Creation of Large Quiet Zones in the Presence of Acoustical Levitation Traps

Paper in proceeding, 2021

We propose a method to generate an acoustical levitation trap at the same time as suppressing the sound in a multi-wavelength region of space. The method uses a spherical basis expansion of the sound field in the quiet zone, calculated by translating individual source expansions of elements in a transducer array. We show that it is possible to control the size of the quiet zone with the truncation order of the expansion, and explain the trade-off between field suppression in the quiet zone and stiffness loss of the levitation trap. Measurements of a generated sound field show the existence of a region of lower sound pressure. Simulations demonstrate a contrast up to 50 dB and sizes up to 60 mm for a 256 element array.