A Multibeam Steerable Parametric Array Loudspeaker for Distinct Audio Content Directing

The parametric acoustic effect has gained much interest in airborne applications as parametric acoustic loudspeakers (PALs) for the unique characteristics of generating self-demodulated low-frequency acoustic waves with high directivity. The development of PAL applications currently requires advanced spatial control of demodulated audio signals for more sophisticated sound field reproduction. Targeting to enhance the control flexibility, this paper proposes an efficient, fully FPGA-based PAL system to provide multiple low-distortion audio signals of different contents to separate directions from a single PAL device. The proposed system can achieve accurate beamsteering by providing channel time delays in nanosecond resolution and can generate independent parametric beams from a time-division-multiplexing (TDM) scheme. The paper presents a compact and scalable FPGA solution for PAL in signal preprocessing, beamsteering, and multi-beam control. The proposed system is verified in simulation and demonstrative experiments for the realization of flexible steering of multiple distinct audio signals into desired directions simultaneously under the TDM control.