Disk parametric acoustic array

A parametric acoustic array, the primary field of which is a thin disk of waves spreading cylindrically between two parallel planes, is analyzed. It is shown that the half-power beamwidth of difference-frequency radiation perpendicular to the disk exceeds the beamwidth of the corresponding collimated plane wave parametric array by a factor of 1. 316. The radiated intensity is less than in the plane-wave case by a factor of α0/k, for the same total acoustic power in the primary waves, where α0 is the absorption coefficient at the mean primary frequency and k is the wavenumber at the difference frequency.