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.

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.

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.

Broadening of the Sound Absorption Bandwidth of the Perforated Panel Using a Membrane-Type Resonator

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Xuezhi Zhu ◽  
Zhaobo Chen ◽  
Yinghou Jiao ◽  
Yanpeng Wang
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Degrees Of Freedom ◽  
Low Frequency ◽  
Absorption Capacity ◽  
Sound Absorption Coefficient ◽  
Sound Waves ◽  
Frequency Range ◽  
Absorption Bandwidth ◽  
Membrane Type

In order to broaden the sound absorption bandwidth of a perforated panel in the low frequency range, a lightweight membrane-type resonator is installed in the back cavity of the perforated panel to combine into a compound sound absorber (CSA). Because of the great flexibility, the membrane-type resonator can be vibrated easily by the incident sound waves passing through the holes of the perforated panel. In the low frequency range, the membrane-type resonator and the perforated panel constitute a two degrees-of-freedom (DOF)-resonant type sound absorption system, which generates two sound absorption peaks. By tuning the parameters of the membrane type resonator, a wide frequency band having a large sound absorption coefficient can be obtained. In this paper, the sound absorption coefficient of CSA is derived analytically by combining the vibration equation of the membrane-type resonator with the acoustic impedance equation of the perforated panel. The influences of the parameters of the membrane-type resonator on the sound absorption performance of the CSA are numerically analyzed. Finally, the wide band sound absorption capacity of the CSA is validated by the experimental test.

scholarly journals Mathematical model of acoustic characteristics of polyurethane foam used for sound absorption in aerospace engineering

2021 ◽  
Vol 20 (2) ◽  
pp. 53-62
Author(s):  
A. V. Kuznetsov ◽  
A. A. Igolkin ◽  
A. I. Safin ◽  
A. O. Pantyushin
Keyword(s):  
Mathematical Model ◽  
Finite Element ◽  
Absorption Coefficient ◽  
Finite Element Modeling ◽  
Sound Absorption ◽  
Sound Absorption Coefficient ◽  
Sound Insulation ◽  
Space Technology ◽  
Acoustic Characteristics ◽  
Element Modeling

When solving the problem of reducing the acoustic load on the spacecraft during the launch and flight of the launch vehicle, finite element modeling of acoustic processes under the nose fairing is carried out. To successfully solve this problem, a mathematical model of the acoustic characteristics of the material used for sound insulation is required. The existing mathematical models of the acoustic characteristics of materials are not suitable for the material under consideration that can be used in rocket and space technology to increase the sound insulation of the payload fairing + transfer compartment assembly. To obtain the sound absorption coefficient of the material, an impedance tube measurement method with two microphones is used. Using the method of differential evolution, the coefficients of a mathematical model of acoustic characteristics of the Delany-Bazley type for the specified material are selected. The sound absorption coefficient obtained experimentally and that calculated using the obtained model are compared; the average and maximum values of the error are shown. The resulting model will make it possible to carry out finite element modeling of acoustic and vibroacoustic processes under the nose fairing, taking into account the location of the sound-absorbing material.

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.

scholarly journals Influence of the geometry fidelity of resonant sound-absorbing liner samples on their acoustic characteristics

2019 ◽  
Vol 18 (1) ◽  
pp. 67-77
Author(s):  
O. Yu. Kustov ◽  
I. V. Khramtsov ◽  
R. V. Bulbovich
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Stokes Equations ◽  
Normal Wave ◽  
Helmholtz Resonator ◽  
Geometric Parameters ◽  
Sound Absorption Coefficient ◽  
Navier Stokes ◽  
Acoustic Characteristics ◽  
Design Values

Samples of sound-absorbing Helmholtz resonator-type liners of circular shape were manufactured from two types of ABS plastic and nylon on the basis of 3D modeling and 3D printing technology. Check samples were made of metal on a numerically controlled machine. Deviations of geometric parameters of the manufactured samples from the design values were determined by visual and dimensional inspection using high-precision equipment. The minimum deviations were obtained for check samples made of metal. The acoustic characteristics of the samples were experimentally determined using an interferometer with normal wave incidence at high sound pressure levels. Numerical simulation of the acoustic processes in the interferometer for the given samples was carried out on the basis of solving full Navier-Stokes equations with account for compressibility. The obtained values of the resonant frequency, impedance and sound absorption coefficient were compared with the experimental ones. It was noted that the impedance values are most sensitive to the deviations of the geometric parameters of the samples from the design values, while the deviations in the sound absorption coefficient and resonance frequency are not so sensitive to them.

scholarly journals Vibration damping and acoustic characteristics of sisal fibre–reinforced polypropylene composite

2018 ◽  
Vol 50 (1) ◽  
pp. 13-21 ◽  
Author(s):  
Yashwant S Munde ◽  
Ravindra B Ingle ◽  
I Siva
Keyword(s):  
Absorption Coefficient ◽  
Natural Frequency ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Experimental Results ◽  
Acoustic Properties ◽  
Sound Absorption Coefficient ◽  
Polypropylene Composite ◽  
Acoustic Characteristics ◽  
Sisal Fibre

