Membrane covered duct lining for high-frequency noise attenuation: prediction using a Chebyshev collocation method.
A spectral method of Chebyshev collocation with domain decomposition is introduced for linear interaction between sound and structure in a duct lined with flexible walls backed by cavities with or without a porous material. The spectral convergence is validated by a one-dimensional problem with a closed-form analytical solution, and is then extended to the two-dimensional configuration and compared favorably against a previous method based on the Fourier-Galerkin procedure and a finite element modeling. The nonlocal, exact Dirichlet-to-Neumann boundary condition is embedded in the domain decomposition scheme without imposing extra computational burden. The scheme is applied to the problem of high-frequency sound absorption by duct lining, which is normally ineffective when the wavelength is comparable with or shorter than the duct height. When a tensioned membrane covers the lining, however, it scatters the incident plane wave into higher-order modes, which then penetrate the duct lining more easily and get dissipated. For the frequency range of f=0.3-3 studied here, f=0.5 being the first cut-on frequency of the central duct, the membrane cover is found to offer an additional 0.9 dB attenuation per unit axial distance equal to half of the duct height.
Huang
Lixi
L
Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China. lixi.huang@hku.hk
D003252:Construction Materials / Q000592:standards; D006801:Humans; D009622:Noise / Q000517:prevention & control; D009623:Noise, Occupational / Q000517:prevention & control; D013016:Sound