Measurement of the bulk acoustic properties of fibrous materials at high temperatures |
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| Institution: | 1. School of Engineering and Design, Mechanical Engineering, Brunel University, Uxbridge, Middlesex UB8 3PH, UK;2. AAF Ltd., Bassington Lane, Cramlington, NE23 8AF Northumberland, UK;1. Faculty of Engineering and Environment, University of Southampton, Southampton SO16 7QF, UK;2. Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong Special Administrative Region;1. AAF Ltd., Bassington Lane, Cramlington, Northumberland NE23 8AF, UK;2. Centre for Audio, Acoustics and Vibration, University of Technology, Sydney, NSW 2007, Australia;3. KTH, The Marcus Wallenberg Laboratory (MWL), SE-100 44 Stockholm, Sweden;1. State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi''an Jiaotong University, Xi''an, 710049, PR China;2. State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, PR China;3. MIIT Key Laboratory of Multi-functional Lightweight Materials and Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, PR China;4. MOE Key Laboratory for Multifunctional Materials and Structures, Xi''an Jiaotong University, Xi''an, 710049, PR China;1. Université de Lyon, Ecole Nationale des Travaux Publics de l’Etat, LGCB - CELYA - CNRS 5513, 69518 Vaulx-en-Velin Cedex, France;2. Matelys 1 rue Baumer, 69120 Vaulx-en-Velin, France |
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| Abstract: | It is common for fibrous porous materials to be used in high temperature applications such as automotive and gas turbine exhaust silencers. Understanding the effect of temperature on the acoustic properties of these materials is crucial when attempting to predict silencer performance. This requires knowledge of the bulk acoustic properties of the porous materials and so this article aims to quantify the effect of temperature on the bulk acoustic properties of three fibrous materials: rock wool, basalt wool and an E-glass fibre. Measurements are undertaken here using a standard impedance tube that has been modified to accommodate temperatures of up to 500 °C. It is shown that measured data for the bulk acoustic properties may be collapsed using a standard Delany and Bazley curve fitting methodology provided one modifies the properties of the material flow resistivity and air to account for a change in temperature. Moreover, by using a previously proposed power law describing the dependence of the flow resistivity with temperature, one may successfully collapse data measured at every temperature and obtain the Delany and Bazley coefficients in the usual way. Accordingly, to predict the bulk acoustic properties of a fibrous material at elevated temperatures it is necessary only to measure these properties at room temperature, and then to apply the appropriate temperature corrections to the properties of the material flow resistivity and air when using the Delany and Bazley formulae. |
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| Keywords: | Porous materials High temperature Bulk acoustic properties |
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