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'Big Brother' cameras listen for fights

Sound sensors let surveillance cameras detect aggressive tones, so police can try to nip brawls in the bud.

In U.K. public places, smarter closed-circuit TV cameras have been given the ability to listen for disturbances and also keep an eye on citizens.

The system has already been put into use in the Netherlands to listen for people speaking in aggressive tones, to try to counter violent attacks in Dutch streets, prisons and railways.

The aggression detector has been fitted to CCTV cameras on the streets of Groningen and Rotterdam in the Netherlands. In the U.K., London police also are considering installing the system, said Derek van der Vorst, the director of Sound Intelligence, the company that created the technology.

The system works by putting microphones in CCTV cameras to continually analyze 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 the camera to the location of the suspect sound and investigate the situation.

"Ninety percent of violent cases start with verbal aggression," Van der Vorst said. "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 centers, Vorst added.

Everyday mutterings are not detected by the system, though, Vorst said. "You cannot push a button to hear what people are saying," he said. "And even if you could, the microphones are 3 to 4 meters above the ground, so the words cannot be heard"

Pub brawls were cut by a quarter earlier this year in Yeovil, England, when a fingerprint-before-you-drink scheme was unveiled.

Gemma Simpson of reported from London.