 10
Author(s):  
L. Yuvaraj ◽  
S. Jeyanthi ◽  
Lenin Babu Mailan Chinnapandi ◽  
Elammaran Jayamani
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Noise Control ◽  
Numerical Study ◽  
Characteristic Impedance ◽  
Sound Absorption Coefficient ◽  
Metallic Foam ◽  
Polymeric Foam ◽  
Closed Cell ◽  
The Individual

New acoustic multilayer absorber fabricated by coupling closed-cell metallic foam and open-cell polymeric foam, which aimed to develop a practical use of metallic foam in the noise control application. In prior, the individual sound absorption coefficient of both foam materials with different thicknesses measured by the impedance tube method as per ASTM E-1050. Using inverse characterization technique, the intrinsic properties needed for five parameter models in a numerical study are predicted. The measured characteristic impedance, complex wave propagation, and sound absorption coefficient of the individual foams are in close agreement with the prediction. Subsequently, a different configuration of multilayer absorber is modeled using obtained properties, and their acoustic performance is evaluated. The result indicates that the coupling of polymeric foam with metallic one exhibits enhanced sound absorption and usage of closed-cell metallic foam in noise control material. Furthermore, the result demonstrates that absorption capability entirely relies on the placement of polymeric foam in the configuration. The proposed hybrid multilayer absorber coupled with test bench car for interior acoustic study, where 5–30 dB is reduction is noticed in 1/3rd octave plot.

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.

scholarly journals Effect of Diffusion Conditions on Absorption Performance of Materials Evaluated in Reverberation Chamber

2019 ◽  
Vol 11 (23) ◽  
pp. 6651
Author(s):  
Kyung Ho Kim ◽  
Jin Yong Jeon
Keyword(s):  
Absorption Coefficient ◽  
Edge Effect ◽  
Sound Absorption ◽  
Specimen Surface ◽  
Sound Absorption Coefficient ◽  
Accurate Estimation ◽  
Reverberation Chamber ◽  
Evaluation Indicator ◽  
Relative Standard ◽  
Absorption Performance

Obtaining the reverberation time of a multipurpose building is most effective when accurate data is used to simulate the building. Therefore, this study proposes a method of measuring the sound absorption coefficient that is close to the sound absorption performance of the conditions in which building materials are actually used. In addition, a sufficient diffusivity evaluation method for sound absorption coefficient measurement in a reverberation chamber is proposed, to address the sound absorption performance difference caused by internal diffusion of the reverberation chamber. When the sound absorption performance was evaluated after installing the specimen under the condition of minimized edge effect, the result obtained should closely match the sound absorption performance of the specimen surface. The sound absorption performance of the specimen ( α β E ≈ 0 ) with minimized edge effect and the sound absorption performance on the specimen surface ( α ∞ ) were proposed as an evaluation indicator of agreement between the values. Experimental results show that diffusion inside the reverberation chamber is enhanced when α ∞ − α β E ≈ 0 < 0.02, for which sufficient diffusion can be assumed inside the reverberation chamber. In addition, to verify the validity of the proposed evaluation indicator, we investigated the relationship with the objective diffusion evaluation indicator for diffuse field configuration in the reverberation chamber, such as relative standard deviation of decay rate ( S r e l ) and Np values. The results of this study are expected to contribute to a more accurate estimation of the sufficient diffusion condition in the reverberation chamber, in evaluating the sound absorption performance of the material, and that inside the reverberation chamber.

scholarly journals Acoustic Panels Made of Paper Sludge and Clay Composites

2021 ◽  
Vol 13 (2) ◽  
pp. 637
Author(s):  
Tomas Astrauskas ◽  
Tomas Januševičius ◽  
Raimondas Grubliauskas
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Composite Panel ◽  
Sound Absorption Coefficient ◽  
Core Material ◽  
Paper Sludge ◽  
Frequency Range ◽  
Absorption Properties ◽  
Air Gaps ◽  
The Core

Studies on recycled materials emerged during recent years. This paper investigates samples’ sound absorption properties for panels fabricated of a mixture of paper sludge (PS) and clay mixture. PS was the core material. The sound absorption was measured. We also consider the influence of an air gap between panels and rigid backing. Different air gaps (50, 100, 150, 200 mm) simulate existing acoustic panel systems. Finally, the PS and clay composite panel sound absorption coefficients are compared to those for a typical commercial absorptive ceiling panel. The average sound absorption coefficient of PS-clay composite panels (αavg. in the frequency range from 250 to 1600 Hz) was up to 0.55. The resulting average sound absorption coefficient of panels made of recycled (but unfinished) materials is even somewhat higher than for the finished commercial (finished) acoustic panel (αavg. = 0.51).

scholarly journals Air permeability and sound absorption coefficient changes from ultrasonic treatment in a cross section of Malas (Homalium foetidum)

2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Chun-Won Kang ◽  
Eun-Suk Jang ◽  
Nam-Ho Lee ◽  
Sang-Sik Jang ◽  
Min Lee
Keyword(s):  
Absorption Coefficient ◽  
Ultrasonic Treatment ◽  
Sound Absorption ◽  
Gas Permeability ◽  
Treated Wood ◽  
Untreated Wood ◽  
Sound Absorption Coefficient ◽  
Permeability Constant ◽  
Average Value ◽  
Permeability Increase

AbstractWe investigated the effect of ultrasonic treatment on Malas (Homalium foetidum) gas permeability and sound absorption coefficient using the transfer function method. Results showed a longitudinal average Darcy permeability constant of 2.02 (standard deviation SD 0.72) for untreated wood and 6.15 (SD 3.07) for ultrasound-treated wood, a permeability increase of 3.04 times. We also determined the average sound absorption coefficients in the range of 50 to 6.4 kHz and NRC (noise reduction coefficient: average value of sound absorption coefficient value at 250, 500, 1000, and 2000 Hz) of untreated Malas. Those values were 0.23 (SD 0.02) and 0.13 (SD 0.01), respectively, while those of ultrasonic-treated Malas were 0.28 (SD 0.02) and 0.14 (SD 0.02), a 19.74% increase in average sound absorption coefficient.

Research of Possibilities of Using the Recycled Materials Based on Rubber and Textiles Combined with Vermiculite Material in the Area of ​​Noise Reduction

2014 ◽  
Vol 1001 ◽  
pp. 171-176 ◽  
Author(s):  
Pavol Liptai ◽  
Marek Moravec ◽  
Miroslav Badida
Keyword(s):  
Absorption Coefficient ◽  
Standing Wave ◽  
Sound Pressure Level ◽  
Sound Absorption ◽  
Sound Pressure ◽  
Sound Level ◽  
Pressure Level ◽  
Sound Absorption Coefficient ◽  
Physical Parameters ◽  
Materials Research

This paper describes possibilities in the use of recycled rubber granules and textile materials combined with vermiculite panel. The aim of the research is the application of materials that will be absorbing or reflecting sound energy. This objective is based on fundamental physical principles of materials research and acoustics. Method of measurement of sound absorption coefficient is based on the principle of standing wave in the impedance tube. With a sound level meter is measured maximum and minimum sound pressure level of standing wave. From the maximum and minimum sound pressure level of standing wave is calculated sound absorption coefficient αn, which can take values from 0 to 1. Determination of the sound absorption coefficient has been set in 1/3 octave band and in the frequency range from 50 Hz to 2000 Hz. In conclusion are proposed possibilities of application of these materials in terms of their mechanical and physical parameters.

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