Multi-frequency calculation is usually very time-consuming due to the repeated numerical integration for numerous frequencies in acoustic scattering or radiation problems. A series expansion method has been proposed to speed up this process just by taking the frequency-dependent terms out of the integral sign. However, this method, constrained by the number of truncation terms, is only applicable to low and medium frequencies and/or small-size structures. This paper develops an improved series expansion method that can be employed in a wider frequency band and larger-scale problems but with less computing expense. In the present method, the frequency-dependent term kr in the integral kernel is firstly transformed into the range from −π to π due to the periodicity of sine and cosine functions. Afterwards, truncation error would be kept reasonably small while the number of expansion terms would not increase with kr. Test cases of acoustic radiation from a pulsating sphere and a cat's eye structure are conducted and numerical results show significant reduction of computational time but suffering little accuracy loss for multi-frequency problems with this approach.
An analytical model is developed to investigate the vibro-acoustic response of a double-walled cylindrical shell with the inner wall perforated when excited by the external turbulent boundary layer (TBL) pressure fluctuations. The shell motion is governed by the Donnell’s thin shell theory, and the mean particle velocity model is employed to describe the boundary condition between the microperforated shell and fluid media. Numerical results indicate that the transmission loss (TL) for the configuration of microperforating the inner wall could be larger than that for the conventional solid double-walled cylindrical shell with and without the core of porous material over a wide frequency range. Comparison between TL results with excitations from the TBL and the acoustic diffuse field (ADF) shows that with the thought of microperforating the inner shell, to reduce the acoustical excitation will be of more importance than the flow excitation over the ring frequency for a quiet interior space. Parametric studies illustrate that the perforation ratio is the main factor affecting the sound insulation performance through the total reactance.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.