By Gemma Simpson

Smarter CCTV cameras have been given the ability to listen out for disturbances as well as keeping an eye on citizens. The system has already been deployed in the Netherlands to listen out for aggressive tones to counter violent attacks in Dutch streets, prisons and railway systems.

The aggression detector has been fitted to CCTV cameras on the streets of Groningen and Rotterdam, with UK bobbies also considering installing the system in London. The system works by putting microphones in CCTV cameras to continually analyse the sound in the surrounding area. If aggressive tones are picked up an alarm signal is automatically sent to the police, who can zoom in to the location of the suspect sound and analyse the situation.

Derek van der Vorst, director of Sound Intelligence, the company who created the technology, told silicon.com: "Ninety per cent of violent cases start with verbal aggression, with our system the police can respond a lot quicker to a violent situation."

The sound system also means fewer people can monitor more cameras in surveillance centres, Vorst added. Everyday mutterings are not detected by the system though. Vorst said: "You cannot push a button to hear what people are saying and even if you could the microphones are three to four metres above the ground so the words cannot be heard."

Vorst said the Metropolitan police have shown an interest in using such a system in London.