Word on the street ... they’re listening

Police and councils are considering monitoring conversations in the street using high-powered microphones attached to CCTV cameras.

The microphones can detect conversations 100 yards away and record aggressive exchanges before they become violent.

The devices are used at 300 sites in Holland and police, councils and transport officials in London have shown an interest in installing them before the 2012 Olympics.

The Association of Chief Police Officers has warned that a full public debate over the microphones’ impact on privacy will be needed before they can be introduced.

The equipment can pick up aggressive tones on the basis of 12 factors, including decibel level, pitch and the speed at which words are spoken. Background noise is filtered out, enabling the camera to focus on specific conversations in public places.