The present paper focuses on the effect of air jets through a perforated thin plate on the characteristics of an acoustic absorption coefficient. We measured the flow rate, internal pressure, acoustic pressure, and transfer function by using an improved acoustic impedance tube. The normal incidence absorption coefficient was calculated from the measured transfer function using transfer function methods. As a result, the frequency characteristics of the acoustic absorption coefficient against the frequency showed a maximum value at the local frequency. The peak frequency of the acoustic absorption coefficient depended on the thickness of the background air space and the thickness of the perforated plate. As the flow rate increased through the micropores, the peak level of the acoustic absorption coefficient also increased until a flow rate of 80 l /min. As the flow rate further increased, the peak level of the acoustic absorption coefficient decreased and that of the high frequency band increased.
Cite this paper
|||Howe, M.S. (1979) On the Theory of Unsteady High Reynolds Number Flow through a Circular Aperture. Proceedings of the Royal Society London, Series A, 366, 205-223.
|||Hughes, I.J. and Dowling, A.P. (1990) The Absorption of Sound by Perforated Linings. Journal of Fluid Mechanics, 218, 299-335.
|||Dowling, A.P. and Hughes, I.J. (1992) Sound Absorption by a Screen with a Regular Array of Slits. Journal of Sound Vibration, 156, 387-405.
|||Jing, X. and Sun, X. (1999) Experimental Investigation of Perforated Liners with Bias Flow. The Journal of the Acoustical Society of America, 106, 2436-2441.
|||Jing, X. and Sun, X. (2000) Effect of Plate Thickness on Impedance of Perforated Plates with Bias Flow. AIAA Journal, 38, 1573-1578.
|||Dupere, I.D.J. and Dowling, A.P. (2002) The Absorption of Sound by Helmholtz Resonators with and without Flow. American Institute of Aeronautics and Astronautics, 2002-2590.
|||Luong, T., Howe, M.S. and McGowan, R.S. (2005) On the Rayleigh Conductivity of a Bias-flow Aperture. Journal of Fluids and Structure, 21, 769-778.
|||Wada, K., Ishii, T. and Morimoto, J. (2012) Acoustic Absorption Characteristics of Sound Waves Interacting with Fine-Scale Jets. 2012 Symposium on Environmental Engineering, No. 12-6, No. 122.|
|||Scarpato, A., Tran, N., Ducruix, S. and Schuller, T. (2012) Modeling the Damping Properties of Perforated Screens Traversed by a Bias Flow and Backed by a Cavity at Low Strouhal Number. Journal of Sound and Vibration, 331, 276-290.
|||Wada, K. and Ishii, T. (2013) Acoustic Absorption of Perforated Plates with Fine Jets: Experimental Results and Analytical Models. Proceedings of 4th International Conference on Jets, Wakes and Separated Flows, Nagoya, 17-21 September 2013, Paper No. ICJWSF2013-1127.|
|||Scarpato, A., Ducruix, S. and Schuller, T. (2013) Optimal and Off-Design Operations of Acoustic Dampers Using Perforated Plates Backed by a Cavity. Journal of Sound and Vibration, 332, 4856-4875.
|||White, F.M. (1994) Fluid Mechanics. Third Edition, McGraw Hill, Boston.|
|||Vigran, T.E. (2008) Building Acoustics. CRC Press, Boca Raton. eww150213lx|