Experimental analysis of the steering capabilities of airborne acoustic vortices

In this work we present an analysis of the experimental acoustic fields obtained by steering an ultrasonic vortex in the free field. In particular, we have successfully steered acoustic vortices at angles between 0 degrees and 45 degrees. To do this, we have used a Phased Array System to electronically control the delays of a hexagonal array of 30 elements equally spaced (inter-element distance of 13.6 mm, larger aperture dimension of 80 mm, and central frequency of operation of 40 kHz). The acoustic measurement of the vortices was accomplished by moving a calibrated microphone on two azimuthal and transversal planes. Special attention is paid to the simultaneous generation of grating vortices.