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Convention Paper

The Focal Shift Phenomena for Focused Source Reproduction Using Loudspeaker Arrays

Authors: Oldfield, Robert; Drumm, Ian

AES Convention 137 · Paper 9099 · October 2014

Abstract

The focal shift phenomenon in optics describes how the position of the focus point in a focusing system is not simply defined by geometrical ray-based models but is affected by diffraction and is consequently a function of the size of the lens and the frequency of the light. The same effect is also observed in acoustics when looking at the focused field using physical focusing reflectors. This paper describes the focal shift phenomenon applied to the reproduction of focused sources with sound field synthesis systems, and presents a formula for the prediction of the actual rendered focal point position and also a frequency dependent positional correction for the improved rendering of a focused source with a given loudspeaker setup.

Details

Published in
AES Convention 137
AES Convention
137
Paper number
9099
Publication date
October 6, 2014
Session subject
Spatial Audio
Affiliation
University of Salford, Salford, Greater Manchester, UK (See document for exact affiliation information.)
Type
Convention Paper