Acoustic wave propagation in bent thin-walled wave guides

Theoretical analysis of sound wave propagation in structures indicates considerable amplitude reduction during transmission through a bent joint, while some build-up can be observed in front of the bend. Every type of transmitted wave (longitudinal and flexural in plane frames) is found to combine with other forms of sound propagation as a result of the deflection of the axis of the wave guide. The screening effect of the bend, in solids with arbitrary viscoelastic properties, is evident even under highly simplified assumptions, such as compatibility and equilibrium. By solving several practical problems, the attenuation due to folding of the structure is compared to the damping effect of the material, with the conclusion that the former contribution is the larger of the two. A pair of examples of insulation analysis of structures is worked out, and the results yield the particle velocity—the first step in determining the radiation pattern. The influence of dense columns in walls, of beams in plates, and of coupling effects in bent structures are examined.