Ganged-speaker siren system with substantially uniform wavefront patterns

Abstract From the Canadian patent

Electronic outdoor warning siren systems which include a plurality of speakers arranged in one or more vertically spaced circular arrays of circumferentially spaced vertically oriented speakers to achieve substantially uniform coverage in all radial directions in a horizontal plane, and utilizing frequency variations in adjacent speakers to minimize interference between sound signals from adjacent speakers thereby permitting closer spacing of speakers than would otherwise be feasible and providing uniform omnidirectional sound propagation. The same frequency variations are also employed with a plurality of speakers oriented in the same direction and rotated through 360° to accomplish the …