 
Summary: Sound radiation from a line forced perforated elastic
sandwich panel
I. David Abrahams
Department of Mathematics, University of Manchester, Oxford Road, Manchester M13 9PL,
United Kingdom
Received 16 April 1998; revised 31 October 1998; accepted 11 March 1999
Composite barriers, consisting of thin plates separated by light matrix structures, are widely used for
fuselage construction in the aircraft industry, and in partitions in the building trade. The acoustical
properties of such materials can vary considerably by altering the interior geometry, and
perforations can be added to one or both sides. With perforations the interior cavities can act as
Helmholtz resonators, causing a substantial modification to the overall transmission and reflection
properties of such barriers. Leppington Proc. R. Soc. London, Ser. A 427, 385399 1990 devised
an effective boundary condition for a perforated sandwich plate structure, valid in the limit of low
frequency acoustical waves long compared with the typical dimensions of the hole/cavity
construction , and obtained transmission and reflection coefficients for infinite planar structures.
This article investigates the radiation properties of perforated sandwich plates by examining a
simple infinite onedimensional model employing Leppington's effective boundary condition
which is loaded by a line force or moment. The radiated far field, and unattenuated subsonic plate
wave coefficients, are found explicitly, and are plotted over a range of frequencies for two physical
configurations, namely an aluminum plate in water and in air. It is revealed that, unlike the usual
