The Acoustic Properties of Expanded Clay Granulates

2002 ◽  
Vol 9 (2) ◽  
pp. 85-98 ◽  
Author(s):  
F. Asdrubali ◽  
K. V. Horoshenkov
Keyword(s):  
Experimental Data ◽  
Absorption Coefficient ◽  
Acoustic Impedance ◽  
Acoustic Properties ◽  
Low Density ◽  
Frequency Range ◽  
Approximation Approach ◽  
Acoustic Performance ◽  
Granular Base ◽  
Good Agreement

The purpose of this work is to characterise experimentally and theoretically the acoustic performance of mixes of loose expanded clay granulates. The surface acoustic impedance is obtained from measurements in the impedance tube and predicted using the Pade approximation approach. The random incidence absorption coefficient is measured using the ISO 345/85 method. Experimental data for the surface acoustic impedance are used to deduce the porosity, tortuosity and the statistical pore size distribution; these parameters are difficult to obtain directly, because of the relatively low density of the loose granulates and the fact that the granular base contains 5–30% of the closed, unconnected pores. Good agreement between the theory and the results is found; 50–100 mm layers of expanded clay granulates can be used efficiently for noise control over a broad frequency range.

The Behaviour of Railway Wheelsets and Track at High Frequencies of Excitation

1982 ◽  
Vol 24 (2) ◽  
pp. 103-111 ◽  
Author(s):  
S. L. Grassie ◽  
R. W. Gregory ◽  
K. L. Johnson
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Contact Force ◽  
Analytical Methods ◽  
Dynamical Response ◽  
Frequency Range ◽  
High Frequencies ◽  
Good Agreement

The dynamical response in the frequency range 50–1500 Hz is investigated of a railway wheelset resting on the track and excited vertically, laterally and longitudinally at a point of contact. A mathematical model of a railway wheelset is developed which comprises a few simple components to which analytical methods can be applied. Good agreement is obtained between experimental data and calculations made using this model. For a given sinusoidal displacement imposed between wheel and rail, the contact force is in general greatest longitudinally and least laterally.

THEORY OF THE PRESSURE-INDUCED ROTATIONAL SPECTRUM OF HYDROGEN

1959 ◽  
Vol 37 (10) ◽  
pp. 1187-1198 ◽  
Author(s):  
J. Van Kranendonk ◽  
Z. J. Kiss
Keyword(s):  
Experimental Data ◽  
Distribution Function ◽  
Absorption Coefficient ◽  
Pair Distribution Function ◽  
Wave Functions ◽  
Rotational Line ◽  
Induction Effect ◽  
Rotational Spectrum ◽  
Absorption Coefficients ◽  
Good Agreement

The theory of induced infrared absorption developed previously is applied to the pressure-induced rotational spectrum of hydrogen. The intensity of the rotational band is due mainly to the quadrupolar induction effect, and to a small interference effect between the quadrupolar and overlap moments. From the experimental data on the binary absorption coefficients, values of the angle-dependent overlap moments are obtained for H2–He, H2–H2, H2–Ne, H2–N2, and H2–A. A calculation of the overlap moment for pure H2 is presented. Rosen-type wave functions appear to be inadequate for a calculation of the small angle-dependent rotational as well as vibrational overlap moments. The temperature dependence of the binary absorption coefficient is calculated, taking into account the quantum effects in the pair distribution function, and found to be in good agreement with the experimental data. The dependence on the ortho–para ratio is also discussed. The double rotational line S(1) + S(1) has been observed and its intensity measured.

Collision–induced absorption in gaseous methane at low temperatures

1986 ◽  
Vol 64 (7) ◽  
pp. 763-767 ◽  
Author(s):  
I. R. Dagg ◽  
A. Anderson ◽  
S. Yan ◽  
W. Smith ◽  
C. G. Joslin ◽  
...  
Keyword(s):  
Experimental Data ◽  
Low Temperatures ◽  
Low Frequency ◽  
Frequency Region ◽  
Experimental Results ◽  
Published Data ◽  
Frequency Range ◽  
Simple Method ◽  
Induced Absorption ◽  
Good Agreement

A recently developed theory for collision-induced absorption in methane is compared with experimental results over a wider spectral range and at lower temperatures than previously reported. The present experimental results covering the frequency range below 400 cm−1 exhibit good agreement with other recently published data. The theory shows excellent agreement with experiment in the low-frequency region below approximately 200 cm−1 but underestimates the experimental data somewhat at higher frequencies. Possible theoretical reasons for this discrepancy are given. The theory represents a simple method of obtaining a good estimate of the collision-induced absorption spectra of methane in this frequency region and for extrapolating to lower temperatures for which experimentation is not feasible. In addition, the moments α1 and γ1are compared with earlier determinations and indicate good agreement with the previously obtained values for the octupole and hexadecapole moments of methane.

