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Deduction of tortuosity and porosity from acoustic reflection and transmission measurements on thick samples of rigid-porous materials

Umnova, O, Attenborough, K, Shin, HC and Cummings, A 2005, 'Deduction of tortuosity and porosity from acoustic reflection and transmission measurements on thick samples of rigid-porous materials' , Applied Acoustics, 66 (6) , pp. 607-624.

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Abstract

An acoustic method for obtaining the tortuosity, and porosity of thick samples of rigid porous materials consisting of large (>1 mm) grains or fibres is proposed. The method uses pulses with central frequencies close to 12 kHz and an approximate bandwidth of between 3 and 20 kHz. In this frequency range, inertial rather than viscous or scattering effects dominate sound propagation in large pores. This allows application of the high frequency limit of the “equivalent fluid” model. Both reflected and transmitted signals are used in the measurements. Tortuosity is deduced from the high frequency limit of the phase speed (obtained from transmission data) and porosity is obtained from the high frequency limit of the reflection coefficient once the tortuosity is known. The method is shown to give good results in the cases where significant scattering does not occur until frequencies much higher than the upper limit of the pulse bandwidth. Apart from its applicability to samples with several centimetres thickness, the method needs only one set of measurements with the sample to deduce both tortuosity and porosity. In principle the method can be used also to estimate characteristic lengths. However, the errors are found to be larger and the results less consistent than for tortuosity.

Item Type: Article
Themes: Subjects / Themes > Q Science > QC Physics > QC221-246 Acoustics - Sound
Subjects outside of the University Themes
Schools: Colleges and Schools > College of Science & Technology > School of the Built Environment
Colleges and Schools > College of Science & Technology > School of Computing, Science and Engineering > Acoustics Research Centre
Journal or Publication Title: Applied Acoustics
Publisher: Elsevier
Refereed: Yes
ISSN: 0003682X
Depositing User: H Kenna
Date Deposited: 03 Oct 2007 12:43
Last Modified: 20 Aug 2013 16:47
URI: http://usir.salford.ac.uk/id/eprint/463

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