Sound absorbers including porous materials are used widely for noise control. The most widely-exploited and acknowledged absorption mechanism in porous materials is viscous friction due to relative motion between solid and fluid. Acoustical performance of woven (carpet) and nonwoven (felt) materials made of wool using a traditional technique was investigated. Absorption coefficient of felt was measured using standing wave tube method with and without an air cavity. Data were compared with predictions determined using the laws of Delany and Bazely. Very good agreement between data and predictions was observed. Sound absorption coefficients of both materials also were measured using an impedance gun technique over a wider frequency range. Absorption coefficient obtained using impedance gun method shows that the absorption coefficient of felt is higher than the absorption coefficient of carpet for mid and higher frequencies. Furthermore insertion loss (IL) of the felt was measured in a circular duct. It is found that felt can attenuate sound pressure level between 1 dB and 10 dB.
References
[1]
Sardar, J. (2008) A Brief Review on Sound Absorption Characteristics of Non-Woven Structures. Indian Institute of Technology Delhi Press.
[2]
Barber, E.J.W. (1991) Prehistoric Textiles: The Development of Cloth in the Neolithic and Bronze Ages, with Special Reference to the Aegean. Princeton University Press, Princeton.
[3]
Bender, L. (1992) North European Textiles until AD 1000. Aarchus University Press, Aarchus.
[4]
Zwikker, C. and Kosten, C.W. (1949) Sound Absorbing Materials. Elsevier, New York.
[5]
Biot, M.A. (1956) Theory of Propagation of Elastic Wave in a Fluid-Saturated Porous Solid. I. Low-Frequency Range. Journal of the Acoustical Society of America, 28, 168-178. https://doi.org/10.1121/1.1908239
[6]
Biot, M.A. (1962) Mechanics of Deformation and Acoustic Propagation in Porous Media. Journal of Applied Physics, 33, 1482-1498.
https://doi.org/10.1063/1.1728759
[7]
Delany, M.E. and Bazley, E.N. (1970) Acoustical Properties of Fibrous Absorbent Materials. Applied Acoustics, 3, 105-116.
https://doi.org/10.1016/0003-682X(70)90031-9
[8]
Attenborough, K. (1982) Acoustical Characteristics of Porous Materials. Physics Reports, 82, 179-227. https://doi.org/10.1016/0370-1573(82)90131-4
[9]
Swift, M.J., Horoshenkov, K.V., Leclaire, P. and Hothersall, D.C. (2000) On the Effect of the Bending Vibration on the Acoustic Properties of Thin Poroelastic Plates. Journal of the Acoustical Society of America, 107, 1786-1789.
https://doi.org/10.1121/1.428577
[10]
Aygün, H. and Attenborough, K. (2008) Sound Absorption by Clamped Poroelastic Plates. Journal of the Acoustical Society of America, 124, 1550-1556.
https://doi.org/10.1121/1.2951586
[11]
Huang, L. (1999) A Theoretical Study of Duct Noise Control by Flexible Panels. Journal of the Acoustical Society of America, 106, 1801-1809.
https://doi.org/10.1121/1.427930
[12]
Huang, L. (2000) Experimental Study of Sound Propagation in a Flexible Duct. Journal of the Acoustical Society of America, 108, 624-631.
https://doi.org/10.1121/1.429594
[13]
Ramamoorthy, S., Grosh, K. and Nawar, T.G. (2003) Structural Acoustic Silencers—Design and Experiment. Journal of the Acoustical Society of America, 114, 2812-2824. https://doi.org/10.1121/1.1616926
[14]
Munjal, M.L. (1987) Acoustics of Ducts and Mufflers. Wiley, New York.
[15]
Tang, W.C. and Lin, W.Z. (2003) Stiff Light Composite Panels for Duct Noise Reduction. Applied Acoustics, 64, 511-524.
https://doi.org/10.1016/S0003-682X(02)00109-3
[16]
Astley, R.J., Cummings, A. and Sormaz, N. (1991) A Finite Element Scheme for Acoustic Propagation in Flexible-Walled Ducts with Bulk-Reacting Liners, and Comparison with Experiment. Journal of Sound and Vibration, 150, 119-138.
https://doi.org/10.1016/0022-460X(91)90406-A
[17]
Cummings, A. and Chang, I.J. (1988) Sound Attenuation of a Finite Length Dissipative Flow Duct Silencer with Internal Mean Flow in the Absorbent. Journal of Sound and Vibration, 127, 1-17. https://doi.org/10.1016/0022-460X(88)90347-1
[18]
Aygün, H. and Attenborough, K. (2008) The Insertion Loss of Perforated Porous Plates in a Duct without and with Mean Air Flow. Applied Acoustics, 69, 506-513.
https://doi.org/10.1016/j.apacoust.2006.12.007
[19]
Aygün, H. (2006) The Design of Noise Attenuating Devices Incorporating Elastic Porous Structures. Ph.D. Thesis, University of Hull, Kingston upon Hull.
[20]
BS EN ISO 10534-1 (2001) Acoustics. Determination of Sound Absorption Coefficient and Impedance in Impedances Tubes. Method Using Standing Wave Ratio.
[21]
Microflown Tech. http://www.microflown.com
[22]
International Standard ISO 7235 (1991) Acoustics-Measurement Procedures for Ducted Silencers—Insertion Loss, Flow Noise and Total Pressure Loss.
[23]
Beranek, L.L. and Ver, I.L. (1992) Noise and Vibration Control Engineering: Principles and Applications. Wiley Inter-Science, Hoboken.
[24]
Allard, J.F. and Atalla, N. (2009) Propagation of Sound in Porous Media: Modelling Sound Absorbing Materials. 2nd Edition, Wiley-Blackwell, Hoboken.
