Controlling incident sound fields with source arrays in free space and through apertures

Abstract

The active control of an incident sound field with an array of secondary sources is a fun-damental problem in active control. In this paper the optimal performance of an infinite array of secondary sources in controlling a plane incident sound wave is first considered in free space. An analytic solution for normal incidence plane waves is presented, indi-cating a clear cut-off frequency for good performance, when the separation distance be-tween the uniformly-spaced sources is equal to a wavelength. This result is then compared with numerical simulations of controlling the sound power radiated through an open ap-erture in a rigid wall, subject to an incident plane wave and using an array of secondary sources in the aperture. In this case the diffraction through the aperture becomes important when the size of the window is compatible with the acoustic wavelength, in which case only a few sources are necessary for good control. When the size of the window is large compared to the wavelength, and diffraction is less important but more secondary sources need to be used for good control, the results become similar to those for the free field problem.

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Identifiers

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

ORCID for Chuang Shi: orcid.org/0000-0002-1517-2775

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