A. E. Ekimov
A. V. Lebedev
Inst. of Appl. Phys., Russian Acad. of Sci., Hydroacoust. Div., Nizhny Novgorod, Russia
Sound radiation by an arbitrary structure affected by discontinuities is analyzed. A discontinuity strongly influences the structure's radiation, a small inhomogeneity not being a sign of slight variations of the acoustical field. Its effect depends on the Q factor of the structure and its kind. The attention is concentrated on the analysis of peculiarities caused by the type and distribution of the discontinuities. It is shown that the greater alternation of the radiation is affected by a single, local discontinuity, while any distribution of the latter leads to a decrease of this alternation. From the obtained expressions one can easily see that thin shells are of special interest for the investigation of their radiation properties alternations under discontinuities. This report is concerned with qualitative analysis for an arbitrary structure and concrete results for the shell, whose acoustic characteristics depend on discontinuities most strongly. Because of that, most of the report is concerned with the discussion of experimental study results. The measurements were made on an initially homogeneous cylindrical shell under local mass loadings. While a vibration exciter is additional discontinuity, the reciprocity method was used for accurate measurements. The results obtained are in good agreement with the simple analysis conclusions.
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