Phase Control of Parametric Array Loudspeaker by Optimizing Sideband Weights

In this paper, we propose a method for controlling the directivity of parametric speakers by optimizing the weights for the sideband signals. By setting the weights for the sideband signals in the SSB modulation to the optimum values, the directivity of the audible sound can be controlled to be ideal. The sum of squares of the difference between the directivity of the reproduced audible sound and the ideal directivity is used as an evaluation function for weight design, and the weights are updated to minimize the evaluation function by the quasi-Newton method. Through the numerical analysis of the sound pressure distribution of PAL beam control using the weights designed by the proposed method, it is demonstrated that the grating lobes are suppressed and the acoustic beam is formed to the desired direction compared with the case using the weights designed by the conventional Chebyshev function.