Acoustic Analysis with Consideration of Damping Effects of Air Viscosity in Sound Pathway

Authors: M. Sasajima, M. Watanabe, T. Yamaguchi, Y. Kurosawa, Y. Koike

Abstract:

Sound pathways in the enclosures of small earphones are very narrow. In such narrow pathways, the speed of sound propagation and the phase of sound waves change because of the air viscosity. We have developed a new finite element method that includes the effects of damping due to air viscosity for modeling the sound pathway. This method is developed as an extension of the existing finite element method for porous sound-absorbing materials. The numerical calculation results using the proposed finite element method are validated against the existing calculation methods.

Keywords: Simulation, FEM, air viscosity, damping.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1071216

References:

[1] T. Yamaguchi, J. Tsugawa, H. Enomoto and Y. Kurosawa, "Layout of Sound Absorbing Materials in 3D Rooms Using Damping Contributions with Eigenvectors as Weight Coefficients", Journal of System Design and Dynamics, Vol. 4-1, pp. 166-176, 2010.
[2] T. Yamaguchi, Y. Kurosawa and H. Enomoto, "Damped Vibration Analysis Using Finite Element Method with Approximated Modal Damping for Automotive Double Walls with a Porous Material", Journal of Sound and Vibration, Vol. 325, pp. 436-450, 2009.
[3] M. Sasajima, T. Yamaguchi and A. Hara, "Acoustic Analysis Using Finite Element Method Considering Effects of Damping Caused by Air Viscosity in Audio Equipment", Applied Mechanics and Materials, Vol. 36, pp. 282-286, 2010.
[4] H. Utsuno, T. Tanaka, Y. Morisawa and T. Yoshimura, "Prediction of Normal Sound Absorption Coefficient for Multi-Layer Sound Absorbing Materials by Using the Boundary Element Method", Transactions of Japan Society of Mechanical Engineers, Vol. 56-532C, pp. 3248-3252, 1990.
[5] A. Craggs and J.G.Hildebrandt, "Effective densities and resistivities for acoustic propagation in narrow tubes", Journal of Sound and Vibration, Vol.92, pp321-331, 1984.
[6] M. A. Biot, "Theory of Propagation of Elastic Waves in a Fluid-Saturated Porous Solid. Ôàí. Higher Frequency Range", Journal of the Acoustical Society of America, Vol.28, pp179-191, 1956.