Propagation characteristics of airborne ultrasonic waves in porous materials

The attenuation coefficient and propagation speed of an airborne ultrasound wave are measured for highly porous open-cell polyurethane foams and fibers at frequencies from 1 kHz to 1.7 MHz. A theoretical model is proposed to explain physically the frequency responses of the insertion loss and the sp...

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Bibliographic Details
Published inAcoustical Science and Technology Vol. 29; no. 1; pp. 82 - 85
Main Authors Aoki, Kenichi, Kamakura, Tomoo
Format Journal Article Conference Proceeding
LanguageEnglish
Published Tokyo ACOUSTICAL SOCIETY OF JAPAN 01.01.2008
Acoustical Society of Japan
Japan Science and Technology Agency
Subjects
Acoustics
Exact sciences and technology
Fundamental areas of phenomenology (including applications)
Physics
Porous materials
Slow wave
Structural acoustics and vibration
Tortuosity
Ultrasonic wave
Airborne sound
Hole
Open cell porosity
Glass
Cellular plastic
Porous material
Modeling
Frequency response
Ultrasound
Bulk density
Acoustic measurement
Air coupling
Ultrasonic wave
Tortuosity 43.55.Ev
Density distribution
Experimental study
Hydrodynamic drag
Wave transmission
Flow(fluid)
Polyurethane
Cement
Insertion loss
Porous materials. Slow wave
Plastics
Aeroacoustics
Bulk modulus
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Summary:The attenuation coefficient and propagation speed of an airborne ultrasound wave are measured for highly porous open-cell polyurethane foams and fibers at frequencies from 1 kHz to 1.7 MHz. A theoretical model is proposed to explain physically the frequency responses of the insertion loss and the speed of an air-coupled wave in porous materials. The model is derived from Biot’s flow resistance and density, Lambert’s bulk modulus for fluids in pores, and Zwikker and Kosten’s concept for the compliance of the side holes with entrance resistance. Using measured data of static flow resistance to determine the mean pore size and the proposed model, theoretical prediction is performed for the transmission losses and sound speeds. Good agreement between theory and experiment over the entire frequency range confirms the usefulness of the present model. In addition, the model provides findings for Nagy’s extra attenuation coefficient for a slow wave measured in cemented glass bead specimens and in sandstone for high-frequency ranges.
ISSN:1346-3969
1347-5177
DOI:10.1250/ast.29.82