Advances in aircraft and spacecraft science

Techno-Press (테크노프레스)
권호 표지
DOI QR코드

DOI QR Code

Effects of macroporosity and double porosity on noise control of acoustic cavity

  • Sujatha, C. (Machine Design Section, Department of Mechanical Engineering, Indian Institute of Technology Madras) ;
  • Kore, Shantanu S. (Machine Design Section, Department of Mechanical Engineering, Indian Institute of Technology Madras)
  • Received : 2015.06.03
  • Accepted : 2015.09.21
  • Published : 2016.07.25
⟨ Previous Next ⟩

Abstract

Macroperforations improve the sound absorption performance of porous materials in acoustic cavities and in waveguides. In an acoustic cavity, enhanced noise reduction is achieved using porous materials having macroperforations. Double porosity materials are obtained by filling these macroperforations with different poroelastic materials having distinct physical properties. The locations of macroperforations in porous layers can be chosen based on cavity mode shapes. In this paper, the effect of variation of macroporosity and double porosity in porous materials on noise reduction in an acoustic cavity is presented. This analysis is done keeping each perforation size constant. Macroporosity of a porous material is the fraction of area covered by macro holes over the entire porous layer. The number of macroperforations decides macroporosity value. The system under investigation is an acoustic cavity having a layer of poroelastic material rigidly attached on one side and excited by an internal point source. The overall sound pressure level (SPL) inside the cavity coupled with porous layer is calculated using mixed displacement-pressure finite element formulation based on Biot-Allard theory. A 32 node, cubic polynomial brick element is used for discretization of both the cavity and the porous layer. The overall SPL in the cavity lined with porous layer is calculated for various macroporosities ranging from 0.05 to 0.4. The results show that variation in macroporosity of the porous layer affects the overall SPL inside the cavity. This variation in macroporosity is based on the cavity mode shapes. The optimum range of macroporosities in poroelastic layer is determined from this analysis. Next, SPL is calculated considering periodic and nodal line based optimum macroporosity. The corresponding results show that locations of macroperforations based on mode shapes of the acoustic cavity yield better noise reduction compared to those based on nodal lines or periodic macroperforations in poroelastic material layer. Finally, the effectiveness of double porosity materials in terms of overall sound pressure level, compared to equivolume double layer poroelastic materials is investigated; for this the double porosity material is obtained by filling the macroperforations based on mode shapes of the acoustic cavity.

Keywords

References

  1. Allard, J.F. and Atalla, N. (2009), Propagation of Sound in Porous Media: Modelling Sound Absorbing Materials, Wiley, United Kingdom.
  2. Atalla, N., Panneton, R. and Debergue, P., (1998), "A mixed displacement pressure formulation for poroelastic materials", Acoust. Soc. Am., 98(104), 1444-1452.
  3. Atalla, N., Sgard, F., Only, X. and Panneton, R. (2001 ), "Acoustic absorption of macro perforated porous materials", J. Sound Vib., 243(4), 659-678. https://doi.org/10.1006/jsvi.2000.3435
  4. Besset, S. and Ichchou, M.I. (2011), "Acoustic absorption material optimization in the mid-high frequency range", Appl. Acoust., 72(9), 632-638. https://doi.org/10.1016/j.apacoust.2011.01.014
  5. Goransson, P. (1995), "A weighted residual formulation of the acoustic wave propagation through a flexible porous material and comparison with limp material model", J. Sound Vib., 182, 479-494. https://doi.org/10.1006/jsvi.1995.0211
  6. Ih, J.Y., Heo, Y., Cho, S. and Cho W. (2011), "Optimal positioning of sources and absorbing materials for the sound field rendering by array speakers", Forum Acusticum, 6th Conference, Denmark, June-July.
  7. Lenin, M.C. and Padmanabhan, C. (2010), "Noise control of rectangular cavity using macro perforated poroelastic materials", Appl. Acoust., 71, 418-430. https://doi.org/10.1016/j.apacoust.2009.11.012
  8. Panneton, R. and Atalla, N. (1997), "An efficient finite element scheme for solving the three dimensional poroelasticity problem in acoustics", J. Acoust. Soc. Am., 101(6), 3287-3298. https://doi.org/10.1121/1.418345
  9. Petyt, M., Lea, J. and Koopmann, G.H. (1976), "A finite ele1nent method determining the acoustic models of irregular shaped cavities", J. Sound Vib., 45(4), 495-502. https://doi.org/10.1016/0022-460X(76)90730-6
  10. Sgard, F.C., Only, X., Atalla, N. and Castel, F. (2005), "On the use of perforations to improve the sound absorption of porous materials", Appl. Acoust., 66,625-651. https://doi.org/10.1016/j.apacoust.2004.09.008
  11. Totaro, N. and Guyader, J. (2011), "Efficient positioning of absorbing material in complex systems by using the Patch Transfer Function method", J. Sound Vib., 331(2012), 3130-3143.
  12. Zienkiewicz, O.C. and Taylor, R. (1989), The Finite Element Method, Mcgraw-Hill, London