The ideal arrangement of the siren horns is when they stand at 180° to each other. The diffraction at the gap of the siren horns ensures omni-directional 360° sound propagation. This physical mechanism ensures that the sound also enters the acoustic shadow. From a physical point of view, the diffraction of the sound waves can be explained using the Van Huygen principle.
The horns of the ECN sirens were developed in consideration of physical laws and were subjected to extensive testing so that an optimum sound propagation is guaranteed.