Improving the super resolution focusing above a two-dimensional Helmholtz resonator array using particle velocity decomposition of time reversal focusing

Abstract

Super resolution is possible using resonators placed in the near field of time reversal focusing. This presentation addresses the problem that a two-dimensional Helmholtz resonator array in a three-dimensional reverberant environment has limited ability to produce a high-resolution spatial focus in the time reversal focusing of audible sound. Acoustic waves propagating out-of-plane with the resonator array are not as strongly modified by the resonators, partially negating the effect of the resonators. The use of a two-dimensional waveguide limits the out-of-plane propagation, leading to improved resolution. It is also shown that post processing using an orthogonal particle velocity decomposition of a spatial scan of the focusing can limit out-of-plane particle motion in the near field of the array, which bypasses the effect of the unwanted third spatial dimension of propagation. Each of these techniques results in a pressure field focus reconstruction that has a higher spatial resolution.