A pilot system for acoustic tunnel monitoring

At the Austrian main road S35 inside a tunnel near Kirchdorf the worldwide first acoustic tunnel monitoring system (AKUT) has been installed. The system processes audio signals from 49 microphones located equally distributed over two tubes, each about 2.7 km in length to detect anomalies in sound which can be associated with dangerous and alarming situations. Sounds in tunnels are characterized by engine-, rolling- and flow-sounds of vehicles. Any anomalies in sound, such as vehicles crashing into the tunnel wall or into each other, squealing tires, voices (shouts) as well as anomalies in the sound of individual vehicles can be captured by microphones placed in the tunnel. This paper will give an overview of the system and advances that have been made over the AKUT demonstration system. Major achievements have been made in making the system scalable to an almost arbitrary number of audio channels. Apart from detecting alarm sounds the system can classify these alarms into “crashes”, “horns”, “lost cargo” or reject unknown alarm sounds. The paper will furthermore give an inside view of the work that had to be done to adopt the system to a tunnel with different acoustic parameters and to communicate with the control system.