Experimental Study of Acoustic Performance of Porous Metals at High Temperatures

2018 ◽  
Vol 933 ◽  
pp. 373-379
Author(s):  
Jun Zhe Zhang ◽  
Xiao Peng Wang ◽  
Bo Zhang ◽  
Li Hong Zhang
Keyword(s):  
High Temperatures ◽  
Temperature Stability ◽  
Porous Metal ◽  
Acoustic Properties ◽  
Temperature Fields ◽  
Testing System ◽  
Porous Metals ◽  
Ambient Temperatures ◽  
Acoustic Performance ◽  
Good Agreement

Based on an improved two-microphone transfer function method, a testing system for the exploration of acoustic performance of porous materials under high temperature conditions was developed with porous foam copper as one of research objects. The acoustic performances of some porous metallic materials were studied in the temperature range of 300°C to 700°C under the premise of ensuring the temperature stability that makes the measurement uncertainty be ± 6°C at high temperatures. The sound absorption coefficient and the acoustic impedance ratio of porous coppers at different ambient temperatures were acquired accordingly. And then the influence of the variation of temperature fields on the acoustic properties of porous metals was analyzed. The experimental results are in good agreement with the theoretical analysis, which proves the rationality of design of the device and provides important references and specific guidance for future study of the acoustic properties of porous metal materials.

Sound absorption characterization of aluminum foam made by press infiltration casting

2016 ◽  
Vol 12 (4) ◽  
pp. 737-747 ◽  
Author(s):  
J.X. Sun ◽  
C.Y. Duan ◽  
P.S. Liu
Keyword(s):  
Experimental Data ◽  
Absorption Coefficient ◽  
Sound Wave ◽  
Sound Absorption ◽  
Aluminum Foam ◽  
Peak Frequency ◽  
Experimental Result ◽  
Content Type ◽  
Improved Model ◽  
Good Agreement

Purpose The purpose of this paper is to investigate the sound absorption by modeling for the aluminum foam produced by press infiltration casting. Design/methodology/approach First use Johnson-Allard-Champoux (JAC) model to calculate the sound absorption coefficient of the present aluminum foam, and then improve it after finding its deviation from the experimental data, so as to get an improved model that could have a good agreement with the experimental result. Findings Using JAC model to calculate the sound absorption coefficient of the present aluminum foam, it is found that the model may have a good agreement with the experimental data only for the sound wave frequency below the absorption peak frequency, but a large deviation from the experimental result for the sound wave frequency above this frequency. Originality/value Improving JAC model by means of two factors, i.e., the absorption peak frequency and the specific surface area, the resultant improved model could be in good agreement with the experimental data.

scholarly journals An experimental study on the effects of compression on the acoustic performance of porous fibrous materials

2021 ◽  
Author(s):  
Ching Chi Suen
Keyword(s):  
Absorption Coefficient ◽  
Mineral Wool ◽  
Fibrous Materials ◽  
Frequency Range ◽  
Compression Technique ◽  
Acoustic Performance ◽  
Initial Errors ◽  
Experimental Errors ◽  
Flow Resistivity ◽  
Porous Fibrous Material

The current investigation experimentally studied the effects of compression on the acoustic performance of porous fibrous material. Two inch and four inch thick samples of fiberglass and three varying densities of mineral wool were tested using two different impedance tube sizes at compression rates of 1, 1.3 and 2. The absorption coefficient was measured using Chung and Blaser’s method. The flow resistivity was measured using Tao et al.’s method. Overall, the 4” samples resulted in steadier results than the 2” samples. Compression generally led to a decrease in absorption coefficient and an increase in flow resistivity. These effects were most evident in the lower frequency range. Although there were some experimental errors in sample preparation, sample variation, compression technique, testing order and other initial errors, the current study demonstrated that the effects of compression on insulation should be not be overlooked.

Acoustic performance analysis of Helmholtz resonators with conical necks and its application

2019 ◽  
Vol 67 (3) ◽  
pp. 155-167 ◽  
Author(s):  
Haitao Liu
Keyword(s):  
Finite Element ◽  
Prediction Model ◽  
Transmission Loss ◽  
Low Frequency ◽  
Wide Band ◽  
Acoustic Properties ◽  
Frequency Range ◽  
Acoustic Attenuation ◽  
Acoustic Performance ◽  
Helmholtz Resonators

