LOW FREQUENCY ACOUSTIC TRANSMISSION THROUGH THE WALLS OF RECTANGULAR DUCTS-t

Sound attenuation in dissipative expansion chambers

Recent improvements in fiber properties combined with their broadband acoustic dissipation characteristics make such materials potentially desirable for implementation in silencers. The acoustic modelling of simple silencer geometries, such as circular or rectangular cross-sections, has been established and classified depending on the assumption of locallyor bulk-reacting lining. Morse [1] used...

Acoustic propagation in 3-D, rectangular ducts with flexible walls

In this article some analytic expressions for acoustic propagation in 3-D ducts of rectangular cross-section and with flexible walls are explored. Consideration is first given to the propagation of sound in an unlined 3-D duct formed by three rigid walls and closed by a thin elastic plate. An exact closed form expression for the fluid-structure coupled waves is presented. The effect of incorpor...

The Solution of Three Dimensional Incompressible Potential Flow Through Rectangular Ducts

Acoustic Wave propagation through multilayer Thue-Morse structures containing two, three and four materials of Cu, Al, MgO and Pb

In this paper, the acoustic wave propagation in multilayer Thue-Morse structures has theoretically been studied. The composing layers were assumed do be Cu, Al, Mgo and Pb materials. Two, three or four different materials have been used in a typical structure. By using a perpendicular incident acoustic wave, the transmission coefficient was calculated and then by its old, the frequency gaps was...

Low Frequency Noise Attenuation inside Ducts using locally resonant periodic flush mounted Steel Patches

Traditional passive noise control techniques using Helmholtz resonators have size limitations at low frequency due to the long wavelengths. Promising noise reductions, with flush mounted Stainless Steel patches with no such constraints can be obtained building on local resonance phenomenon implemented in acoustic metamaterials techniques. The objective of the current paper is to introduce local...