Active control of acoustic scattering from a passively optimised spherical shell

Abstract

At low frequencies, the sound power scattered from a spherical shell can be minimised by designing its material properties and thickness so that the mass and compressibility are the same as that of the displaced fluid. The scattered power is then dominated at higher frequencies by that due to the resonances of the structural modes of the shell, particularly the ovalling mode. The peaks in the scattered power due to structural resonances can be reduced somewhat by material damping but are more effectively attenuated with active control using structural actuators as secondary sources. Simulations are presented of the scattered sound power of such a shell when subject to feedforward control, which assumes knowledge of both the incident and scattered acoustic sound fields, and structural feedback control, which only assumes that the velocity on the surface of the sphere can be measured. The performance of the feedback controller is also examined if the structural actuators and sensors are distributed over the surface of the sphere, rather than just acting at single points.

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Identifiers

ORCID for Mihai Orita: orcid.org/0000-0001-7307-0497

ORCID for Erika Quaranta: orcid.org/0000-0002-6632-9947

ORCID for Jordan Cheer: orcid.org/0000-0002-0552-5506

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