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Summary: FORMATION OF ANUNKNOWN DISCRETE
SPECTRUM IN A GENERAL SPECTRUM
OF STRUCTURES, INTERACTING WITH
FLUID
Andrei Abramian
Institute for Problems in Mechanical Engineering,
Bolshoy pr. V.O. 61,
199178 St.Petersburg, Russia
abramian@math.ipme.ru
Abstract During investigation of noise levels from large structures, such as ship
hulls, attention is usually drawn to obvious strong vibration mecha-
nisms. However, unexpected noise levels at certain frequencies may be
due to radiation from structural details, e.g. joints or walls.
As a consequence some radiation at an unexpected frequencies occurs
when the structure is operating. Three possible reasons causing the
existence of such frequencies have been investigated.
1. LOCALIZED MODES OF ELASTIC
STRUCTURES
In nite length structures with elastic mass inclusions have both con-
tinuous and real discrete spectrums [1]. A real discrete spectrum can be
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