olice and councils are considering monitoring
conversations in the street using high-powered microphones
attached to CCTV cameras, write Steven Swinford and Nicola
The microphones can detect conversations 100
yards away and record aggressive exchanges before they become
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 interest in the equipment comes amid
growing concern that Britain is becoming a “surveillance
society”. It was recently highlighted that there are more than
4.2m CCTV cameras, with the average person being filmed more
than 300 times a day. The addition of microphones would take
surveillance into uncharted territory.
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
If the aggressive behaviour continues, police
can intervene before an incident escalates. Privacy laws in
Holland limit the recording of sound to short bursts. Derek van
der Vorst, director of Sound Intelligence, the company that
created the technology, said: “It is technically capable of
being live 24 hours a day and recording 24 hours a day. It
really depends on the privacy laws in a particular country.”
Last month Martin Nanninga of VCS
Observation, the Dutch company marketing the technology, gave a
presentation to officials from Transport for London, the
Metropolitan police and the City of London police about the CCTV
system. Nanninga is to return next year for further discussions.
“There was a lot of interest in our system,
especially with security concerns about the Olympic Games in
2012. We told them about both our intelligent control room and
the aggression detection system,” Nanninga said.
In Holland more than 300 of the cameras have
been fitted in Groningen, Utrecht and Rotterdam. Locations
include city centres, benefit offices, jails, and even T-Mobile
shops. The sensitivity of the microphones is adjusted to suit
Police and local council officials are still
assessing their impact on crime, although in an initial six-week
trial in Groningen last year the cameras raised 70 genuine
alarms, resulting in four arrests.
Harry Hoetjer, head of surveillance at
Groningen police headquarters, recalled an incident where the
camera had homed in on a gang of four men who were about to
attack a passer-by. “We would not normally have detected it as
there was no camera directly viewing it,” he said.
Last Friday a Sunday Times reporter visited
the office of Sound Intelligence in Groningen to test the
system. The reporter stood in the control centre with a view of
an empty room on one of a bank of monitors. Van der Vorst
entered the room, out of sight of the camera, and began making
The camera swivelled to film him and an alarm
went off in the control room, designed to alert police to a
possible incident. “The cameras work on the principle that in an
aggressive situation the pitch goes up and the words are spoken
faster,” said van der Vorst. “The voice is not the normal flat
tone, but vibrates. It is these subtle changes that our audio
cameras can pick up on.”
Public prosecution services can use them in
court as evidence. The Dutch privacy board has already given its
approval to the system.
According to a spokesman for Richard Thomas,
Britain’s information commissioner, sound recorded by the
cameras would be treated under British law in the same way as
CCTV footage. Under the commissioner’s code of practice, audio
can be recorded for the detection, prevention of crime and
apprehension and prosecution of offenders. It cannot be used for
recording private conversations.
Graeme Gerrard, chairman of the chief police
officers’ video and CCTV working group, said: “In the UK this is
a new step. Clearly there is somebody or something monitoring
people speaking in the street, and before we were to engage in
that technology there would be a number of legal obstacles.
“We would need to have a debate as to whether
or not this is something the public think would be a reasonable
use of the technology. The other issue is around the capacity of
the police service to deal with this.”