SOUND EMISSION BY PLANE LAYERED ELASTIC STRUCTURES

Sound emission by plane layered elastic structures driven by regular a nd random forces, including forces possessing fractal properties, is c onsidered. With the reciprocity theorem earlier formulated by the auth or, the boundary problem is reduced to integral formulations. The far sound field is determined as the product of the angular spectrum (Four ier transform) of external forces and the transmission coefficient of the structure. The latter is known for the most part, or it can be imm ediately obtained from known results of the theory on sound propagatio n in layered media. For a lumped (point) harmonic force acting on a pl ane layered structure, the angular profile of the excited held follows the angular-dependent pressure-release coefficient, accurate to a con stant factor. This similarity indicates the possibility of recovering the sound transparency of structures from their radiation fields. It i s shown that the fractal dimensionality of average intensity fluctuati ons in the held, excited by a plane-layered elastic structure driven b y statistically uniform fractal forces, coincides with the fractal dim ensionality of these forces. This fact indicates that the fractal char acteristics may be obtained from a fractal analysis of the acoustic fi eld excited by the structure. Thus, the acoustic held excited by a wal l in a turbulent stream will have the same singularities as those caus ed in the multifractal structure by intermittence phenomena of a turbu lent stream.