Proposal of a method for assessing the audibility of siren-driven alert systems

Abstract

The civil security sirens are used by the authorities in a wide range of countries to signal an imminent or ongoing threat. Even if the emitted sound level by the sirens is known, it is nevertheless difficult to evaluate their audibility across a given zone, especially in complex urban environments. An experimental protocol has been deployed around a siren installed in a city in the south of France to assess its audibility perceptually and through modelling. This protocol relies on (1) sound level measurements during source activation, using the NoiseCapture smartphone application, (2) perceptual information survey (siren audibility, perceived sound level, masking by passing vehicles), and (3) sound environment simulation using NoiseModelling. The results of this study validate the use of CNOSSOS-EU model integrated in Noise-Modelling to evaluate the audibility of a warning system located in an urban environment within a radius of 2.8 kilometers around the siren rather than the sole consideration of the distance and even if we are far from its range of validity. Finally, a metric linking audibility to modelled sound level is proposed, enabling the development of siren audibility maps in the study area.