Natural fibre composites attract industries because of their low density, low cost and the specific mechanical properties they possess in comparison to synthetic fibres. In this work, the randomly oriented sisal fibre–reinforced polypropylene composites are fabricated using extrusion–injection moulding technique. The aim of this study is to experimentally investigate the effect of fibre weight fraction (0%–30% in step of 10%) on vibrational damping and acoustic characteristics. The impulse hammer excitation technique is used to evaluate the free vibrational characteristics, namely, natural frequency and damping. An impedance tube is used in evaluating the acoustic properties, namely, sound absorption coefficient and transmission loss. Experimental results reveal that increase in fibre loading significantly alter the vibrational and acoustic response of the polypropylene composite. Modal analysis shows that incorporation of sisal fibres by 30 wt.% to polypropylene made the natural frequency superior when compared with other compositions. However, damping becomes worse with higher fibre content. In case of acoustic properties, incorporation of fibres at higher fraction enhances the sound absorption coefficient and transmission loss. Experimental results drive the research in development of such new materials system towards the application of vibration and sound diminutions.

scholarly journals Sound absorption characteristics of three species (binuang, balsa and paulownia) of low density hardwood

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Eun-Suk Jang ◽  
Chun-Won Kang
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Gas Permeability ◽  
Sound Absorption Coefficient ◽  
Low Density ◽  
High Porosity ◽  
Sound Waves ◽  
Low Frequencies ◽  
Absorption Performance ◽  
Closed Pore

Abstract In this study, the sound absorption coefficient of three low density hardwoods – binuang, balsa and paulownia – were investigated. Their gas permeability and pore size were measured, and their pore shapes were classified into through pore, blind pored, and closed pore, as specified by the International Union of Pure and Applied Chemistry (IUPAC). Among the three species, obvious that paulownia had lowest sound absorption when the two of others showed higher sound absorption. Although paulownia is a high porosity wood, most of its vessels are blocked by tyloses; it is therefore difficult for sound waves to enter its pores, which results in poor sound absorption performance. This study showed that the higher the through pore porosity, the higher was the gas permeability, which led to improvement of the sound absorption performance. It was also found that the sound absorption coefficient of the three species woods increased at low frequencies as the size of an air cavity between the specimens and tube’s wall increased.

Determination of the Effects of Air Gap and Hind Support on the Sound Absorption Coefficient of Biobased and Foam Materials

2012 ◽  
Author(s):  
N. V. David ◽  
M. N. Zainal ◽  
M. J. M. Nor
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Low Frequency ◽  
Air Gap ◽  
High Density ◽  
Sound Absorption Coefficient ◽  
Sound Waves ◽  
Fibrous Media ◽  
Rigid Foam ◽  
Quarter Wavelength

The sound absorption characteristics of wooden and porous materials including fibrous media and porous foams vary with the nature of their surface porosity. The low frequency absorption, which is of interest in noise control engineering, of these material types is generally enhanced by introducing an air gap of a certain width or a flexible support at the rear face of the material posterior to the impinging sound waves. This study investigates the effect of air gap with and without hind support on the low frequency absorption of a kenaf/epoxy composite, a Meranti wood, a low-density rigid foam and a high-density rigid foam. The sound absorption coefficient of these materials are determined using the two-microphone impedance tube transfer-function method according to ISO 10534-2 standard in the frequency range between 20 Hz and 1600 Hz. In this study, 5-mm, 10-mm, 50-mm and 100-mm wide air gaps are introduced at the posterior of the specimens to measure the influence of the quarter-wavelength absorption on sound absorption coefficient. Backing panels made from polyethylene are used to study the effect of hind support on sound absorption coefficient at different frequencies. The dBFA Suite 4.8.1 program is used to acquire and process the acoustic signals and the SCS8100 software package is employed for the computation of sound absorption coefficient. The sound absorption coefficient and characteristics of each material within the range of frequency tested are discussed based on the width of air gap (i.e., the quarter-wavelength effect) in tandem with the presence or absence of the hind support. It is found that the low frequency absorption of the high-density foam with the hind support improved the absorption by 50% as the air gap is increased from 0 to 100 mm. The opposite effect is observed for the other materials tested whereby the sound absorption coefficient is reduced by 30 to 40% with the hind support.

scholarly journals SOUND ABSORPTION OF SOUND SUPRESSING LIGHTWEIGHT STRUCTURED PANELS

Akustika ◽  
2019 ◽  
Vol 34 ◽  
pp. 40-43
Author(s):  
Valery Murzinov ◽  
Pavel Murzinov ◽  
Sergey Popov ◽  
Julia Taratinova
Keyword(s):  
Absorption Coefficient ◽  
Surface Density ◽  
Sound Absorption ◽  
Sound Absorption Coefficient ◽  
Sound Insulation ◽  
Acoustic Characteristics ◽  
Absorbing Materials

Description of the effective soundproofing panel is presented. For this panel, the ratio of acoustic characteristics and surface density exceeds many modern sound insulation and sound absorbing materials and structures. This article is devoted to modeling the sound absorption coefficient of the soundproof panel. The article presents formulas for determining the coefficient of sound absorption. Construction of a sound suppressed lightweight structured panel (SSLSP) developed by the authors is shown. Comparison of the effectiveness of the SSLSP panel and modern sound-proof materials is shown.

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