scholarly journals Long-tube method for field determination of sound-absorption coefficients

1952 ◽  
Vol 49 (1) ◽  
pp. 17 ◽  
Author(s):  
E. Jones ◽  
S. Edelman ◽  
A. London
Keyword(s):  
Sound Absorption ◽  
Absorption Coefficients

Experimental study of wood acoustic absorption characteristics

Holzforschung ◽  
2014 ◽  
Vol 68 (4) ◽  
pp. 467-476 ◽  
Author(s):  
Jerzy Smardzewski ◽  
Wojciech Batko ◽  
Tadeusz Kamisiński ◽  
Artur Flach ◽  
Artur Pilch ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Acoustic Properties ◽  
Acoustic Absorption ◽  
Laboratory Measurements ◽  
Absorption Coefficients ◽  
Tropical Zone ◽  
Fiber Dimensions ◽  
Air Flow Resistivity ◽  
Oak Ash

Abstract The objective of this study was to determine normal impedance on the surface as well as sound absorption coefficients for several wood species from Europe and from the tropical zone. The mathematical models of Miki, Attenborough, and Allard – dealing with acoustic properties of porous materials – have also been compared. The air flow resistivity exhibits a distinct link between fiber dimensions and wood porosity. The highest sound absorption coefficient was found for oak, ash, sapeli, and pine woods at 2 kHz frequency. The Attenborough model provides results closest to laboratory measurements, although it still requires significant improvements. The Miki and Allard models have some drawbacks and should be applied with reservation for the determination of wood acoustic properties.

scholarly journals Diffuse Sound Absorptive Properties of Parallel-Arranged Perforated Plates with Extended Tubes and Porous Materials

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1091 ◽  
Author(s):  
Dengke Li ◽  
Daoqing Chang ◽  
Bilong Liu
Keyword(s):  
Boundary Condition ◽  
Porous Material ◽  
Porous Materials ◽  
Sound Absorption ◽  
Azimuthal Angle ◽  
Octave Band ◽  
Frequency Range ◽  
Absorption Coefficients ◽  
Perforated Plates ◽  
Absorption Performance

The diffuse sound absorption was investigated theoretically and experimentally for a periodically arranged sound absorber composed of perforated plates with extended tubes (PPETs) and porous materials. The calculation formulae related to the boundary condition are derived for the periodic absorbers, and then the equations are solved numerically. The influences of the incidence and azimuthal angle, and the period of absorber arrangement are investigated on the sound absorption. The sound-absorption coefficients are tested in a standard reverberation room for a periodic absorber composed of units of three parallel-arranged PPETs and porous material. The measured 1/3-octave band sound-absorption coefficients agree well with the theoretical prediction. Both theoretical and measured results suggest that the periodic PPET absorbers have good sound-absorption performance in the low- to mid-frequency range in diffuse field.

Method of Testing of Sound Absorption Properties of Materials Intended for Ultrasonic Noise Protection

2013 ◽  
Vol 38 (2) ◽  
pp. 191-195 ◽  
Author(s):  
Dariusz Pleban
Keyword(s):  
Sound Absorption ◽  
Free Field ◽  
Tone Burst ◽  
Mineral Wool ◽  
Frequency Range ◽  
Absorption Properties ◽  
Open Cell Foam ◽  
Properties Of Materials ◽  
Cell Foam

Abstract Efficient ultrasonic noise reduction by using enclosures requires the knowledge of absorbing properties of materials in the frequency range above 4 kHz. However, standardized methods enable determination of absorption coefficients of materials in the frequency range up to 4 kHz. For this reason, it is proposed to carry out measurements of the sound absorption properties of materials in the free field by means of a tone-burst technique in the frequency range from 4 kHz to 40 kHz at angles of incidence varying from 0° to 60°. The absorption coefficient of a material is calculated from the reflection coefficient obtained by reflecting a tone-burst from both a perfectly reflecting panel and a combination of this panel and the sample of the tested material. The tests results show that mineral wool and polyurethane open-cell foam possess very good absorbing properties in this frequency range.

The Use of Reverse Mirage Spectroscopy to Determine the Absorption Coefficient of Liquid Methanol at CO2 Laser Wavelengths

1989 ◽  
Vol 43 (1) ◽  
pp. 148-153 ◽  
Author(s):  
Dane Bićanić ◽  
Siegfried Krüger ◽  
Paul Torfs ◽  
Bruno Bein ◽  
Frans Harren
Keyword(s):  
Absorption Coefficient ◽  
Co2 Laser ◽  
Probe Beam ◽  
Laser Emission ◽  
Wavelength Region ◽  
Experimental Setup ◽  
Absorption Coefficients ◽  
Experimental Conditions ◽  
Liquid Samples

An experimental setup for performance of reverse mirage spectroscopy at CO2 laser wavelengths on liquid samples having high values of absorption coefficients is described. One and the same liquid is used as both the absorbing and deflecting medium. The Rosencwaig-Gersho theory has been applied, and the choice of experimental conditions that would enable determination of absorption coefficient β from the magnitude of photothermal signals measured at two different probe beam distances (probing locations) is discussed. The usefulness of this technique (essentially not inhibited by the requirements imposed on the sample's thickness) is tested on methanol having absorption coefficients β close to 300 cm−1 in the wavelength region covered by CO2 laser emission.

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