Sound radiation by flat layered structures

Abstract

Sound radiation by flat layered structures oscillating under the effect of random fractal forces has been investigated theoretically. The reciprocity theorem formulated earlier by the author has been used and the boundary problem solution is put down in an integral form. It is demonstrated that an acoustical pattern in the far wave field is determined by the product of the structure transmission coefficient and the Fourier spectrum of external forces. Random fractal forces are characterized by a correlation function of mass fractal dimension. It has been established that the fractal dimension of average intensity of acoustic field fluctuations coincides with the fractal dimension of the forces. Single-layer (a thin plate), double-layer, and triple-layer elastic structures are considered. It is noted that the singularity spectrum of an acoustic field radiated by a wall in a turbulent flow coincides with the singularity spectrum of wall pressure fluctuations. [This research is supported by the Russian Foundation for Basic Research.]