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The objective of this paper is representation an analytical solution to calculate sound transmission loss (TL) of infinite thick transverse-isotropic cylindrical shell immersed in a fluid medium with an uniform external airflow and contains internal fluids where external sidewall of the shell excited by an oblique plane wave. In order to derive the governing equations the third-order shear deformation theory (TSDT) is used. Also, equation of motion of shell is obtained using Hamilton's principle. With solving shell vibration equations and acoustic wave equations simultaneously, the exact solution for TL is obtained. Transmission loss resultant from this solution is compared with those of other authors. The results also indicate that TSDT is more powerful than FSDT and CST, especially in high frequency and less R/h.

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In this paper, the sound behavior of a double walled composite with an intermediate porous layer has been conducted using the classical laminated plate theory (CLPT). The main objective of the paper is devoted to considering the analytical study of various boundaries on porous layers as well as parameter study on power transmission through the structure. Thus, viscous and inertia coupling in a dynamic equation, as well as stress transfer, thermal and elastic coupling of porous material are considered based on Biot theory. In addition, the equation of wave propagation are extracted according to vibration equation of composite layers. Then, with applying the various boundaries on the structures along with solving these equations simultaneously, the Transmission Loss (TL) is calculated. The analytical results are compared with both numerical ones obtained from Statistical energy Analysis (SEA) as well as empirical results and an excellent agreement is observed. The parametric studies are presented to investigate the effects of boundary conditions on TL. The results indicate that the interface of porous-composite layers as well as stacking sequences of the composite layers would play an important role in reduction of power transmission through the structure.

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Sound transmission through a double – wall circular cylindrical shell is investigated. In order to study the acoustic behavior of these kinds of thin circular cylindrical shells, an exact analytical approach is discussed in detail. Using an infinitely long thin walled circular cylindrical shell subjected to a plane wave incidence, the structure – acoustic equations based on the Donnell’s thin shell theory are obtained and transmission losses calculated by this approach are compared to the transmission losses obtained according to the Love’s theory. The comparison shows that the Donnell theory distinguishes all the frequencies in which sound transmitted inside the shell easily and it predicts the sound transmission characteristics of a thin circular cylindrical shell better than the Love’s theory especially in resonance – controlled and mass – controlled regions. Then the effects of different sound absorber materials and various gases are studied in order to fill the cylindrical shell’s gap with a material except air. The results show that high sound transmission loss and better trend can be achieved by using these sound absorber materials in double-wall circular cylindrical shells.

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In this paper, sound transmission loss through double-walled orthotropic cylindrical shells based on three-dimensional elasticity theory is investigated. Hence, the purpose of this paper is to analyze the effect of the acoustic wave incidence under two different angels on sound transmission loss through the shell. The present model is a double-walled orthotropic cylindrical shell immersed in a fluid with an infinite length, whereas the acoustic plane incident waves impinge upon the shell with two different angels of θ and δ. The state space method is used to investigate the laminate approximated model along with transfer matrix approach for modeling both walls of cylindrical shell. In order to consider the two different angles of θ and δ, the corresponding wave equations have been modified according to the wave numbers. Comparing the results obtained from presents study with those of other researchers shows an excellent agreement between the results. Moreover, the effects of different parameters on sound transmission loss through the shell have been evaluated. The results show an enhancement of sound transmission loss in double-walled cylindrical shells rather than single-walled cylindrical shells particularly in high frequency range. Also, the results indicate the dependency of sound transmission loss on both of two θ and δ angels. In other word, the variety of two incident angles may cause the significant variations in sound transmission loss.

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In the present study, the available methods of predicting the sound transmission loss through infinitely long double-walled cylindrical shells with porous layer are developed to analytically compute the sound transmission loss in triple-walled sandwich cylindrical shells in the presence of an external fluid flow. Loves’ shell theory and Lee’s method based on Biot’s theory are used to describe the motions of thin isotropic triple-walled cylindrical shell and wave propagation in the porous media, respectively. The vibro-acoustic problem for the most complicated configuration of the triple-walled sandwich cylindrical shell is formulated and solved by the transfer matrix method with appropriate boundary conditions. The total transmission loss in a diffuse field is calculated and validated by considering the effect of total internal reflection. Then the transmission loss of triple-walled cylindrical shell is compared with its double-walled counterpart of the same weight. The results generally show a superior performance in sound insulation for the case of triple-walled shell, considerably at mid-high and high frequency regions. Moreover, ten typical configurations, which involve different coupling methods between the walls and porous layers, are considered to completely study the effect of various configurations on the sound transmission properties. As will be shown, a configuration with the largest number of air gaps in its structure provides better performance in sound transmission reduction almost at the entire frequency range. The effects of external fluid flow and azimuthal angle are also studied on the sound transmission loss.

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Due to lower cost compared to field measurement, simulation of sound propagation is considerably favorable for acoustic researchers. One of most optimized methods in this regard is PE (paraboloic Equation), which gives detailed low cost results especially in the low and mid frequencies. On the other hand, most of the human interaction with the water bodies are in the so called shallow water region, where PE is the most common method of acoustic simulation. In this study, effects of environmental parameters on transmission loss are investigated in the range of the scale of few tens of kilometers. The results show subsurface flows and sound speed profile variations in the course of the range, have the least effects and bottom properties, specifically the attenuation factor, are the most effective parameter in the low frequency sound propagation. On the other side, in the range of higher frequencies (more than 1000 Hz), seasonal variation of sound speed profile has the most efficient effect