The acoustic properties of the Helmholtz resonators with conical necks, which have broad acoustic attenuation band performance in the low frequency range, are investigated in this study. In order to investigate its wide-band acoustic attenuation mechanism, three-dimensional finite element models for the Helmholtz resonators with different necks are built respectively. The acoustic performance prediction model based on the one-dimensional analytical approach with acoustic length corrections is built to calculate the transmission loss results more efficiently, and the formula for calculating the resonance frequency is also derived. Then, the prediction model and the formula are verified by finite element method and experiment, which show good agreements. As a result, the prediction model is applied to analyze the sound attenuation properties of the Helmholtz resonators with conical necks, and the results show that the acoustic attenuation bandwidth in the low frequency range is improved by increasing the taper angle of the neck. At last, the approaches for the Helmholtz resonators with conical necks are applied to design an actual middle silencer of a passenger car. The results show that the designed middle silencer performs much better than the original one, which can effectively eliminate the exhaust order noise to meet the standard of exhaust noise control. The test results fully reveal that the Helmholtz resonators with conical necks in the muffler can play a better role in eliminating exhaust order noise, and the approaches proposed in this article can effectively guide the design of Helmholtz resonators with conical necks.

EXPERIMENTAL DETERMINATION OF ACOUSTIC BEHAVIOR OF BUILDING MATERIALS BY MEANS OF ACCELEROMETERIC MEASUREMENTS

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Lukáš Fiala ◽  
Petr Konrád ◽  
Robert Černý
Keyword(s):  
Experimental Determination ◽  
Urban Areas ◽  
Building Materials ◽  
Acoustic Properties ◽  
Traffic Load ◽  
Acoustic Behavior ◽  
Frequency Range ◽  
Acoustic Performance ◽  
Acoustic Load

In Central Europe, brick blocks with incorporated system of voids ensuring good thermal properties are widely used in the building industry. In the present, increasingly higher acoustic load gains on importance especially in the surroundings of places with high traffic load, places close to the airports or in urban areas. This fact should be taken into consideration in the design of constructions in order to ensure their good acoustic performance. The very first step of such design lies in the experimental determination of acoustic properties of the reference construction elements which are, if necessary, subsequently optimized by adjustment of the voids volume and geometry or filling of the voids by various bulk fillers ensuring a higher level of scattering of the propagating acoustic signal. In this paper, steel prism and brick block were subjected to measurements by accelerometers in the frequency range 1 – 10 kHz in order to compare acoustic behavior of materials with a significantly different structure. Finally, frequency-dependent displacements in accelerometers position,

scholarly journals Acoustic Properties of Sound Absorber from Modified Polyester with Filler Sodium Bicarbonate

2018 ◽  
Vol 34 (4) ◽  
pp. 2187-2191
Author(s):  
Nasmi Herlina Sari ◽  
Jauhar Fajrin
Keyword(s):  
Absorption Coefficient ◽  
Sodium Bicarbonate ◽  
Acoustic Impedance ◽  
Sound Absorption ◽  
Polyester Resin ◽  
Acoustic Properties ◽  
Acoustic Parameters ◽  
Absorbent Material ◽  
Sound Absorber ◽  
Absorption Performance

The combination of low price, ease of manufacturing and waterproofing characteristics has placed polyester resin as a potential sound absorbent material. Previous studies showed that adding filler material to the blending may increase the acoustics properties of a sound absorbent material. This study aims to investigate the potential of sodium bicarbonate (NaHCO3) to be employed as a filler to improve the acoustic properties of the sound absorber made of polyester resin. Two important acoustic parameters were carefully assessed; absorption coefficient and acoustic impedance. The results showed that the sound absorption performance increased significantly at low and medium frequencies in the presence of NaHCO3 filler in polyester resin. Meanwhile, the use of a back cavity on the absorbent material reduced the sound absorption performance of materials at low and medium frequencies. This suggests that sound absorber made of polyester with sodium bicarbonate filler may be used as an alternative for sound absorber materials.

scholarly journals Оптические свойства спироида C-=SUB=-300-=/SUB=-

2019 ◽  
Vol 89 (2) ◽  
pp. 169
Author(s):  
С.Г. Ястребов ◽  
М.С. Чекулаев ◽  
A. Siklitskaya
Keyword(s):  
Experimental Data ◽  
Matrix Element ◽  
Optical Absorption ◽  
Absorption Coefficient ◽  
Exchange Interaction ◽  
Optical Absorption Coefficient ◽  
Local Curvature ◽  
The Matrix ◽  
Strong Coupling Method ◽  
Good Agreement

AbstractCalculation results of the electronic spectrum of carbon nanospiroid C_300 are presented. The π-electron structure of the spiroid is calculated using the strong coupling method, in which the matrix element of the exchange interaction of neighboring electrons (the resonance integral) is considered as being dependent on the local curvature of the spiroid surface. The optical absorption coefficient is calculated in the framework of the Tautz model and the result is compared with experimental and astrophysical observational data. The calculated and experimental data are in good agreement.

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