Design of a conformal acoustic parametric array

The acoustic parametric array exploits the nonlinearity of air to create an audible sound beam that can propagate long distances. Transmitted signals are modulated around a nominal 40 kHz carrier, creating sum and difference components as the signal propagates through air. Since attenuation is proportional to frequency squared only the low-frequency difference component remains at long distances. Current commercially available parametric arrays arrange ultrasonic transducers in a planar array to create a beam of sound that is audible at distances up to 100 m. Our goal is to create a concave parametric array to determine if the added geometrical focusing allows for tighter spatial control of the audible signal. Ultrasonic transducers were mounted on a flexible three-dimensional printed structure to create an array with a variable curvature. Simulation and experimental results are presented comparing our conformal array to two commercially available planar arrays.