In the last decades we have assisted to a growing need for security in many public environments. This consideration has led the proliferation of cameras and microphones, which represent a suitable solution for their relative low cost of maintenance, the possibility of installing them virtually everywhere and, finally, the capability of analyzing more complex events. The main limitation of this traditional audio-video surveillance systems lies in the so called psychological overcharge issue of the human operators responsible for security, that causes a decrease in their capabilities to analyze...