The directional discrimination of volume arrays of electro-acoustic transducers

The directivity factor of an array of electro-acoustic transducers distributed throughout a cubical volume has been found to vary inversely as the square of the element spacing, as does the factor for the elements occupying one face of the cube. Arrays occupying the volume of a sphere, its surface, and its plane projection show directivity factors which are not inversely proportional to the number of elements but which are nearly equal. At spacings for which these arrays have useful directivity patterns there is negligible advantage in using a volume array in an isotropic noise field.