Calibration of parametric acoustic array

The parametric acoustic array can generate highly directional sound beam by taking advantage of the nonlinear effect in air. The directivity of the sound beam can be controlled by applying phased array techniques, which have been proven to be adequate both in theory and experiment. However, significant mismatches are observed between the theoretical beampatterns and the measured directivities due to the system errors incurred at different stages of implementation. In this paper, we propose a beamsteering structure for the parametric acoustic array that compensates for four types of system errors, namely, the delay error, the weight error, the spacing error, and the wavenumber error. These system errors can be reduced by using a combined optimization approach of Monte Carlo method and nonlinear least squares method. Experimental results are presented to show the feasibility of this proposed beamsteering structure and the optimization approach.